| 1 | /* |
| 2 | * linux/mm/vmscan.c |
| 3 | * |
| 4 | * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds |
| 5 | * |
| 6 | * Swap reorganised 29.12.95, Stephen Tweedie. |
| 7 | * kswapd added: 7.1.96 sct |
| 8 | * Removed kswapd_ctl limits, and swap out as many pages as needed |
| 9 | * to bring the system back to freepages.high: 2.4.97, Rik van Riel. |
| 10 | * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com). |
| 11 | * Multiqueue VM started 5.8.00, Rik van Riel. |
| 12 | */ |
| 13 | |
| 14 | #include <linux/mm.h> |
| 15 | #include <linux/module.h> |
| 16 | #include <linux/gfp.h> |
| 17 | #include <linux/kernel_stat.h> |
| 18 | #include <linux/swap.h> |
| 19 | #include <linux/pagemap.h> |
| 20 | #include <linux/init.h> |
| 21 | #include <linux/highmem.h> |
| 22 | #include <linux/vmpressure.h> |
| 23 | #include <linux/vmstat.h> |
| 24 | #include <linux/file.h> |
| 25 | #include <linux/writeback.h> |
| 26 | #include <linux/blkdev.h> |
| 27 | #include <linux/buffer_head.h> /* for try_to_release_page(), |
| 28 | buffer_heads_over_limit */ |
| 29 | #include <linux/mm_inline.h> |
| 30 | #include <linux/backing-dev.h> |
| 31 | #include <linux/rmap.h> |
| 32 | #include <linux/topology.h> |
| 33 | #include <linux/cpu.h> |
| 34 | #include <linux/cpuset.h> |
| 35 | #include <linux/compaction.h> |
| 36 | #include <linux/notifier.h> |
| 37 | #include <linux/rwsem.h> |
| 38 | #include <linux/delay.h> |
| 39 | #include <linux/kthread.h> |
| 40 | #include <linux/freezer.h> |
| 41 | #include <linux/memcontrol.h> |
| 42 | #include <linux/delayacct.h> |
| 43 | #include <linux/sysctl.h> |
| 44 | #include <linux/oom.h> |
| 45 | #include <linux/prefetch.h> |
| 46 | |
| 47 | #include <asm/tlbflush.h> |
| 48 | #include <asm/div64.h> |
| 49 | |
| 50 | #include <linux/swapops.h> |
| 51 | |
| 52 | #include "internal.h" |
| 53 | |
| 54 | #define CREATE_TRACE_POINTS |
| 55 | #include <trace/events/vmscan.h> |
| 56 | |
| 57 | struct scan_control { |
| 58 | /* Incremented by the number of inactive pages that were scanned */ |
| 59 | unsigned long nr_scanned; |
| 60 | |
| 61 | /* Number of pages freed so far during a call to shrink_zones() */ |
| 62 | unsigned long nr_reclaimed; |
| 63 | |
| 64 | /* How many pages shrink_list() should reclaim */ |
| 65 | unsigned long nr_to_reclaim; |
| 66 | |
| 67 | unsigned long hibernation_mode; |
| 68 | |
| 69 | /* This context's GFP mask */ |
| 70 | gfp_t gfp_mask; |
| 71 | |
| 72 | int may_writepage; |
| 73 | |
| 74 | /* Can mapped pages be reclaimed? */ |
| 75 | int may_unmap; |
| 76 | |
| 77 | /* Can pages be swapped as part of reclaim? */ |
| 78 | int may_swap; |
| 79 | |
| 80 | int order; |
| 81 | |
| 82 | /* Scan (total_size >> priority) pages at once */ |
| 83 | int priority; |
| 84 | |
| 85 | /* |
| 86 | * The memory cgroup that hit its limit and as a result is the |
| 87 | * primary target of this reclaim invocation. |
| 88 | */ |
| 89 | struct mem_cgroup *target_mem_cgroup; |
| 90 | |
| 91 | /* |
| 92 | * Nodemask of nodes allowed by the caller. If NULL, all nodes |
| 93 | * are scanned. |
| 94 | */ |
| 95 | nodemask_t *nodemask; |
| 96 | }; |
| 97 | |
| 98 | #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru)) |
| 99 | |
| 100 | #ifdef ARCH_HAS_PREFETCH |
| 101 | #define prefetch_prev_lru_page(_page, _base, _field) \ |
| 102 | do { \ |
| 103 | if ((_page)->lru.prev != _base) { \ |
| 104 | struct page *prev; \ |
| 105 | \ |
| 106 | prev = lru_to_page(&(_page->lru)); \ |
| 107 | prefetch(&prev->_field); \ |
| 108 | } \ |
| 109 | } while (0) |
| 110 | #else |
| 111 | #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0) |
| 112 | #endif |
| 113 | |
| 114 | #ifdef ARCH_HAS_PREFETCHW |
| 115 | #define prefetchw_prev_lru_page(_page, _base, _field) \ |
| 116 | do { \ |
| 117 | if ((_page)->lru.prev != _base) { \ |
| 118 | struct page *prev; \ |
| 119 | \ |
| 120 | prev = lru_to_page(&(_page->lru)); \ |
| 121 | prefetchw(&prev->_field); \ |
| 122 | } \ |
| 123 | } while (0) |
| 124 | #else |
| 125 | #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0) |
| 126 | #endif |
| 127 | |
| 128 | /* |
| 129 | * From 0 .. 100. Higher means more swappy. |
| 130 | */ |
| 131 | int vm_swappiness = 60; |
| 132 | unsigned long vm_total_pages; /* The total number of pages which the VM controls */ |
| 133 | |
| 134 | static LIST_HEAD(shrinker_list); |
| 135 | static DECLARE_RWSEM(shrinker_rwsem); |
| 136 | |
| 137 | #ifdef CONFIG_MEMCG |
| 138 | static bool global_reclaim(struct scan_control *sc) |
| 139 | { |
| 140 | return !sc->target_mem_cgroup; |
| 141 | } |
| 142 | #else |
| 143 | static bool global_reclaim(struct scan_control *sc) |
| 144 | { |
| 145 | return true; |
| 146 | } |
| 147 | #endif |
| 148 | |
| 149 | static unsigned long get_lru_size(struct lruvec *lruvec, enum lru_list lru) |
| 150 | { |
| 151 | if (!mem_cgroup_disabled()) |
| 152 | return mem_cgroup_get_lru_size(lruvec, lru); |
| 153 | |
| 154 | return zone_page_state(lruvec_zone(lruvec), NR_LRU_BASE + lru); |
| 155 | } |
| 156 | |
| 157 | /* |
| 158 | * Add a shrinker callback to be called from the vm |
| 159 | */ |
| 160 | void register_shrinker(struct shrinker *shrinker) |
| 161 | { |
| 162 | atomic_long_set(&shrinker->nr_in_batch, 0); |
| 163 | down_write(&shrinker_rwsem); |
| 164 | list_add_tail(&shrinker->list, &shrinker_list); |
| 165 | up_write(&shrinker_rwsem); |
| 166 | } |
| 167 | EXPORT_SYMBOL(register_shrinker); |
| 168 | |
| 169 | /* |
| 170 | * Remove one |
| 171 | */ |
| 172 | void unregister_shrinker(struct shrinker *shrinker) |
| 173 | { |
| 174 | down_write(&shrinker_rwsem); |
| 175 | list_del(&shrinker->list); |
| 176 | up_write(&shrinker_rwsem); |
| 177 | } |
| 178 | EXPORT_SYMBOL(unregister_shrinker); |
| 179 | |
| 180 | static inline int do_shrinker_shrink(struct shrinker *shrinker, |
| 181 | struct shrink_control *sc, |
| 182 | unsigned long nr_to_scan) |
| 183 | { |
| 184 | sc->nr_to_scan = nr_to_scan; |
| 185 | return (*shrinker->shrink)(shrinker, sc); |
| 186 | } |
| 187 | |
| 188 | #define SHRINK_BATCH 128 |
| 189 | /* |
| 190 | * Call the shrink functions to age shrinkable caches |
| 191 | * |
| 192 | * Here we assume it costs one seek to replace a lru page and that it also |
| 193 | * takes a seek to recreate a cache object. With this in mind we age equal |
| 194 | * percentages of the lru and ageable caches. This should balance the seeks |
| 195 | * generated by these structures. |
| 196 | * |
| 197 | * If the vm encountered mapped pages on the LRU it increase the pressure on |
| 198 | * slab to avoid swapping. |
| 199 | * |
| 200 | * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits. |
| 201 | * |
| 202 | * `lru_pages' represents the number of on-LRU pages in all the zones which |
| 203 | * are eligible for the caller's allocation attempt. It is used for balancing |
| 204 | * slab reclaim versus page reclaim. |
| 205 | * |
| 206 | * Returns the number of slab objects which we shrunk. |
| 207 | */ |
| 208 | unsigned long shrink_slab(struct shrink_control *shrink, |
| 209 | unsigned long nr_pages_scanned, |
| 210 | unsigned long lru_pages) |
| 211 | { |
| 212 | struct shrinker *shrinker; |
| 213 | unsigned long ret = 0; |
| 214 | |
| 215 | if (nr_pages_scanned == 0) |
| 216 | nr_pages_scanned = SWAP_CLUSTER_MAX; |
| 217 | |
| 218 | if (!down_read_trylock(&shrinker_rwsem)) { |
| 219 | /* Assume we'll be able to shrink next time */ |
| 220 | ret = 1; |
| 221 | goto out; |
| 222 | } |
| 223 | |
| 224 | list_for_each_entry(shrinker, &shrinker_list, list) { |
| 225 | unsigned long long delta; |
| 226 | long total_scan; |
| 227 | long max_pass; |
| 228 | int shrink_ret = 0; |
| 229 | long nr; |
| 230 | long new_nr; |
| 231 | long batch_size = shrinker->batch ? shrinker->batch |
| 232 | : SHRINK_BATCH; |
| 233 | |
| 234 | max_pass = do_shrinker_shrink(shrinker, shrink, 0); |
| 235 | if (max_pass <= 0) |
| 236 | continue; |
| 237 | |
| 238 | /* |
| 239 | * copy the current shrinker scan count into a local variable |
| 240 | * and zero it so that other concurrent shrinker invocations |
| 241 | * don't also do this scanning work. |
| 242 | */ |
| 243 | nr = atomic_long_xchg(&shrinker->nr_in_batch, 0); |
| 244 | |
| 245 | total_scan = nr; |
| 246 | delta = (4 * nr_pages_scanned) / shrinker->seeks; |
| 247 | delta *= max_pass; |
| 248 | do_div(delta, lru_pages + 1); |
| 249 | total_scan += delta; |
| 250 | if (total_scan < 0) { |
| 251 | printk(KERN_ERR "shrink_slab: %pF negative objects to " |
| 252 | "delete nr=%ld\n", |
| 253 | shrinker->shrink, total_scan); |
| 254 | total_scan = max_pass; |
| 255 | } |
| 256 | |
| 257 | /* |
| 258 | * We need to avoid excessive windup on filesystem shrinkers |
| 259 | * due to large numbers of GFP_NOFS allocations causing the |
| 260 | * shrinkers to return -1 all the time. This results in a large |
| 261 | * nr being built up so when a shrink that can do some work |
| 262 | * comes along it empties the entire cache due to nr >>> |
| 263 | * max_pass. This is bad for sustaining a working set in |
| 264 | * memory. |
| 265 | * |
| 266 | * Hence only allow the shrinker to scan the entire cache when |
| 267 | * a large delta change is calculated directly. |
| 268 | */ |
| 269 | if (delta < max_pass / 4) |
| 270 | total_scan = min(total_scan, max_pass / 2); |
| 271 | |
| 272 | /* |
| 273 | * Avoid risking looping forever due to too large nr value: |
| 274 | * never try to free more than twice the estimate number of |
| 275 | * freeable entries. |
| 276 | */ |
| 277 | if (total_scan > max_pass * 2) |
| 278 | total_scan = max_pass * 2; |
| 279 | |
| 280 | trace_mm_shrink_slab_start(shrinker, shrink, nr, |
| 281 | nr_pages_scanned, lru_pages, |
| 282 | max_pass, delta, total_scan); |
| 283 | |
| 284 | while (total_scan >= batch_size) { |
| 285 | int nr_before; |
| 286 | |
| 287 | nr_before = do_shrinker_shrink(shrinker, shrink, 0); |
| 288 | shrink_ret = do_shrinker_shrink(shrinker, shrink, |
| 289 | batch_size); |
| 290 | if (shrink_ret == -1) |
| 291 | break; |
| 292 | if (shrink_ret < nr_before) |
| 293 | ret += nr_before - shrink_ret; |
| 294 | count_vm_events(SLABS_SCANNED, batch_size); |
| 295 | total_scan -= batch_size; |
| 296 | |
| 297 | cond_resched(); |
| 298 | } |
| 299 | |
| 300 | /* |
| 301 | * move the unused scan count back into the shrinker in a |
| 302 | * manner that handles concurrent updates. If we exhausted the |
| 303 | * scan, there is no need to do an update. |
| 304 | */ |
| 305 | if (total_scan > 0) |
| 306 | new_nr = atomic_long_add_return(total_scan, |
| 307 | &shrinker->nr_in_batch); |
| 308 | else |
| 309 | new_nr = atomic_long_read(&shrinker->nr_in_batch); |
| 310 | |
| 311 | trace_mm_shrink_slab_end(shrinker, shrink_ret, nr, new_nr); |
| 312 | } |
| 313 | up_read(&shrinker_rwsem); |
| 314 | out: |
| 315 | cond_resched(); |
| 316 | return ret; |
| 317 | } |
| 318 | |
| 319 | static inline int is_page_cache_freeable(struct page *page) |
| 320 | { |
| 321 | /* |
| 322 | * A freeable page cache page is referenced only by the caller |
| 323 | * that isolated the page, the page cache radix tree and |
| 324 | * optional buffer heads at page->private. |
| 325 | */ |
| 326 | return page_count(page) - page_has_private(page) == 2; |
| 327 | } |
| 328 | |
| 329 | static int may_write_to_queue(struct backing_dev_info *bdi, |
| 330 | struct scan_control *sc) |
| 331 | { |
| 332 | if (current->flags & PF_SWAPWRITE) |
| 333 | return 1; |
| 334 | if (!bdi_write_congested(bdi)) |
| 335 | return 1; |
| 336 | if (bdi == current->backing_dev_info) |
| 337 | return 1; |
| 338 | return 0; |
| 339 | } |
| 340 | |
| 341 | /* |
| 342 | * We detected a synchronous write error writing a page out. Probably |
| 343 | * -ENOSPC. We need to propagate that into the address_space for a subsequent |
| 344 | * fsync(), msync() or close(). |
| 345 | * |
| 346 | * The tricky part is that after writepage we cannot touch the mapping: nothing |
| 347 | * prevents it from being freed up. But we have a ref on the page and once |
| 348 | * that page is locked, the mapping is pinned. |
| 349 | * |
| 350 | * We're allowed to run sleeping lock_page() here because we know the caller has |
| 351 | * __GFP_FS. |
| 352 | */ |
| 353 | static void handle_write_error(struct address_space *mapping, |
| 354 | struct page *page, int error) |
| 355 | { |
| 356 | lock_page(page); |
| 357 | if (page_mapping(page) == mapping) |
| 358 | mapping_set_error(mapping, error); |
| 359 | unlock_page(page); |
| 360 | } |
| 361 | |
| 362 | /* possible outcome of pageout() */ |
| 363 | typedef enum { |
| 364 | /* failed to write page out, page is locked */ |
| 365 | PAGE_KEEP, |
| 366 | /* move page to the active list, page is locked */ |
| 367 | PAGE_ACTIVATE, |
| 368 | /* page has been sent to the disk successfully, page is unlocked */ |
| 369 | PAGE_SUCCESS, |
| 370 | /* page is clean and locked */ |
| 371 | PAGE_CLEAN, |
| 372 | } pageout_t; |
| 373 | |
| 374 | /* |
| 375 | * pageout is called by shrink_page_list() for each dirty page. |
| 376 | * Calls ->writepage(). |
| 377 | */ |
| 378 | static pageout_t pageout(struct page *page, struct address_space *mapping, |
| 379 | struct scan_control *sc) |
| 380 | { |
| 381 | /* |
| 382 | * If the page is dirty, only perform writeback if that write |
| 383 | * will be non-blocking. To prevent this allocation from being |
| 384 | * stalled by pagecache activity. But note that there may be |
| 385 | * stalls if we need to run get_block(). We could test |
| 386 | * PagePrivate for that. |
| 387 | * |
| 388 | * If this process is currently in __generic_file_aio_write() against |
| 389 | * this page's queue, we can perform writeback even if that |
| 390 | * will block. |
| 391 | * |
| 392 | * If the page is swapcache, write it back even if that would |
| 393 | * block, for some throttling. This happens by accident, because |
| 394 | * swap_backing_dev_info is bust: it doesn't reflect the |
| 395 | * congestion state of the swapdevs. Easy to fix, if needed. |
| 396 | */ |
| 397 | if (!is_page_cache_freeable(page)) |
| 398 | return PAGE_KEEP; |
| 399 | if (!mapping) { |
| 400 | /* |
| 401 | * Some data journaling orphaned pages can have |
| 402 | * page->mapping == NULL while being dirty with clean buffers. |
| 403 | */ |
| 404 | if (page_has_private(page)) { |
| 405 | if (try_to_free_buffers(page)) { |
| 406 | ClearPageDirty(page); |
| 407 | printk("%s: orphaned page\n", __func__); |
| 408 | return PAGE_CLEAN; |
| 409 | } |
| 410 | } |
| 411 | return PAGE_KEEP; |
| 412 | } |
| 413 | if (mapping->a_ops->writepage == NULL) |
| 414 | return PAGE_ACTIVATE; |
| 415 | if (!may_write_to_queue(mapping->backing_dev_info, sc)) |
| 416 | return PAGE_KEEP; |
| 417 | |
| 418 | if (clear_page_dirty_for_io(page)) { |
| 419 | int res; |
| 420 | struct writeback_control wbc = { |
| 421 | .sync_mode = WB_SYNC_NONE, |
| 422 | .nr_to_write = SWAP_CLUSTER_MAX, |
| 423 | .range_start = 0, |
| 424 | .range_end = LLONG_MAX, |
| 425 | .for_reclaim = 1, |
| 426 | }; |
| 427 | |
| 428 | SetPageReclaim(page); |
| 429 | res = mapping->a_ops->writepage(page, &wbc); |
| 430 | if (res < 0) |
| 431 | handle_write_error(mapping, page, res); |
| 432 | if (res == AOP_WRITEPAGE_ACTIVATE) { |
| 433 | ClearPageReclaim(page); |
| 434 | return PAGE_ACTIVATE; |
| 435 | } |
| 436 | |
| 437 | if (!PageWriteback(page)) { |
| 438 | /* synchronous write or broken a_ops? */ |
| 439 | ClearPageReclaim(page); |
| 440 | } |
| 441 | trace_mm_vmscan_writepage(page, trace_reclaim_flags(page)); |
| 442 | inc_zone_page_state(page, NR_VMSCAN_WRITE); |
| 443 | return PAGE_SUCCESS; |
| 444 | } |
| 445 | |
| 446 | return PAGE_CLEAN; |
| 447 | } |
| 448 | |
| 449 | /* |
| 450 | * Same as remove_mapping, but if the page is removed from the mapping, it |
| 451 | * gets returned with a refcount of 0. |
| 452 | */ |
| 453 | static int __remove_mapping(struct address_space *mapping, struct page *page) |
| 454 | { |
| 455 | BUG_ON(!PageLocked(page)); |
| 456 | BUG_ON(mapping != page_mapping(page)); |
| 457 | |
| 458 | spin_lock_irq(&mapping->tree_lock); |
| 459 | /* |
| 460 | * The non racy check for a busy page. |
| 461 | * |
| 462 | * Must be careful with the order of the tests. When someone has |
| 463 | * a ref to the page, it may be possible that they dirty it then |
| 464 | * drop the reference. So if PageDirty is tested before page_count |
| 465 | * here, then the following race may occur: |
| 466 | * |
| 467 | * get_user_pages(&page); |
| 468 | * [user mapping goes away] |
| 469 | * write_to(page); |
| 470 | * !PageDirty(page) [good] |
| 471 | * SetPageDirty(page); |
| 472 | * put_page(page); |
| 473 | * !page_count(page) [good, discard it] |
| 474 | * |
| 475 | * [oops, our write_to data is lost] |
| 476 | * |
| 477 | * Reversing the order of the tests ensures such a situation cannot |
| 478 | * escape unnoticed. The smp_rmb is needed to ensure the page->flags |
| 479 | * load is not satisfied before that of page->_count. |
| 480 | * |
| 481 | * Note that if SetPageDirty is always performed via set_page_dirty, |
| 482 | * and thus under tree_lock, then this ordering is not required. |
| 483 | */ |
| 484 | if (!page_freeze_refs(page, 2)) |
| 485 | goto cannot_free; |
| 486 | /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */ |
| 487 | if (unlikely(PageDirty(page))) { |
| 488 | page_unfreeze_refs(page, 2); |
| 489 | goto cannot_free; |
| 490 | } |
| 491 | |
| 492 | if (PageSwapCache(page)) { |
| 493 | swp_entry_t swap = { .val = page_private(page) }; |
| 494 | __delete_from_swap_cache(page); |
| 495 | spin_unlock_irq(&mapping->tree_lock); |
| 496 | swapcache_free(swap, page); |
| 497 | } else { |
| 498 | void (*freepage)(struct page *); |
| 499 | |
| 500 | freepage = mapping->a_ops->freepage; |
| 501 | |
| 502 | __delete_from_page_cache(page); |
| 503 | spin_unlock_irq(&mapping->tree_lock); |
| 504 | mem_cgroup_uncharge_cache_page(page); |
| 505 | |
| 506 | if (freepage != NULL) |
| 507 | freepage(page); |
| 508 | } |
| 509 | |
| 510 | return 1; |
| 511 | |
| 512 | cannot_free: |
| 513 | spin_unlock_irq(&mapping->tree_lock); |
| 514 | return 0; |
| 515 | } |
| 516 | |
| 517 | /* |
| 518 | * Attempt to detach a locked page from its ->mapping. If it is dirty or if |
| 519 | * someone else has a ref on the page, abort and return 0. If it was |
| 520 | * successfully detached, return 1. Assumes the caller has a single ref on |
| 521 | * this page. |
| 522 | */ |
| 523 | int remove_mapping(struct address_space *mapping, struct page *page) |
| 524 | { |
| 525 | if (__remove_mapping(mapping, page)) { |
| 526 | /* |
| 527 | * Unfreezing the refcount with 1 rather than 2 effectively |
| 528 | * drops the pagecache ref for us without requiring another |
| 529 | * atomic operation. |
| 530 | */ |
| 531 | page_unfreeze_refs(page, 1); |
| 532 | return 1; |
| 533 | } |
| 534 | return 0; |
| 535 | } |
| 536 | |
| 537 | /** |
| 538 | * putback_lru_page - put previously isolated page onto appropriate LRU list |
| 539 | * @page: page to be put back to appropriate lru list |
| 540 | * |
| 541 | * Add previously isolated @page to appropriate LRU list. |
| 542 | * Page may still be unevictable for other reasons. |
| 543 | * |
| 544 | * lru_lock must not be held, interrupts must be enabled. |
| 545 | */ |
| 546 | void putback_lru_page(struct page *page) |
| 547 | { |
| 548 | int lru; |
| 549 | int active = !!TestClearPageActive(page); |
| 550 | int was_unevictable = PageUnevictable(page); |
| 551 | |
| 552 | VM_BUG_ON(PageLRU(page)); |
| 553 | |
| 554 | redo: |
| 555 | ClearPageUnevictable(page); |
| 556 | |
| 557 | if (page_evictable(page)) { |
| 558 | /* |
| 559 | * For evictable pages, we can use the cache. |
| 560 | * In event of a race, worst case is we end up with an |
| 561 | * unevictable page on [in]active list. |
| 562 | * We know how to handle that. |
| 563 | */ |
| 564 | lru = active + page_lru_base_type(page); |
| 565 | lru_cache_add_lru(page, lru); |
| 566 | } else { |
| 567 | /* |
| 568 | * Put unevictable pages directly on zone's unevictable |
| 569 | * list. |
| 570 | */ |
| 571 | lru = LRU_UNEVICTABLE; |
| 572 | add_page_to_unevictable_list(page); |
| 573 | /* |
| 574 | * When racing with an mlock or AS_UNEVICTABLE clearing |
| 575 | * (page is unlocked) make sure that if the other thread |
| 576 | * does not observe our setting of PG_lru and fails |
| 577 | * isolation/check_move_unevictable_pages, |
| 578 | * we see PG_mlocked/AS_UNEVICTABLE cleared below and move |
| 579 | * the page back to the evictable list. |
| 580 | * |
| 581 | * The other side is TestClearPageMlocked() or shmem_lock(). |
| 582 | */ |
| 583 | smp_mb(); |
| 584 | } |
| 585 | |
| 586 | /* |
| 587 | * page's status can change while we move it among lru. If an evictable |
| 588 | * page is on unevictable list, it never be freed. To avoid that, |
| 589 | * check after we added it to the list, again. |
| 590 | */ |
| 591 | if (lru == LRU_UNEVICTABLE && page_evictable(page)) { |
| 592 | if (!isolate_lru_page(page)) { |
| 593 | put_page(page); |
| 594 | goto redo; |
| 595 | } |
| 596 | /* This means someone else dropped this page from LRU |
| 597 | * So, it will be freed or putback to LRU again. There is |
| 598 | * nothing to do here. |
| 599 | */ |
| 600 | } |
| 601 | |
| 602 | if (was_unevictable && lru != LRU_UNEVICTABLE) |
| 603 | count_vm_event(UNEVICTABLE_PGRESCUED); |
| 604 | else if (!was_unevictable && lru == LRU_UNEVICTABLE) |
| 605 | count_vm_event(UNEVICTABLE_PGCULLED); |
| 606 | |
| 607 | put_page(page); /* drop ref from isolate */ |
| 608 | } |
| 609 | |
| 610 | enum page_references { |
| 611 | PAGEREF_RECLAIM, |
| 612 | PAGEREF_RECLAIM_CLEAN, |
| 613 | PAGEREF_KEEP, |
| 614 | PAGEREF_ACTIVATE, |
| 615 | }; |
| 616 | |
| 617 | static enum page_references page_check_references(struct page *page, |
| 618 | struct scan_control *sc) |
| 619 | { |
| 620 | int referenced_ptes, referenced_page; |
| 621 | unsigned long vm_flags; |
| 622 | |
| 623 | referenced_ptes = page_referenced(page, 1, sc->target_mem_cgroup, |
| 624 | &vm_flags); |
| 625 | referenced_page = TestClearPageReferenced(page); |
| 626 | |
| 627 | /* |
| 628 | * Mlock lost the isolation race with us. Let try_to_unmap() |
| 629 | * move the page to the unevictable list. |
| 630 | */ |
| 631 | if (vm_flags & VM_LOCKED) |
| 632 | return PAGEREF_RECLAIM; |
| 633 | |
| 634 | if (referenced_ptes) { |
| 635 | if (PageSwapBacked(page)) |
| 636 | return PAGEREF_ACTIVATE; |
| 637 | /* |
| 638 | * All mapped pages start out with page table |
| 639 | * references from the instantiating fault, so we need |
| 640 | * to look twice if a mapped file page is used more |
| 641 | * than once. |
| 642 | * |
| 643 | * Mark it and spare it for another trip around the |
| 644 | * inactive list. Another page table reference will |
| 645 | * lead to its activation. |
| 646 | * |
| 647 | * Note: the mark is set for activated pages as well |
| 648 | * so that recently deactivated but used pages are |
| 649 | * quickly recovered. |
| 650 | */ |
| 651 | SetPageReferenced(page); |
| 652 | |
| 653 | if (referenced_page || referenced_ptes > 1) |
| 654 | return PAGEREF_ACTIVATE; |
| 655 | |
| 656 | /* |
| 657 | * Activate file-backed executable pages after first usage. |
| 658 | */ |
| 659 | if (vm_flags & VM_EXEC) |
| 660 | return PAGEREF_ACTIVATE; |
| 661 | |
| 662 | return PAGEREF_KEEP; |
| 663 | } |
| 664 | |
| 665 | /* Reclaim if clean, defer dirty pages to writeback */ |
| 666 | if (referenced_page && !PageSwapBacked(page)) |
| 667 | return PAGEREF_RECLAIM_CLEAN; |
| 668 | |
| 669 | return PAGEREF_RECLAIM; |
| 670 | } |
| 671 | |
| 672 | /* |
| 673 | * shrink_page_list() returns the number of reclaimed pages |
| 674 | */ |
| 675 | static unsigned long shrink_page_list(struct list_head *page_list, |
| 676 | struct zone *zone, |
| 677 | struct scan_control *sc, |
| 678 | enum ttu_flags ttu_flags, |
| 679 | unsigned long *ret_nr_dirty, |
| 680 | unsigned long *ret_nr_writeback, |
| 681 | bool force_reclaim) |
| 682 | { |
| 683 | LIST_HEAD(ret_pages); |
| 684 | LIST_HEAD(free_pages); |
| 685 | int pgactivate = 0; |
| 686 | unsigned long nr_dirty = 0; |
| 687 | unsigned long nr_congested = 0; |
| 688 | unsigned long nr_reclaimed = 0; |
| 689 | unsigned long nr_writeback = 0; |
| 690 | |
| 691 | cond_resched(); |
| 692 | |
| 693 | mem_cgroup_uncharge_start(); |
| 694 | while (!list_empty(page_list)) { |
| 695 | struct address_space *mapping; |
| 696 | struct page *page; |
| 697 | int may_enter_fs; |
| 698 | enum page_references references = PAGEREF_RECLAIM_CLEAN; |
| 699 | |
| 700 | cond_resched(); |
| 701 | |
| 702 | page = lru_to_page(page_list); |
| 703 | list_del(&page->lru); |
| 704 | |
| 705 | if (!trylock_page(page)) |
| 706 | goto keep; |
| 707 | |
| 708 | VM_BUG_ON(PageActive(page)); |
| 709 | VM_BUG_ON(page_zone(page) != zone); |
| 710 | |
| 711 | sc->nr_scanned++; |
| 712 | |
| 713 | if (unlikely(!page_evictable(page))) |
| 714 | goto cull_mlocked; |
| 715 | |
| 716 | if (!sc->may_unmap && page_mapped(page)) |
| 717 | goto keep_locked; |
| 718 | |
| 719 | /* Double the slab pressure for mapped and swapcache pages */ |
| 720 | if (page_mapped(page) || PageSwapCache(page)) |
| 721 | sc->nr_scanned++; |
| 722 | |
| 723 | may_enter_fs = (sc->gfp_mask & __GFP_FS) || |
| 724 | (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO)); |
| 725 | |
| 726 | if (PageWriteback(page)) { |
| 727 | /* |
| 728 | * memcg doesn't have any dirty pages throttling so we |
| 729 | * could easily OOM just because too many pages are in |
| 730 | * writeback and there is nothing else to reclaim. |
| 731 | * |
| 732 | * Check __GFP_IO, certainly because a loop driver |
| 733 | * thread might enter reclaim, and deadlock if it waits |
| 734 | * on a page for which it is needed to do the write |
| 735 | * (loop masks off __GFP_IO|__GFP_FS for this reason); |
| 736 | * but more thought would probably show more reasons. |
| 737 | * |
| 738 | * Don't require __GFP_FS, since we're not going into |
| 739 | * the FS, just waiting on its writeback completion. |
| 740 | * Worryingly, ext4 gfs2 and xfs allocate pages with |
| 741 | * grab_cache_page_write_begin(,,AOP_FLAG_NOFS), so |
| 742 | * testing may_enter_fs here is liable to OOM on them. |
| 743 | */ |
| 744 | if (global_reclaim(sc) || |
| 745 | !PageReclaim(page) || !(sc->gfp_mask & __GFP_IO)) { |
| 746 | /* |
| 747 | * This is slightly racy - end_page_writeback() |
| 748 | * might have just cleared PageReclaim, then |
| 749 | * setting PageReclaim here end up interpreted |
| 750 | * as PageReadahead - but that does not matter |
| 751 | * enough to care. What we do want is for this |
| 752 | * page to have PageReclaim set next time memcg |
| 753 | * reclaim reaches the tests above, so it will |
| 754 | * then wait_on_page_writeback() to avoid OOM; |
| 755 | * and it's also appropriate in global reclaim. |
| 756 | */ |
| 757 | SetPageReclaim(page); |
| 758 | nr_writeback++; |
| 759 | goto keep_locked; |
| 760 | } |
| 761 | wait_on_page_writeback(page); |
| 762 | } |
| 763 | |
| 764 | if (!force_reclaim) |
| 765 | references = page_check_references(page, sc); |
| 766 | |
| 767 | switch (references) { |
| 768 | case PAGEREF_ACTIVATE: |
| 769 | goto activate_locked; |
| 770 | case PAGEREF_KEEP: |
| 771 | goto keep_locked; |
| 772 | case PAGEREF_RECLAIM: |
| 773 | case PAGEREF_RECLAIM_CLEAN: |
| 774 | ; /* try to reclaim the page below */ |
| 775 | } |
| 776 | |
| 777 | /* |
| 778 | * Anonymous process memory has backing store? |
| 779 | * Try to allocate it some swap space here. |
| 780 | */ |
| 781 | if (PageAnon(page) && !PageSwapCache(page)) { |
| 782 | if (!(sc->gfp_mask & __GFP_IO)) |
| 783 | goto keep_locked; |
| 784 | if (!add_to_swap(page, page_list)) |
| 785 | goto activate_locked; |
| 786 | may_enter_fs = 1; |
| 787 | } |
| 788 | |
| 789 | mapping = page_mapping(page); |
| 790 | |
| 791 | /* |
| 792 | * The page is mapped into the page tables of one or more |
| 793 | * processes. Try to unmap it here. |
| 794 | */ |
| 795 | if (page_mapped(page) && mapping) { |
| 796 | switch (try_to_unmap(page, ttu_flags)) { |
| 797 | case SWAP_FAIL: |
| 798 | goto activate_locked; |
| 799 | case SWAP_AGAIN: |
| 800 | goto keep_locked; |
| 801 | case SWAP_MLOCK: |
| 802 | goto cull_mlocked; |
| 803 | case SWAP_SUCCESS: |
| 804 | ; /* try to free the page below */ |
| 805 | } |
| 806 | } |
| 807 | |
| 808 | if (PageDirty(page)) { |
| 809 | nr_dirty++; |
| 810 | |
| 811 | /* |
| 812 | * Only kswapd can writeback filesystem pages to |
| 813 | * avoid risk of stack overflow but do not writeback |
| 814 | * unless under significant pressure. |
| 815 | */ |
| 816 | if (page_is_file_cache(page) && |
| 817 | (!current_is_kswapd() || |
| 818 | sc->priority >= DEF_PRIORITY - 2)) { |
| 819 | /* |
| 820 | * Immediately reclaim when written back. |
| 821 | * Similar in principal to deactivate_page() |
| 822 | * except we already have the page isolated |
| 823 | * and know it's dirty |
| 824 | */ |
| 825 | inc_zone_page_state(page, NR_VMSCAN_IMMEDIATE); |
| 826 | SetPageReclaim(page); |
| 827 | |
| 828 | goto keep_locked; |
| 829 | } |
| 830 | |
| 831 | if (references == PAGEREF_RECLAIM_CLEAN) |
| 832 | goto keep_locked; |
| 833 | if (!may_enter_fs) |
| 834 | goto keep_locked; |
| 835 | if (!sc->may_writepage) |
| 836 | goto keep_locked; |
| 837 | |
| 838 | /* Page is dirty, try to write it out here */ |
| 839 | switch (pageout(page, mapping, sc)) { |
| 840 | case PAGE_KEEP: |
| 841 | nr_congested++; |
| 842 | goto keep_locked; |
| 843 | case PAGE_ACTIVATE: |
| 844 | goto activate_locked; |
| 845 | case PAGE_SUCCESS: |
| 846 | if (PageWriteback(page)) |
| 847 | goto keep; |
| 848 | if (PageDirty(page)) |
| 849 | goto keep; |
| 850 | |
| 851 | /* |
| 852 | * A synchronous write - probably a ramdisk. Go |
| 853 | * ahead and try to reclaim the page. |
| 854 | */ |
| 855 | if (!trylock_page(page)) |
| 856 | goto keep; |
| 857 | if (PageDirty(page) || PageWriteback(page)) |
| 858 | goto keep_locked; |
| 859 | mapping = page_mapping(page); |
| 860 | case PAGE_CLEAN: |
| 861 | ; /* try to free the page below */ |
| 862 | } |
| 863 | } |
| 864 | |
| 865 | /* |
| 866 | * If the page has buffers, try to free the buffer mappings |
| 867 | * associated with this page. If we succeed we try to free |
| 868 | * the page as well. |
| 869 | * |
| 870 | * We do this even if the page is PageDirty(). |
| 871 | * try_to_release_page() does not perform I/O, but it is |
| 872 | * possible for a page to have PageDirty set, but it is actually |
| 873 | * clean (all its buffers are clean). This happens if the |
| 874 | * buffers were written out directly, with submit_bh(). ext3 |
| 875 | * will do this, as well as the blockdev mapping. |
| 876 | * try_to_release_page() will discover that cleanness and will |
| 877 | * drop the buffers and mark the page clean - it can be freed. |
| 878 | * |
| 879 | * Rarely, pages can have buffers and no ->mapping. These are |
| 880 | * the pages which were not successfully invalidated in |
| 881 | * truncate_complete_page(). We try to drop those buffers here |
| 882 | * and if that worked, and the page is no longer mapped into |
| 883 | * process address space (page_count == 1) it can be freed. |
| 884 | * Otherwise, leave the page on the LRU so it is swappable. |
| 885 | */ |
| 886 | if (page_has_private(page)) { |
| 887 | if (!try_to_release_page(page, sc->gfp_mask)) |
| 888 | goto activate_locked; |
| 889 | if (!mapping && page_count(page) == 1) { |
| 890 | unlock_page(page); |
| 891 | if (put_page_testzero(page)) |
| 892 | goto free_it; |
| 893 | else { |
| 894 | /* |
| 895 | * rare race with speculative reference. |
| 896 | * the speculative reference will free |
| 897 | * this page shortly, so we may |
| 898 | * increment nr_reclaimed here (and |
| 899 | * leave it off the LRU). |
| 900 | */ |
| 901 | nr_reclaimed++; |
| 902 | continue; |
| 903 | } |
| 904 | } |
| 905 | } |
| 906 | |
| 907 | if (!mapping || !__remove_mapping(mapping, page)) |
| 908 | goto keep_locked; |
| 909 | |
| 910 | /* |
| 911 | * At this point, we have no other references and there is |
| 912 | * no way to pick any more up (removed from LRU, removed |
| 913 | * from pagecache). Can use non-atomic bitops now (and |
| 914 | * we obviously don't have to worry about waking up a process |
| 915 | * waiting on the page lock, because there are no references. |
| 916 | */ |
| 917 | __clear_page_locked(page); |
| 918 | free_it: |
| 919 | nr_reclaimed++; |
| 920 | |
| 921 | /* |
| 922 | * Is there need to periodically free_page_list? It would |
| 923 | * appear not as the counts should be low |
| 924 | */ |
| 925 | list_add(&page->lru, &free_pages); |
| 926 | continue; |
| 927 | |
| 928 | cull_mlocked: |
| 929 | if (PageSwapCache(page)) |
| 930 | try_to_free_swap(page); |
| 931 | unlock_page(page); |
| 932 | putback_lru_page(page); |
| 933 | continue; |
| 934 | |
| 935 | activate_locked: |
| 936 | /* Not a candidate for swapping, so reclaim swap space. */ |
| 937 | if (PageSwapCache(page) && vm_swap_full()) |
| 938 | try_to_free_swap(page); |
| 939 | VM_BUG_ON(PageActive(page)); |
| 940 | SetPageActive(page); |
| 941 | pgactivate++; |
| 942 | keep_locked: |
| 943 | unlock_page(page); |
| 944 | keep: |
| 945 | list_add(&page->lru, &ret_pages); |
| 946 | VM_BUG_ON(PageLRU(page) || PageUnevictable(page)); |
| 947 | } |
| 948 | |
| 949 | /* |
| 950 | * Tag a zone as congested if all the dirty pages encountered were |
| 951 | * backed by a congested BDI. In this case, reclaimers should just |
| 952 | * back off and wait for congestion to clear because further reclaim |
| 953 | * will encounter the same problem |
| 954 | */ |
| 955 | if (nr_dirty && nr_dirty == nr_congested && global_reclaim(sc)) |
| 956 | zone_set_flag(zone, ZONE_CONGESTED); |
| 957 | |
| 958 | free_hot_cold_page_list(&free_pages, 1); |
| 959 | |
| 960 | list_splice(&ret_pages, page_list); |
| 961 | count_vm_events(PGACTIVATE, pgactivate); |
| 962 | mem_cgroup_uncharge_end(); |
| 963 | *ret_nr_dirty += nr_dirty; |
| 964 | *ret_nr_writeback += nr_writeback; |
| 965 | return nr_reclaimed; |
| 966 | } |
| 967 | |
| 968 | unsigned long reclaim_clean_pages_from_list(struct zone *zone, |
| 969 | struct list_head *page_list) |
| 970 | { |
| 971 | struct scan_control sc = { |
| 972 | .gfp_mask = GFP_KERNEL, |
| 973 | .priority = DEF_PRIORITY, |
| 974 | .may_unmap = 1, |
| 975 | }; |
| 976 | unsigned long ret, dummy1, dummy2; |
| 977 | struct page *page, *next; |
| 978 | LIST_HEAD(clean_pages); |
| 979 | |
| 980 | list_for_each_entry_safe(page, next, page_list, lru) { |
| 981 | if (page_is_file_cache(page) && !PageDirty(page)) { |
| 982 | ClearPageActive(page); |
| 983 | list_move(&page->lru, &clean_pages); |
| 984 | } |
| 985 | } |
| 986 | |
| 987 | ret = shrink_page_list(&clean_pages, zone, &sc, |
| 988 | TTU_UNMAP|TTU_IGNORE_ACCESS, |
| 989 | &dummy1, &dummy2, true); |
| 990 | list_splice(&clean_pages, page_list); |
| 991 | __mod_zone_page_state(zone, NR_ISOLATED_FILE, -ret); |
| 992 | return ret; |
| 993 | } |
| 994 | |
| 995 | /* |
| 996 | * Attempt to remove the specified page from its LRU. Only take this page |
| 997 | * if it is of the appropriate PageActive status. Pages which are being |
| 998 | * freed elsewhere are also ignored. |
| 999 | * |
| 1000 | * page: page to consider |
| 1001 | * mode: one of the LRU isolation modes defined above |
| 1002 | * |
| 1003 | * returns 0 on success, -ve errno on failure. |
| 1004 | */ |
| 1005 | int __isolate_lru_page(struct page *page, isolate_mode_t mode) |
| 1006 | { |
| 1007 | int ret = -EINVAL; |
| 1008 | |
| 1009 | /* Only take pages on the LRU. */ |
| 1010 | if (!PageLRU(page)) |
| 1011 | return ret; |
| 1012 | |
| 1013 | /* Compaction should not handle unevictable pages but CMA can do so */ |
| 1014 | if (PageUnevictable(page) && !(mode & ISOLATE_UNEVICTABLE)) |
| 1015 | return ret; |
| 1016 | |
| 1017 | ret = -EBUSY; |
| 1018 | |
| 1019 | /* |
| 1020 | * To minimise LRU disruption, the caller can indicate that it only |
| 1021 | * wants to isolate pages it will be able to operate on without |
| 1022 | * blocking - clean pages for the most part. |
| 1023 | * |
| 1024 | * ISOLATE_CLEAN means that only clean pages should be isolated. This |
| 1025 | * is used by reclaim when it is cannot write to backing storage |
| 1026 | * |
| 1027 | * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages |
| 1028 | * that it is possible to migrate without blocking |
| 1029 | */ |
| 1030 | if (mode & (ISOLATE_CLEAN|ISOLATE_ASYNC_MIGRATE)) { |
| 1031 | /* All the caller can do on PageWriteback is block */ |
| 1032 | if (PageWriteback(page)) |
| 1033 | return ret; |
| 1034 | |
| 1035 | if (PageDirty(page)) { |
| 1036 | struct address_space *mapping; |
| 1037 | |
| 1038 | /* ISOLATE_CLEAN means only clean pages */ |
| 1039 | if (mode & ISOLATE_CLEAN) |
| 1040 | return ret; |
| 1041 | |
| 1042 | /* |
| 1043 | * Only pages without mappings or that have a |
| 1044 | * ->migratepage callback are possible to migrate |
| 1045 | * without blocking |
| 1046 | */ |
| 1047 | mapping = page_mapping(page); |
| 1048 | if (mapping && !mapping->a_ops->migratepage) |
| 1049 | return ret; |
| 1050 | } |
| 1051 | } |
| 1052 | |
| 1053 | if ((mode & ISOLATE_UNMAPPED) && page_mapped(page)) |
| 1054 | return ret; |
| 1055 | |
| 1056 | if (likely(get_page_unless_zero(page))) { |
| 1057 | /* |
| 1058 | * Be careful not to clear PageLRU until after we're |
| 1059 | * sure the page is not being freed elsewhere -- the |
| 1060 | * page release code relies on it. |
| 1061 | */ |
| 1062 | ClearPageLRU(page); |
| 1063 | ret = 0; |
| 1064 | } |
| 1065 | |
| 1066 | return ret; |
| 1067 | } |
| 1068 | |
| 1069 | /* |
| 1070 | * zone->lru_lock is heavily contended. Some of the functions that |
| 1071 | * shrink the lists perform better by taking out a batch of pages |
| 1072 | * and working on them outside the LRU lock. |
| 1073 | * |
| 1074 | * For pagecache intensive workloads, this function is the hottest |
| 1075 | * spot in the kernel (apart from copy_*_user functions). |
| 1076 | * |
| 1077 | * Appropriate locks must be held before calling this function. |
| 1078 | * |
| 1079 | * @nr_to_scan: The number of pages to look through on the list. |
| 1080 | * @lruvec: The LRU vector to pull pages from. |
| 1081 | * @dst: The temp list to put pages on to. |
| 1082 | * @nr_scanned: The number of pages that were scanned. |
| 1083 | * @sc: The scan_control struct for this reclaim session |
| 1084 | * @mode: One of the LRU isolation modes |
| 1085 | * @lru: LRU list id for isolating |
| 1086 | * |
| 1087 | * returns how many pages were moved onto *@dst. |
| 1088 | */ |
| 1089 | static unsigned long isolate_lru_pages(unsigned long nr_to_scan, |
| 1090 | struct lruvec *lruvec, struct list_head *dst, |
| 1091 | unsigned long *nr_scanned, struct scan_control *sc, |
| 1092 | isolate_mode_t mode, enum lru_list lru) |
| 1093 | { |
| 1094 | struct list_head *src = &lruvec->lists[lru]; |
| 1095 | unsigned long nr_taken = 0; |
| 1096 | unsigned long scan; |
| 1097 | |
| 1098 | for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) { |
| 1099 | struct page *page; |
| 1100 | int nr_pages; |
| 1101 | |
| 1102 | page = lru_to_page(src); |
| 1103 | prefetchw_prev_lru_page(page, src, flags); |
| 1104 | |
| 1105 | VM_BUG_ON(!PageLRU(page)); |
| 1106 | |
| 1107 | switch (__isolate_lru_page(page, mode)) { |
| 1108 | case 0: |
| 1109 | nr_pages = hpage_nr_pages(page); |
| 1110 | mem_cgroup_update_lru_size(lruvec, lru, -nr_pages); |
| 1111 | list_move(&page->lru, dst); |
| 1112 | nr_taken += nr_pages; |
| 1113 | break; |
| 1114 | |
| 1115 | case -EBUSY: |
| 1116 | /* else it is being freed elsewhere */ |
| 1117 | list_move(&page->lru, src); |
| 1118 | continue; |
| 1119 | |
| 1120 | default: |
| 1121 | BUG(); |
| 1122 | } |
| 1123 | } |
| 1124 | |
| 1125 | *nr_scanned = scan; |
| 1126 | trace_mm_vmscan_lru_isolate(sc->order, nr_to_scan, scan, |
| 1127 | nr_taken, mode, is_file_lru(lru)); |
| 1128 | return nr_taken; |
| 1129 | } |
| 1130 | |
| 1131 | /** |
| 1132 | * isolate_lru_page - tries to isolate a page from its LRU list |
| 1133 | * @page: page to isolate from its LRU list |
| 1134 | * |
| 1135 | * Isolates a @page from an LRU list, clears PageLRU and adjusts the |
| 1136 | * vmstat statistic corresponding to whatever LRU list the page was on. |
| 1137 | * |
| 1138 | * Returns 0 if the page was removed from an LRU list. |
| 1139 | * Returns -EBUSY if the page was not on an LRU list. |
| 1140 | * |
| 1141 | * The returned page will have PageLRU() cleared. If it was found on |
| 1142 | * the active list, it will have PageActive set. If it was found on |
| 1143 | * the unevictable list, it will have the PageUnevictable bit set. That flag |
| 1144 | * may need to be cleared by the caller before letting the page go. |
| 1145 | * |
| 1146 | * The vmstat statistic corresponding to the list on which the page was |
| 1147 | * found will be decremented. |
| 1148 | * |
| 1149 | * Restrictions: |
| 1150 | * (1) Must be called with an elevated refcount on the page. This is a |
| 1151 | * fundamentnal difference from isolate_lru_pages (which is called |
| 1152 | * without a stable reference). |
| 1153 | * (2) the lru_lock must not be held. |
| 1154 | * (3) interrupts must be enabled. |
| 1155 | */ |
| 1156 | int isolate_lru_page(struct page *page) |
| 1157 | { |
| 1158 | int ret = -EBUSY; |
| 1159 | |
| 1160 | VM_BUG_ON(!page_count(page)); |
| 1161 | |
| 1162 | if (PageLRU(page)) { |
| 1163 | struct zone *zone = page_zone(page); |
| 1164 | struct lruvec *lruvec; |
| 1165 | |
| 1166 | spin_lock_irq(&zone->lru_lock); |
| 1167 | lruvec = mem_cgroup_page_lruvec(page, zone); |
| 1168 | if (PageLRU(page)) { |
| 1169 | int lru = page_lru(page); |
| 1170 | get_page(page); |
| 1171 | ClearPageLRU(page); |
| 1172 | del_page_from_lru_list(page, lruvec, lru); |
| 1173 | ret = 0; |
| 1174 | } |
| 1175 | spin_unlock_irq(&zone->lru_lock); |
| 1176 | } |
| 1177 | return ret; |
| 1178 | } |
| 1179 | |
| 1180 | /* |
| 1181 | * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and |
| 1182 | * then get resheduled. When there are massive number of tasks doing page |
| 1183 | * allocation, such sleeping direct reclaimers may keep piling up on each CPU, |
| 1184 | * the LRU list will go small and be scanned faster than necessary, leading to |
| 1185 | * unnecessary swapping, thrashing and OOM. |
| 1186 | */ |
| 1187 | static int too_many_isolated(struct zone *zone, int file, |
| 1188 | struct scan_control *sc) |
| 1189 | { |
| 1190 | unsigned long inactive, isolated; |
| 1191 | |
| 1192 | if (current_is_kswapd()) |
| 1193 | return 0; |
| 1194 | |
| 1195 | if (!global_reclaim(sc)) |
| 1196 | return 0; |
| 1197 | |
| 1198 | if (file) { |
| 1199 | inactive = zone_page_state(zone, NR_INACTIVE_FILE); |
| 1200 | isolated = zone_page_state(zone, NR_ISOLATED_FILE); |
| 1201 | } else { |
| 1202 | inactive = zone_page_state(zone, NR_INACTIVE_ANON); |
| 1203 | isolated = zone_page_state(zone, NR_ISOLATED_ANON); |
| 1204 | } |
| 1205 | |
| 1206 | /* |
| 1207 | * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they |
| 1208 | * won't get blocked by normal direct-reclaimers, forming a circular |
| 1209 | * deadlock. |
| 1210 | */ |
| 1211 | if ((sc->gfp_mask & GFP_IOFS) == GFP_IOFS) |
| 1212 | inactive >>= 3; |
| 1213 | |
| 1214 | return isolated > inactive; |
| 1215 | } |
| 1216 | |
| 1217 | static noinline_for_stack void |
| 1218 | putback_inactive_pages(struct lruvec *lruvec, struct list_head *page_list) |
| 1219 | { |
| 1220 | struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat; |
| 1221 | struct zone *zone = lruvec_zone(lruvec); |
| 1222 | LIST_HEAD(pages_to_free); |
| 1223 | |
| 1224 | /* |
| 1225 | * Put back any unfreeable pages. |
| 1226 | */ |
| 1227 | while (!list_empty(page_list)) { |
| 1228 | struct page *page = lru_to_page(page_list); |
| 1229 | int lru; |
| 1230 | |
| 1231 | VM_BUG_ON(PageLRU(page)); |
| 1232 | list_del(&page->lru); |
| 1233 | if (unlikely(!page_evictable(page))) { |
| 1234 | spin_unlock_irq(&zone->lru_lock); |
| 1235 | putback_lru_page(page); |
| 1236 | spin_lock_irq(&zone->lru_lock); |
| 1237 | continue; |
| 1238 | } |
| 1239 | |
| 1240 | lruvec = mem_cgroup_page_lruvec(page, zone); |
| 1241 | |
| 1242 | SetPageLRU(page); |
| 1243 | lru = page_lru(page); |
| 1244 | add_page_to_lru_list(page, lruvec, lru); |
| 1245 | |
| 1246 | if (is_active_lru(lru)) { |
| 1247 | int file = is_file_lru(lru); |
| 1248 | int numpages = hpage_nr_pages(page); |
| 1249 | reclaim_stat->recent_rotated[file] += numpages; |
| 1250 | } |
| 1251 | if (put_page_testzero(page)) { |
| 1252 | __ClearPageLRU(page); |
| 1253 | __ClearPageActive(page); |
| 1254 | del_page_from_lru_list(page, lruvec, lru); |
| 1255 | |
| 1256 | if (unlikely(PageCompound(page))) { |
| 1257 | spin_unlock_irq(&zone->lru_lock); |
| 1258 | (*get_compound_page_dtor(page))(page); |
| 1259 | spin_lock_irq(&zone->lru_lock); |
| 1260 | } else |
| 1261 | list_add(&page->lru, &pages_to_free); |
| 1262 | } |
| 1263 | } |
| 1264 | |
| 1265 | /* |
| 1266 | * To save our caller's stack, now use input list for pages to free. |
| 1267 | */ |
| 1268 | list_splice(&pages_to_free, page_list); |
| 1269 | } |
| 1270 | |
| 1271 | /* |
| 1272 | * shrink_inactive_list() is a helper for shrink_zone(). It returns the number |
| 1273 | * of reclaimed pages |
| 1274 | */ |
| 1275 | static noinline_for_stack unsigned long |
| 1276 | shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec, |
| 1277 | struct scan_control *sc, enum lru_list lru) |
| 1278 | { |
| 1279 | LIST_HEAD(page_list); |
| 1280 | unsigned long nr_scanned; |
| 1281 | unsigned long nr_reclaimed = 0; |
| 1282 | unsigned long nr_taken; |
| 1283 | unsigned long nr_dirty = 0; |
| 1284 | unsigned long nr_writeback = 0; |
| 1285 | isolate_mode_t isolate_mode = 0; |
| 1286 | int file = is_file_lru(lru); |
| 1287 | struct zone *zone = lruvec_zone(lruvec); |
| 1288 | struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat; |
| 1289 | |
| 1290 | while (unlikely(too_many_isolated(zone, file, sc))) { |
| 1291 | congestion_wait(BLK_RW_ASYNC, HZ/10); |
| 1292 | |
| 1293 | /* We are about to die and free our memory. Return now. */ |
| 1294 | if (fatal_signal_pending(current)) |
| 1295 | return SWAP_CLUSTER_MAX; |
| 1296 | } |
| 1297 | |
| 1298 | lru_add_drain(); |
| 1299 | |
| 1300 | if (!sc->may_unmap) |
| 1301 | isolate_mode |= ISOLATE_UNMAPPED; |
| 1302 | if (!sc->may_writepage) |
| 1303 | isolate_mode |= ISOLATE_CLEAN; |
| 1304 | |
| 1305 | spin_lock_irq(&zone->lru_lock); |
| 1306 | |
| 1307 | nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &page_list, |
| 1308 | &nr_scanned, sc, isolate_mode, lru); |
| 1309 | |
| 1310 | __mod_zone_page_state(zone, NR_LRU_BASE + lru, -nr_taken); |
| 1311 | __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken); |
| 1312 | |
| 1313 | if (global_reclaim(sc)) { |
| 1314 | zone->pages_scanned += nr_scanned; |
| 1315 | if (current_is_kswapd()) |
| 1316 | __count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scanned); |
| 1317 | else |
| 1318 | __count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scanned); |
| 1319 | } |
| 1320 | spin_unlock_irq(&zone->lru_lock); |
| 1321 | |
| 1322 | if (nr_taken == 0) |
| 1323 | return 0; |
| 1324 | |
| 1325 | nr_reclaimed = shrink_page_list(&page_list, zone, sc, TTU_UNMAP, |
| 1326 | &nr_dirty, &nr_writeback, false); |
| 1327 | |
| 1328 | spin_lock_irq(&zone->lru_lock); |
| 1329 | |
| 1330 | reclaim_stat->recent_scanned[file] += nr_taken; |
| 1331 | |
| 1332 | if (global_reclaim(sc)) { |
| 1333 | if (current_is_kswapd()) |
| 1334 | __count_zone_vm_events(PGSTEAL_KSWAPD, zone, |
| 1335 | nr_reclaimed); |
| 1336 | else |
| 1337 | __count_zone_vm_events(PGSTEAL_DIRECT, zone, |
| 1338 | nr_reclaimed); |
| 1339 | } |
| 1340 | |
| 1341 | putback_inactive_pages(lruvec, &page_list); |
| 1342 | |
| 1343 | __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken); |
| 1344 | |
| 1345 | spin_unlock_irq(&zone->lru_lock); |
| 1346 | |
| 1347 | free_hot_cold_page_list(&page_list, 1); |
| 1348 | |
| 1349 | /* |
| 1350 | * If reclaim is isolating dirty pages under writeback, it implies |
| 1351 | * that the long-lived page allocation rate is exceeding the page |
| 1352 | * laundering rate. Either the global limits are not being effective |
| 1353 | * at throttling processes due to the page distribution throughout |
| 1354 | * zones or there is heavy usage of a slow backing device. The |
| 1355 | * only option is to throttle from reclaim context which is not ideal |
| 1356 | * as there is no guarantee the dirtying process is throttled in the |
| 1357 | * same way balance_dirty_pages() manages. |
| 1358 | * |
| 1359 | * This scales the number of dirty pages that must be under writeback |
| 1360 | * before throttling depending on priority. It is a simple backoff |
| 1361 | * function that has the most effect in the range DEF_PRIORITY to |
| 1362 | * DEF_PRIORITY-2 which is the priority reclaim is considered to be |
| 1363 | * in trouble and reclaim is considered to be in trouble. |
| 1364 | * |
| 1365 | * DEF_PRIORITY 100% isolated pages must be PageWriteback to throttle |
| 1366 | * DEF_PRIORITY-1 50% must be PageWriteback |
| 1367 | * DEF_PRIORITY-2 25% must be PageWriteback, kswapd in trouble |
| 1368 | * ... |
| 1369 | * DEF_PRIORITY-6 For SWAP_CLUSTER_MAX isolated pages, throttle if any |
| 1370 | * isolated page is PageWriteback |
| 1371 | */ |
| 1372 | if (nr_writeback && nr_writeback >= |
| 1373 | (nr_taken >> (DEF_PRIORITY - sc->priority))) |
| 1374 | wait_iff_congested(zone, BLK_RW_ASYNC, HZ/10); |
| 1375 | |
| 1376 | trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id, |
| 1377 | zone_idx(zone), |
| 1378 | nr_scanned, nr_reclaimed, |
| 1379 | sc->priority, |
| 1380 | trace_shrink_flags(file)); |
| 1381 | return nr_reclaimed; |
| 1382 | } |
| 1383 | |
| 1384 | /* |
| 1385 | * This moves pages from the active list to the inactive list. |
| 1386 | * |
| 1387 | * We move them the other way if the page is referenced by one or more |
| 1388 | * processes, from rmap. |
| 1389 | * |
| 1390 | * If the pages are mostly unmapped, the processing is fast and it is |
| 1391 | * appropriate to hold zone->lru_lock across the whole operation. But if |
| 1392 | * the pages are mapped, the processing is slow (page_referenced()) so we |
| 1393 | * should drop zone->lru_lock around each page. It's impossible to balance |
| 1394 | * this, so instead we remove the pages from the LRU while processing them. |
| 1395 | * It is safe to rely on PG_active against the non-LRU pages in here because |
| 1396 | * nobody will play with that bit on a non-LRU page. |
| 1397 | * |
| 1398 | * The downside is that we have to touch page->_count against each page. |
| 1399 | * But we had to alter page->flags anyway. |
| 1400 | */ |
| 1401 | |
| 1402 | static void move_active_pages_to_lru(struct lruvec *lruvec, |
| 1403 | struct list_head *list, |
| 1404 | struct list_head *pages_to_free, |
| 1405 | enum lru_list lru) |
| 1406 | { |
| 1407 | struct zone *zone = lruvec_zone(lruvec); |
| 1408 | unsigned long pgmoved = 0; |
| 1409 | struct page *page; |
| 1410 | int nr_pages; |
| 1411 | |
| 1412 | while (!list_empty(list)) { |
| 1413 | page = lru_to_page(list); |
| 1414 | lruvec = mem_cgroup_page_lruvec(page, zone); |
| 1415 | |
| 1416 | VM_BUG_ON(PageLRU(page)); |
| 1417 | SetPageLRU(page); |
| 1418 | |
| 1419 | nr_pages = hpage_nr_pages(page); |
| 1420 | mem_cgroup_update_lru_size(lruvec, lru, nr_pages); |
| 1421 | list_move(&page->lru, &lruvec->lists[lru]); |
| 1422 | pgmoved += nr_pages; |
| 1423 | |
| 1424 | if (put_page_testzero(page)) { |
| 1425 | __ClearPageLRU(page); |
| 1426 | __ClearPageActive(page); |
| 1427 | del_page_from_lru_list(page, lruvec, lru); |
| 1428 | |
| 1429 | if (unlikely(PageCompound(page))) { |
| 1430 | spin_unlock_irq(&zone->lru_lock); |
| 1431 | (*get_compound_page_dtor(page))(page); |
| 1432 | spin_lock_irq(&zone->lru_lock); |
| 1433 | } else |
| 1434 | list_add(&page->lru, pages_to_free); |
| 1435 | } |
| 1436 | } |
| 1437 | __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved); |
| 1438 | if (!is_active_lru(lru)) |
| 1439 | __count_vm_events(PGDEACTIVATE, pgmoved); |
| 1440 | } |
| 1441 | |
| 1442 | static void shrink_active_list(unsigned long nr_to_scan, |
| 1443 | struct lruvec *lruvec, |
| 1444 | struct scan_control *sc, |
| 1445 | enum lru_list lru) |
| 1446 | { |
| 1447 | unsigned long nr_taken; |
| 1448 | unsigned long nr_scanned; |
| 1449 | unsigned long vm_flags; |
| 1450 | LIST_HEAD(l_hold); /* The pages which were snipped off */ |
| 1451 | LIST_HEAD(l_active); |
| 1452 | LIST_HEAD(l_inactive); |
| 1453 | struct page *page; |
| 1454 | struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat; |
| 1455 | unsigned long nr_rotated = 0; |
| 1456 | isolate_mode_t isolate_mode = 0; |
| 1457 | int file = is_file_lru(lru); |
| 1458 | struct zone *zone = lruvec_zone(lruvec); |
| 1459 | |
| 1460 | lru_add_drain(); |
| 1461 | |
| 1462 | if (!sc->may_unmap) |
| 1463 | isolate_mode |= ISOLATE_UNMAPPED; |
| 1464 | if (!sc->may_writepage) |
| 1465 | isolate_mode |= ISOLATE_CLEAN; |
| 1466 | |
| 1467 | spin_lock_irq(&zone->lru_lock); |
| 1468 | |
| 1469 | nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &l_hold, |
| 1470 | &nr_scanned, sc, isolate_mode, lru); |
| 1471 | if (global_reclaim(sc)) |
| 1472 | zone->pages_scanned += nr_scanned; |
| 1473 | |
| 1474 | reclaim_stat->recent_scanned[file] += nr_taken; |
| 1475 | |
| 1476 | __count_zone_vm_events(PGREFILL, zone, nr_scanned); |
| 1477 | __mod_zone_page_state(zone, NR_LRU_BASE + lru, -nr_taken); |
| 1478 | __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken); |
| 1479 | spin_unlock_irq(&zone->lru_lock); |
| 1480 | |
| 1481 | while (!list_empty(&l_hold)) { |
| 1482 | cond_resched(); |
| 1483 | page = lru_to_page(&l_hold); |
| 1484 | list_del(&page->lru); |
| 1485 | |
| 1486 | if (unlikely(!page_evictable(page))) { |
| 1487 | putback_lru_page(page); |
| 1488 | continue; |
| 1489 | } |
| 1490 | |
| 1491 | if (unlikely(buffer_heads_over_limit)) { |
| 1492 | if (page_has_private(page) && trylock_page(page)) { |
| 1493 | if (page_has_private(page)) |
| 1494 | try_to_release_page(page, 0); |
| 1495 | unlock_page(page); |
| 1496 | } |
| 1497 | } |
| 1498 | |
| 1499 | if (page_referenced(page, 0, sc->target_mem_cgroup, |
| 1500 | &vm_flags)) { |
| 1501 | nr_rotated += hpage_nr_pages(page); |
| 1502 | /* |
| 1503 | * Identify referenced, file-backed active pages and |
| 1504 | * give them one more trip around the active list. So |
| 1505 | * that executable code get better chances to stay in |
| 1506 | * memory under moderate memory pressure. Anon pages |
| 1507 | * are not likely to be evicted by use-once streaming |
| 1508 | * IO, plus JVM can create lots of anon VM_EXEC pages, |
| 1509 | * so we ignore them here. |
| 1510 | */ |
| 1511 | if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) { |
| 1512 | list_add(&page->lru, &l_active); |
| 1513 | continue; |
| 1514 | } |
| 1515 | } |
| 1516 | |
| 1517 | ClearPageActive(page); /* we are de-activating */ |
| 1518 | list_add(&page->lru, &l_inactive); |
| 1519 | } |
| 1520 | |
| 1521 | /* |
| 1522 | * Move pages back to the lru list. |
| 1523 | */ |
| 1524 | spin_lock_irq(&zone->lru_lock); |
| 1525 | /* |
| 1526 | * Count referenced pages from currently used mappings as rotated, |
| 1527 | * even though only some of them are actually re-activated. This |
| 1528 | * helps balance scan pressure between file and anonymous pages in |
| 1529 | * get_scan_ratio. |
| 1530 | */ |
| 1531 | reclaim_stat->recent_rotated[file] += nr_rotated; |
| 1532 | |
| 1533 | move_active_pages_to_lru(lruvec, &l_active, &l_hold, lru); |
| 1534 | move_active_pages_to_lru(lruvec, &l_inactive, &l_hold, lru - LRU_ACTIVE); |
| 1535 | __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken); |
| 1536 | spin_unlock_irq(&zone->lru_lock); |
| 1537 | |
| 1538 | free_hot_cold_page_list(&l_hold, 1); |
| 1539 | } |
| 1540 | |
| 1541 | #ifdef CONFIG_SWAP |
| 1542 | static int inactive_anon_is_low_global(struct zone *zone) |
| 1543 | { |
| 1544 | unsigned long active, inactive; |
| 1545 | |
| 1546 | active = zone_page_state(zone, NR_ACTIVE_ANON); |
| 1547 | inactive = zone_page_state(zone, NR_INACTIVE_ANON); |
| 1548 | |
| 1549 | if (inactive * zone->inactive_ratio < active) |
| 1550 | return 1; |
| 1551 | |
| 1552 | return 0; |
| 1553 | } |
| 1554 | |
| 1555 | /** |
| 1556 | * inactive_anon_is_low - check if anonymous pages need to be deactivated |
| 1557 | * @lruvec: LRU vector to check |
| 1558 | * |
| 1559 | * Returns true if the zone does not have enough inactive anon pages, |
| 1560 | * meaning some active anon pages need to be deactivated. |
| 1561 | */ |
| 1562 | static int inactive_anon_is_low(struct lruvec *lruvec) |
| 1563 | { |
| 1564 | /* |
| 1565 | * If we don't have swap space, anonymous page deactivation |
| 1566 | * is pointless. |
| 1567 | */ |
| 1568 | if (!total_swap_pages) |
| 1569 | return 0; |
| 1570 | |
| 1571 | if (!mem_cgroup_disabled()) |
| 1572 | return mem_cgroup_inactive_anon_is_low(lruvec); |
| 1573 | |
| 1574 | return inactive_anon_is_low_global(lruvec_zone(lruvec)); |
| 1575 | } |
| 1576 | #else |
| 1577 | static inline int inactive_anon_is_low(struct lruvec *lruvec) |
| 1578 | { |
| 1579 | return 0; |
| 1580 | } |
| 1581 | #endif |
| 1582 | |
| 1583 | /** |
| 1584 | * inactive_file_is_low - check if file pages need to be deactivated |
| 1585 | * @lruvec: LRU vector to check |
| 1586 | * |
| 1587 | * When the system is doing streaming IO, memory pressure here |
| 1588 | * ensures that active file pages get deactivated, until more |
| 1589 | * than half of the file pages are on the inactive list. |
| 1590 | * |
| 1591 | * Once we get to that situation, protect the system's working |
| 1592 | * set from being evicted by disabling active file page aging. |
| 1593 | * |
| 1594 | * This uses a different ratio than the anonymous pages, because |
| 1595 | * the page cache uses a use-once replacement algorithm. |
| 1596 | */ |
| 1597 | static int inactive_file_is_low(struct lruvec *lruvec) |
| 1598 | { |
| 1599 | unsigned long inactive; |
| 1600 | unsigned long active; |
| 1601 | |
| 1602 | inactive = get_lru_size(lruvec, LRU_INACTIVE_FILE); |
| 1603 | active = get_lru_size(lruvec, LRU_ACTIVE_FILE); |
| 1604 | |
| 1605 | return active > inactive; |
| 1606 | } |
| 1607 | |
| 1608 | static int inactive_list_is_low(struct lruvec *lruvec, enum lru_list lru) |
| 1609 | { |
| 1610 | if (is_file_lru(lru)) |
| 1611 | return inactive_file_is_low(lruvec); |
| 1612 | else |
| 1613 | return inactive_anon_is_low(lruvec); |
| 1614 | } |
| 1615 | |
| 1616 | static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan, |
| 1617 | struct lruvec *lruvec, struct scan_control *sc) |
| 1618 | { |
| 1619 | if (is_active_lru(lru)) { |
| 1620 | if (inactive_list_is_low(lruvec, lru)) |
| 1621 | shrink_active_list(nr_to_scan, lruvec, sc, lru); |
| 1622 | return 0; |
| 1623 | } |
| 1624 | |
| 1625 | return shrink_inactive_list(nr_to_scan, lruvec, sc, lru); |
| 1626 | } |
| 1627 | |
| 1628 | static int vmscan_swappiness(struct scan_control *sc) |
| 1629 | { |
| 1630 | if (global_reclaim(sc)) |
| 1631 | return vm_swappiness; |
| 1632 | return mem_cgroup_swappiness(sc->target_mem_cgroup); |
| 1633 | } |
| 1634 | |
| 1635 | enum scan_balance { |
| 1636 | SCAN_EQUAL, |
| 1637 | SCAN_FRACT, |
| 1638 | SCAN_ANON, |
| 1639 | SCAN_FILE, |
| 1640 | }; |
| 1641 | |
| 1642 | /* |
| 1643 | * Determine how aggressively the anon and file LRU lists should be |
| 1644 | * scanned. The relative value of each set of LRU lists is determined |
| 1645 | * by looking at the fraction of the pages scanned we did rotate back |
| 1646 | * onto the active list instead of evict. |
| 1647 | * |
| 1648 | * nr[0] = anon inactive pages to scan; nr[1] = anon active pages to scan |
| 1649 | * nr[2] = file inactive pages to scan; nr[3] = file active pages to scan |
| 1650 | */ |
| 1651 | static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc, |
| 1652 | unsigned long *nr) |
| 1653 | { |
| 1654 | struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat; |
| 1655 | u64 fraction[2]; |
| 1656 | u64 denominator = 0; /* gcc */ |
| 1657 | struct zone *zone = lruvec_zone(lruvec); |
| 1658 | unsigned long anon_prio, file_prio; |
| 1659 | enum scan_balance scan_balance; |
| 1660 | unsigned long anon, file, free; |
| 1661 | bool force_scan = false; |
| 1662 | unsigned long ap, fp; |
| 1663 | enum lru_list lru; |
| 1664 | |
| 1665 | /* |
| 1666 | * If the zone or memcg is small, nr[l] can be 0. This |
| 1667 | * results in no scanning on this priority and a potential |
| 1668 | * priority drop. Global direct reclaim can go to the next |
| 1669 | * zone and tends to have no problems. Global kswapd is for |
| 1670 | * zone balancing and it needs to scan a minimum amount. When |
| 1671 | * reclaiming for a memcg, a priority drop can cause high |
| 1672 | * latencies, so it's better to scan a minimum amount there as |
| 1673 | * well. |
| 1674 | */ |
| 1675 | if (current_is_kswapd() && zone->all_unreclaimable) |
| 1676 | force_scan = true; |
| 1677 | if (!global_reclaim(sc)) |
| 1678 | force_scan = true; |
| 1679 | |
| 1680 | /* If we have no swap space, do not bother scanning anon pages. */ |
| 1681 | if (!sc->may_swap || (get_nr_swap_pages() <= 0)) { |
| 1682 | scan_balance = SCAN_FILE; |
| 1683 | goto out; |
| 1684 | } |
| 1685 | |
| 1686 | /* |
| 1687 | * Global reclaim will swap to prevent OOM even with no |
| 1688 | * swappiness, but memcg users want to use this knob to |
| 1689 | * disable swapping for individual groups completely when |
| 1690 | * using the memory controller's swap limit feature would be |
| 1691 | * too expensive. |
| 1692 | */ |
| 1693 | if (!global_reclaim(sc) && !vmscan_swappiness(sc)) { |
| 1694 | scan_balance = SCAN_FILE; |
| 1695 | goto out; |
| 1696 | } |
| 1697 | |
| 1698 | /* |
| 1699 | * Do not apply any pressure balancing cleverness when the |
| 1700 | * system is close to OOM, scan both anon and file equally |
| 1701 | * (unless the swappiness setting disagrees with swapping). |
| 1702 | */ |
| 1703 | if (!sc->priority && vmscan_swappiness(sc)) { |
| 1704 | scan_balance = SCAN_EQUAL; |
| 1705 | goto out; |
| 1706 | } |
| 1707 | |
| 1708 | anon = get_lru_size(lruvec, LRU_ACTIVE_ANON) + |
| 1709 | get_lru_size(lruvec, LRU_INACTIVE_ANON); |
| 1710 | file = get_lru_size(lruvec, LRU_ACTIVE_FILE) + |
| 1711 | get_lru_size(lruvec, LRU_INACTIVE_FILE); |
| 1712 | |
| 1713 | /* |
| 1714 | * If it's foreseeable that reclaiming the file cache won't be |
| 1715 | * enough to get the zone back into a desirable shape, we have |
| 1716 | * to swap. Better start now and leave the - probably heavily |
| 1717 | * thrashing - remaining file pages alone. |
| 1718 | */ |
| 1719 | if (global_reclaim(sc)) { |
| 1720 | free = zone_page_state(zone, NR_FREE_PAGES); |
| 1721 | if (unlikely(file + free <= high_wmark_pages(zone))) { |
| 1722 | scan_balance = SCAN_ANON; |
| 1723 | goto out; |
| 1724 | } |
| 1725 | } |
| 1726 | |
| 1727 | /* |
| 1728 | * There is enough inactive page cache, do not reclaim |
| 1729 | * anything from the anonymous working set right now. |
| 1730 | */ |
| 1731 | if (!inactive_file_is_low(lruvec)) { |
| 1732 | scan_balance = SCAN_FILE; |
| 1733 | goto out; |
| 1734 | } |
| 1735 | |
| 1736 | scan_balance = SCAN_FRACT; |
| 1737 | |
| 1738 | /* |
| 1739 | * With swappiness at 100, anonymous and file have the same priority. |
| 1740 | * This scanning priority is essentially the inverse of IO cost. |
| 1741 | */ |
| 1742 | anon_prio = vmscan_swappiness(sc); |
| 1743 | file_prio = 200 - anon_prio; |
| 1744 | |
| 1745 | /* |
| 1746 | * OK, so we have swap space and a fair amount of page cache |
| 1747 | * pages. We use the recently rotated / recently scanned |
| 1748 | * ratios to determine how valuable each cache is. |
| 1749 | * |
| 1750 | * Because workloads change over time (and to avoid overflow) |
| 1751 | * we keep these statistics as a floating average, which ends |
| 1752 | * up weighing recent references more than old ones. |
| 1753 | * |
| 1754 | * anon in [0], file in [1] |
| 1755 | */ |
| 1756 | spin_lock_irq(&zone->lru_lock); |
| 1757 | if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) { |
| 1758 | reclaim_stat->recent_scanned[0] /= 2; |
| 1759 | reclaim_stat->recent_rotated[0] /= 2; |
| 1760 | } |
| 1761 | |
| 1762 | if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) { |
| 1763 | reclaim_stat->recent_scanned[1] /= 2; |
| 1764 | reclaim_stat->recent_rotated[1] /= 2; |
| 1765 | } |
| 1766 | |
| 1767 | /* |
| 1768 | * The amount of pressure on anon vs file pages is inversely |
| 1769 | * proportional to the fraction of recently scanned pages on |
| 1770 | * each list that were recently referenced and in active use. |
| 1771 | */ |
| 1772 | ap = anon_prio * (reclaim_stat->recent_scanned[0] + 1); |
| 1773 | ap /= reclaim_stat->recent_rotated[0] + 1; |
| 1774 | |
| 1775 | fp = file_prio * (reclaim_stat->recent_scanned[1] + 1); |
| 1776 | fp /= reclaim_stat->recent_rotated[1] + 1; |
| 1777 | spin_unlock_irq(&zone->lru_lock); |
| 1778 | |
| 1779 | fraction[0] = ap; |
| 1780 | fraction[1] = fp; |
| 1781 | denominator = ap + fp + 1; |
| 1782 | out: |
| 1783 | for_each_evictable_lru(lru) { |
| 1784 | int file = is_file_lru(lru); |
| 1785 | unsigned long size; |
| 1786 | unsigned long scan; |
| 1787 | |
| 1788 | size = get_lru_size(lruvec, lru); |
| 1789 | scan = size >> sc->priority; |
| 1790 | |
| 1791 | if (!scan && force_scan) |
| 1792 | scan = min(size, SWAP_CLUSTER_MAX); |
| 1793 | |
| 1794 | switch (scan_balance) { |
| 1795 | case SCAN_EQUAL: |
| 1796 | /* Scan lists relative to size */ |
| 1797 | break; |
| 1798 | case SCAN_FRACT: |
| 1799 | /* |
| 1800 | * Scan types proportional to swappiness and |
| 1801 | * their relative recent reclaim efficiency. |
| 1802 | */ |
| 1803 | scan = div64_u64(scan * fraction[file], denominator); |
| 1804 | break; |
| 1805 | case SCAN_FILE: |
| 1806 | case SCAN_ANON: |
| 1807 | /* Scan one type exclusively */ |
| 1808 | if ((scan_balance == SCAN_FILE) != file) |
| 1809 | scan = 0; |
| 1810 | break; |
| 1811 | default: |
| 1812 | /* Look ma, no brain */ |
| 1813 | BUG(); |
| 1814 | } |
| 1815 | nr[lru] = scan; |
| 1816 | } |
| 1817 | } |
| 1818 | |
| 1819 | /* |
| 1820 | * This is a basic per-zone page freer. Used by both kswapd and direct reclaim. |
| 1821 | */ |
| 1822 | static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc) |
| 1823 | { |
| 1824 | unsigned long nr[NR_LRU_LISTS]; |
| 1825 | unsigned long targets[NR_LRU_LISTS]; |
| 1826 | unsigned long nr_to_scan; |
| 1827 | enum lru_list lru; |
| 1828 | unsigned long nr_reclaimed = 0; |
| 1829 | unsigned long nr_to_reclaim = sc->nr_to_reclaim; |
| 1830 | struct blk_plug plug; |
| 1831 | bool scan_adjusted = false; |
| 1832 | |
| 1833 | get_scan_count(lruvec, sc, nr); |
| 1834 | |
| 1835 | /* Record the original scan target for proportional adjustments later */ |
| 1836 | memcpy(targets, nr, sizeof(nr)); |
| 1837 | |
| 1838 | blk_start_plug(&plug); |
| 1839 | while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] || |
| 1840 | nr[LRU_INACTIVE_FILE]) { |
| 1841 | unsigned long nr_anon, nr_file, percentage; |
| 1842 | unsigned long nr_scanned; |
| 1843 | |
| 1844 | for_each_evictable_lru(lru) { |
| 1845 | if (nr[lru]) { |
| 1846 | nr_to_scan = min(nr[lru], SWAP_CLUSTER_MAX); |
| 1847 | nr[lru] -= nr_to_scan; |
| 1848 | |
| 1849 | nr_reclaimed += shrink_list(lru, nr_to_scan, |
| 1850 | lruvec, sc); |
| 1851 | } |
| 1852 | } |
| 1853 | |
| 1854 | if (nr_reclaimed < nr_to_reclaim || scan_adjusted) |
| 1855 | continue; |
| 1856 | |
| 1857 | /* |
| 1858 | * For global direct reclaim, reclaim only the number of pages |
| 1859 | * requested. Less care is taken to scan proportionally as it |
| 1860 | * is more important to minimise direct reclaim stall latency |
| 1861 | * than it is to properly age the LRU lists. |
| 1862 | */ |
| 1863 | if (global_reclaim(sc) && !current_is_kswapd()) |
| 1864 | break; |
| 1865 | |
| 1866 | /* |
| 1867 | * For kswapd and memcg, reclaim at least the number of pages |
| 1868 | * requested. Ensure that the anon and file LRUs shrink |
| 1869 | * proportionally what was requested by get_scan_count(). We |
| 1870 | * stop reclaiming one LRU and reduce the amount scanning |
| 1871 | * proportional to the original scan target. |
| 1872 | */ |
| 1873 | nr_file = nr[LRU_INACTIVE_FILE] + nr[LRU_ACTIVE_FILE]; |
| 1874 | nr_anon = nr[LRU_INACTIVE_ANON] + nr[LRU_ACTIVE_ANON]; |
| 1875 | |
| 1876 | if (nr_file > nr_anon) { |
| 1877 | unsigned long scan_target = targets[LRU_INACTIVE_ANON] + |
| 1878 | targets[LRU_ACTIVE_ANON] + 1; |
| 1879 | lru = LRU_BASE; |
| 1880 | percentage = nr_anon * 100 / scan_target; |
| 1881 | } else { |
| 1882 | unsigned long scan_target = targets[LRU_INACTIVE_FILE] + |
| 1883 | targets[LRU_ACTIVE_FILE] + 1; |
| 1884 | lru = LRU_FILE; |
| 1885 | percentage = nr_file * 100 / scan_target; |
| 1886 | } |
| 1887 | |
| 1888 | /* Stop scanning the smaller of the LRU */ |
| 1889 | nr[lru] = 0; |
| 1890 | nr[lru + LRU_ACTIVE] = 0; |
| 1891 | |
| 1892 | /* |
| 1893 | * Recalculate the other LRU scan count based on its original |
| 1894 | * scan target and the percentage scanning already complete |
| 1895 | */ |
| 1896 | lru = (lru == LRU_FILE) ? LRU_BASE : LRU_FILE; |
| 1897 | nr_scanned = targets[lru] - nr[lru]; |
| 1898 | nr[lru] = targets[lru] * (100 - percentage) / 100; |
| 1899 | nr[lru] -= min(nr[lru], nr_scanned); |
| 1900 | |
| 1901 | lru += LRU_ACTIVE; |
| 1902 | nr_scanned = targets[lru] - nr[lru]; |
| 1903 | nr[lru] = targets[lru] * (100 - percentage) / 100; |
| 1904 | nr[lru] -= min(nr[lru], nr_scanned); |
| 1905 | |
| 1906 | scan_adjusted = true; |
| 1907 | } |
| 1908 | blk_finish_plug(&plug); |
| 1909 | sc->nr_reclaimed += nr_reclaimed; |
| 1910 | |
| 1911 | /* |
| 1912 | * Even if we did not try to evict anon pages at all, we want to |
| 1913 | * rebalance the anon lru active/inactive ratio. |
| 1914 | */ |
| 1915 | if (inactive_anon_is_low(lruvec)) |
| 1916 | shrink_active_list(SWAP_CLUSTER_MAX, lruvec, |
| 1917 | sc, LRU_ACTIVE_ANON); |
| 1918 | |
| 1919 | throttle_vm_writeout(sc->gfp_mask); |
| 1920 | } |
| 1921 | |
| 1922 | /* Use reclaim/compaction for costly allocs or under memory pressure */ |
| 1923 | static bool in_reclaim_compaction(struct scan_control *sc) |
| 1924 | { |
| 1925 | if (IS_ENABLED(CONFIG_COMPACTION) && sc->order && |
| 1926 | (sc->order > PAGE_ALLOC_COSTLY_ORDER || |
| 1927 | sc->priority < DEF_PRIORITY - 2)) |
| 1928 | return true; |
| 1929 | |
| 1930 | return false; |
| 1931 | } |
| 1932 | |
| 1933 | /* |
| 1934 | * Reclaim/compaction is used for high-order allocation requests. It reclaims |
| 1935 | * order-0 pages before compacting the zone. should_continue_reclaim() returns |
| 1936 | * true if more pages should be reclaimed such that when the page allocator |
| 1937 | * calls try_to_compact_zone() that it will have enough free pages to succeed. |
| 1938 | * It will give up earlier than that if there is difficulty reclaiming pages. |
| 1939 | */ |
| 1940 | static inline bool should_continue_reclaim(struct zone *zone, |
| 1941 | unsigned long nr_reclaimed, |
| 1942 | unsigned long nr_scanned, |
| 1943 | struct scan_control *sc) |
| 1944 | { |
| 1945 | unsigned long pages_for_compaction; |
| 1946 | unsigned long inactive_lru_pages; |
| 1947 | |
| 1948 | /* If not in reclaim/compaction mode, stop */ |
| 1949 | if (!in_reclaim_compaction(sc)) |
| 1950 | return false; |
| 1951 | |
| 1952 | /* Consider stopping depending on scan and reclaim activity */ |
| 1953 | if (sc->gfp_mask & __GFP_REPEAT) { |
| 1954 | /* |
| 1955 | * For __GFP_REPEAT allocations, stop reclaiming if the |
| 1956 | * full LRU list has been scanned and we are still failing |
| 1957 | * to reclaim pages. This full LRU scan is potentially |
| 1958 | * expensive but a __GFP_REPEAT caller really wants to succeed |
| 1959 | */ |
| 1960 | if (!nr_reclaimed && !nr_scanned) |
| 1961 | return false; |
| 1962 | } else { |
| 1963 | /* |
| 1964 | * For non-__GFP_REPEAT allocations which can presumably |
| 1965 | * fail without consequence, stop if we failed to reclaim |
| 1966 | * any pages from the last SWAP_CLUSTER_MAX number of |
| 1967 | * pages that were scanned. This will return to the |
| 1968 | * caller faster at the risk reclaim/compaction and |
| 1969 | * the resulting allocation attempt fails |
| 1970 | */ |
| 1971 | if (!nr_reclaimed) |
| 1972 | return false; |
| 1973 | } |
| 1974 | |
| 1975 | /* |
| 1976 | * If we have not reclaimed enough pages for compaction and the |
| 1977 | * inactive lists are large enough, continue reclaiming |
| 1978 | */ |
| 1979 | pages_for_compaction = (2UL << sc->order); |
| 1980 | inactive_lru_pages = zone_page_state(zone, NR_INACTIVE_FILE); |
| 1981 | if (get_nr_swap_pages() > 0) |
| 1982 | inactive_lru_pages += zone_page_state(zone, NR_INACTIVE_ANON); |
| 1983 | if (sc->nr_reclaimed < pages_for_compaction && |
| 1984 | inactive_lru_pages > pages_for_compaction) |
| 1985 | return true; |
| 1986 | |
| 1987 | /* If compaction would go ahead or the allocation would succeed, stop */ |
| 1988 | switch (compaction_suitable(zone, sc->order)) { |
| 1989 | case COMPACT_PARTIAL: |
| 1990 | case COMPACT_CONTINUE: |
| 1991 | return false; |
| 1992 | default: |
| 1993 | return true; |
| 1994 | } |
| 1995 | } |
| 1996 | |
| 1997 | static void shrink_zone(struct zone *zone, struct scan_control *sc) |
| 1998 | { |
| 1999 | unsigned long nr_reclaimed, nr_scanned; |
| 2000 | |
| 2001 | do { |
| 2002 | struct mem_cgroup *root = sc->target_mem_cgroup; |
| 2003 | struct mem_cgroup_reclaim_cookie reclaim = { |
| 2004 | .zone = zone, |
| 2005 | .priority = sc->priority, |
| 2006 | }; |
| 2007 | struct mem_cgroup *memcg; |
| 2008 | |
| 2009 | nr_reclaimed = sc->nr_reclaimed; |
| 2010 | nr_scanned = sc->nr_scanned; |
| 2011 | |
| 2012 | memcg = mem_cgroup_iter(root, NULL, &reclaim); |
| 2013 | do { |
| 2014 | struct lruvec *lruvec; |
| 2015 | |
| 2016 | lruvec = mem_cgroup_zone_lruvec(zone, memcg); |
| 2017 | |
| 2018 | shrink_lruvec(lruvec, sc); |
| 2019 | |
| 2020 | /* |
| 2021 | * Direct reclaim and kswapd have to scan all memory |
| 2022 | * cgroups to fulfill the overall scan target for the |
| 2023 | * zone. |
| 2024 | * |
| 2025 | * Limit reclaim, on the other hand, only cares about |
| 2026 | * nr_to_reclaim pages to be reclaimed and it will |
| 2027 | * retry with decreasing priority if one round over the |
| 2028 | * whole hierarchy is not sufficient. |
| 2029 | */ |
| 2030 | if (!global_reclaim(sc) && |
| 2031 | sc->nr_reclaimed >= sc->nr_to_reclaim) { |
| 2032 | mem_cgroup_iter_break(root, memcg); |
| 2033 | break; |
| 2034 | } |
| 2035 | memcg = mem_cgroup_iter(root, memcg, &reclaim); |
| 2036 | } while (memcg); |
| 2037 | |
| 2038 | vmpressure(sc->gfp_mask, sc->target_mem_cgroup, |
| 2039 | sc->nr_scanned - nr_scanned, |
| 2040 | sc->nr_reclaimed - nr_reclaimed); |
| 2041 | |
| 2042 | } while (should_continue_reclaim(zone, sc->nr_reclaimed - nr_reclaimed, |
| 2043 | sc->nr_scanned - nr_scanned, sc)); |
| 2044 | } |
| 2045 | |
| 2046 | /* Returns true if compaction should go ahead for a high-order request */ |
| 2047 | static inline bool compaction_ready(struct zone *zone, struct scan_control *sc) |
| 2048 | { |
| 2049 | unsigned long balance_gap, watermark; |
| 2050 | bool watermark_ok; |
| 2051 | |
| 2052 | /* Do not consider compaction for orders reclaim is meant to satisfy */ |
| 2053 | if (sc->order <= PAGE_ALLOC_COSTLY_ORDER) |
| 2054 | return false; |
| 2055 | |
| 2056 | /* |
| 2057 | * Compaction takes time to run and there are potentially other |
| 2058 | * callers using the pages just freed. Continue reclaiming until |
| 2059 | * there is a buffer of free pages available to give compaction |
| 2060 | * a reasonable chance of completing and allocating the page |
| 2061 | */ |
| 2062 | balance_gap = min(low_wmark_pages(zone), |
| 2063 | (zone->managed_pages + KSWAPD_ZONE_BALANCE_GAP_RATIO-1) / |
| 2064 | KSWAPD_ZONE_BALANCE_GAP_RATIO); |
| 2065 | watermark = high_wmark_pages(zone) + balance_gap + (2UL << sc->order); |
| 2066 | watermark_ok = zone_watermark_ok_safe(zone, 0, watermark, 0, 0); |
| 2067 | |
| 2068 | /* |
| 2069 | * If compaction is deferred, reclaim up to a point where |
| 2070 | * compaction will have a chance of success when re-enabled |
| 2071 | */ |
| 2072 | if (compaction_deferred(zone, sc->order)) |
| 2073 | return watermark_ok; |
| 2074 | |
| 2075 | /* If compaction is not ready to start, keep reclaiming */ |
| 2076 | if (!compaction_suitable(zone, sc->order)) |
| 2077 | return false; |
| 2078 | |
| 2079 | return watermark_ok; |
| 2080 | } |
| 2081 | |
| 2082 | /* |
| 2083 | * This is the direct reclaim path, for page-allocating processes. We only |
| 2084 | * try to reclaim pages from zones which will satisfy the caller's allocation |
| 2085 | * request. |
| 2086 | * |
| 2087 | * We reclaim from a zone even if that zone is over high_wmark_pages(zone). |
| 2088 | * Because: |
| 2089 | * a) The caller may be trying to free *extra* pages to satisfy a higher-order |
| 2090 | * allocation or |
| 2091 | * b) The target zone may be at high_wmark_pages(zone) but the lower zones |
| 2092 | * must go *over* high_wmark_pages(zone) to satisfy the `incremental min' |
| 2093 | * zone defense algorithm. |
| 2094 | * |
| 2095 | * If a zone is deemed to be full of pinned pages then just give it a light |
| 2096 | * scan then give up on it. |
| 2097 | * |
| 2098 | * This function returns true if a zone is being reclaimed for a costly |
| 2099 | * high-order allocation and compaction is ready to begin. This indicates to |
| 2100 | * the caller that it should consider retrying the allocation instead of |
| 2101 | * further reclaim. |
| 2102 | */ |
| 2103 | static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc) |
| 2104 | { |
| 2105 | struct zoneref *z; |
| 2106 | struct zone *zone; |
| 2107 | unsigned long nr_soft_reclaimed; |
| 2108 | unsigned long nr_soft_scanned; |
| 2109 | bool aborted_reclaim = false; |
| 2110 | |
| 2111 | /* |
| 2112 | * If the number of buffer_heads in the machine exceeds the maximum |
| 2113 | * allowed level, force direct reclaim to scan the highmem zone as |
| 2114 | * highmem pages could be pinning lowmem pages storing buffer_heads |
| 2115 | */ |
| 2116 | if (buffer_heads_over_limit) |
| 2117 | sc->gfp_mask |= __GFP_HIGHMEM; |
| 2118 | |
| 2119 | for_each_zone_zonelist_nodemask(zone, z, zonelist, |
| 2120 | gfp_zone(sc->gfp_mask), sc->nodemask) { |
| 2121 | if (!populated_zone(zone)) |
| 2122 | continue; |
| 2123 | /* |
| 2124 | * Take care memory controller reclaiming has small influence |
| 2125 | * to global LRU. |
| 2126 | */ |
| 2127 | if (global_reclaim(sc)) { |
| 2128 | if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
| 2129 | continue; |
| 2130 | if (zone->all_unreclaimable && |
| 2131 | sc->priority != DEF_PRIORITY) |
| 2132 | continue; /* Let kswapd poll it */ |
| 2133 | if (IS_ENABLED(CONFIG_COMPACTION)) { |
| 2134 | /* |
| 2135 | * If we already have plenty of memory free for |
| 2136 | * compaction in this zone, don't free any more. |
| 2137 | * Even though compaction is invoked for any |
| 2138 | * non-zero order, only frequent costly order |
| 2139 | * reclamation is disruptive enough to become a |
| 2140 | * noticeable problem, like transparent huge |
| 2141 | * page allocations. |
| 2142 | */ |
| 2143 | if (compaction_ready(zone, sc)) { |
| 2144 | aborted_reclaim = true; |
| 2145 | continue; |
| 2146 | } |
| 2147 | } |
| 2148 | /* |
| 2149 | * This steals pages from memory cgroups over softlimit |
| 2150 | * and returns the number of reclaimed pages and |
| 2151 | * scanned pages. This works for global memory pressure |
| 2152 | * and balancing, not for a memcg's limit. |
| 2153 | */ |
| 2154 | nr_soft_scanned = 0; |
| 2155 | nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone, |
| 2156 | sc->order, sc->gfp_mask, |
| 2157 | &nr_soft_scanned); |
| 2158 | sc->nr_reclaimed += nr_soft_reclaimed; |
| 2159 | sc->nr_scanned += nr_soft_scanned; |
| 2160 | /* need some check for avoid more shrink_zone() */ |
| 2161 | } |
| 2162 | |
| 2163 | shrink_zone(zone, sc); |
| 2164 | } |
| 2165 | |
| 2166 | return aborted_reclaim; |
| 2167 | } |
| 2168 | |
| 2169 | static bool zone_reclaimable(struct zone *zone) |
| 2170 | { |
| 2171 | return zone->pages_scanned < zone_reclaimable_pages(zone) * 6; |
| 2172 | } |
| 2173 | |
| 2174 | /* All zones in zonelist are unreclaimable? */ |
| 2175 | static bool all_unreclaimable(struct zonelist *zonelist, |
| 2176 | struct scan_control *sc) |
| 2177 | { |
| 2178 | struct zoneref *z; |
| 2179 | struct zone *zone; |
| 2180 | |
| 2181 | for_each_zone_zonelist_nodemask(zone, z, zonelist, |
| 2182 | gfp_zone(sc->gfp_mask), sc->nodemask) { |
| 2183 | if (!populated_zone(zone)) |
| 2184 | continue; |
| 2185 | if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
| 2186 | continue; |
| 2187 | if (!zone->all_unreclaimable) |
| 2188 | return false; |
| 2189 | } |
| 2190 | |
| 2191 | return true; |
| 2192 | } |
| 2193 | |
| 2194 | /* |
| 2195 | * This is the main entry point to direct page reclaim. |
| 2196 | * |
| 2197 | * If a full scan of the inactive list fails to free enough memory then we |
| 2198 | * are "out of memory" and something needs to be killed. |
| 2199 | * |
| 2200 | * If the caller is !__GFP_FS then the probability of a failure is reasonably |
| 2201 | * high - the zone may be full of dirty or under-writeback pages, which this |
| 2202 | * caller can't do much about. We kick the writeback threads and take explicit |
| 2203 | * naps in the hope that some of these pages can be written. But if the |
| 2204 | * allocating task holds filesystem locks which prevent writeout this might not |
| 2205 | * work, and the allocation attempt will fail. |
| 2206 | * |
| 2207 | * returns: 0, if no pages reclaimed |
| 2208 | * else, the number of pages reclaimed |
| 2209 | */ |
| 2210 | static unsigned long do_try_to_free_pages(struct zonelist *zonelist, |
| 2211 | struct scan_control *sc, |
| 2212 | struct shrink_control *shrink) |
| 2213 | { |
| 2214 | unsigned long total_scanned = 0; |
| 2215 | struct reclaim_state *reclaim_state = current->reclaim_state; |
| 2216 | struct zoneref *z; |
| 2217 | struct zone *zone; |
| 2218 | unsigned long writeback_threshold; |
| 2219 | bool aborted_reclaim; |
| 2220 | |
| 2221 | delayacct_freepages_start(); |
| 2222 | |
| 2223 | if (global_reclaim(sc)) |
| 2224 | count_vm_event(ALLOCSTALL); |
| 2225 | |
| 2226 | do { |
| 2227 | vmpressure_prio(sc->gfp_mask, sc->target_mem_cgroup, |
| 2228 | sc->priority); |
| 2229 | sc->nr_scanned = 0; |
| 2230 | aborted_reclaim = shrink_zones(zonelist, sc); |
| 2231 | |
| 2232 | /* |
| 2233 | * Don't shrink slabs when reclaiming memory from |
| 2234 | * over limit cgroups |
| 2235 | */ |
| 2236 | if (global_reclaim(sc)) { |
| 2237 | unsigned long lru_pages = 0; |
| 2238 | for_each_zone_zonelist(zone, z, zonelist, |
| 2239 | gfp_zone(sc->gfp_mask)) { |
| 2240 | if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
| 2241 | continue; |
| 2242 | |
| 2243 | lru_pages += zone_reclaimable_pages(zone); |
| 2244 | } |
| 2245 | |
| 2246 | shrink_slab(shrink, sc->nr_scanned, lru_pages); |
| 2247 | if (reclaim_state) { |
| 2248 | sc->nr_reclaimed += reclaim_state->reclaimed_slab; |
| 2249 | reclaim_state->reclaimed_slab = 0; |
| 2250 | } |
| 2251 | } |
| 2252 | total_scanned += sc->nr_scanned; |
| 2253 | if (sc->nr_reclaimed >= sc->nr_to_reclaim) |
| 2254 | goto out; |
| 2255 | |
| 2256 | /* |
| 2257 | * If we're getting trouble reclaiming, start doing |
| 2258 | * writepage even in laptop mode. |
| 2259 | */ |
| 2260 | if (sc->priority < DEF_PRIORITY - 2) |
| 2261 | sc->may_writepage = 1; |
| 2262 | |
| 2263 | /* |
| 2264 | * Try to write back as many pages as we just scanned. This |
| 2265 | * tends to cause slow streaming writers to write data to the |
| 2266 | * disk smoothly, at the dirtying rate, which is nice. But |
| 2267 | * that's undesirable in laptop mode, where we *want* lumpy |
| 2268 | * writeout. So in laptop mode, write out the whole world. |
| 2269 | */ |
| 2270 | writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2; |
| 2271 | if (total_scanned > writeback_threshold) { |
| 2272 | wakeup_flusher_threads(laptop_mode ? 0 : total_scanned, |
| 2273 | WB_REASON_TRY_TO_FREE_PAGES); |
| 2274 | sc->may_writepage = 1; |
| 2275 | } |
| 2276 | |
| 2277 | /* Take a nap, wait for some writeback to complete */ |
| 2278 | if (!sc->hibernation_mode && sc->nr_scanned && |
| 2279 | sc->priority < DEF_PRIORITY - 2) { |
| 2280 | struct zone *preferred_zone; |
| 2281 | |
| 2282 | first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask), |
| 2283 | &cpuset_current_mems_allowed, |
| 2284 | &preferred_zone); |
| 2285 | wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10); |
| 2286 | } |
| 2287 | } while (--sc->priority >= 0); |
| 2288 | |
| 2289 | out: |
| 2290 | delayacct_freepages_end(); |
| 2291 | |
| 2292 | if (sc->nr_reclaimed) |
| 2293 | return sc->nr_reclaimed; |
| 2294 | |
| 2295 | /* |
| 2296 | * As hibernation is going on, kswapd is freezed so that it can't mark |
| 2297 | * the zone into all_unreclaimable. Thus bypassing all_unreclaimable |
| 2298 | * check. |
| 2299 | */ |
| 2300 | if (oom_killer_disabled) |
| 2301 | return 0; |
| 2302 | |
| 2303 | /* Aborted reclaim to try compaction? don't OOM, then */ |
| 2304 | if (aborted_reclaim) |
| 2305 | return 1; |
| 2306 | |
| 2307 | /* top priority shrink_zones still had more to do? don't OOM, then */ |
| 2308 | if (global_reclaim(sc) && !all_unreclaimable(zonelist, sc)) |
| 2309 | return 1; |
| 2310 | |
| 2311 | return 0; |
| 2312 | } |
| 2313 | |
| 2314 | static bool pfmemalloc_watermark_ok(pg_data_t *pgdat) |
| 2315 | { |
| 2316 | struct zone *zone; |
| 2317 | unsigned long pfmemalloc_reserve = 0; |
| 2318 | unsigned long free_pages = 0; |
| 2319 | int i; |
| 2320 | bool wmark_ok; |
| 2321 | |
| 2322 | for (i = 0; i <= ZONE_NORMAL; i++) { |
| 2323 | zone = &pgdat->node_zones[i]; |
| 2324 | pfmemalloc_reserve += min_wmark_pages(zone); |
| 2325 | free_pages += zone_page_state(zone, NR_FREE_PAGES); |
| 2326 | } |
| 2327 | |
| 2328 | wmark_ok = free_pages > pfmemalloc_reserve / 2; |
| 2329 | |
| 2330 | /* kswapd must be awake if processes are being throttled */ |
| 2331 | if (!wmark_ok && waitqueue_active(&pgdat->kswapd_wait)) { |
| 2332 | pgdat->classzone_idx = min(pgdat->classzone_idx, |
| 2333 | (enum zone_type)ZONE_NORMAL); |
| 2334 | wake_up_interruptible(&pgdat->kswapd_wait); |
| 2335 | } |
| 2336 | |
| 2337 | return wmark_ok; |
| 2338 | } |
| 2339 | |
| 2340 | /* |
| 2341 | * Throttle direct reclaimers if backing storage is backed by the network |
| 2342 | * and the PFMEMALLOC reserve for the preferred node is getting dangerously |
| 2343 | * depleted. kswapd will continue to make progress and wake the processes |
| 2344 | * when the low watermark is reached. |
| 2345 | * |
| 2346 | * Returns true if a fatal signal was delivered during throttling. If this |
| 2347 | * happens, the page allocator should not consider triggering the OOM killer. |
| 2348 | */ |
| 2349 | static bool throttle_direct_reclaim(gfp_t gfp_mask, struct zonelist *zonelist, |
| 2350 | nodemask_t *nodemask) |
| 2351 | { |
| 2352 | struct zone *zone; |
| 2353 | int high_zoneidx = gfp_zone(gfp_mask); |
| 2354 | pg_data_t *pgdat; |
| 2355 | |
| 2356 | /* |
| 2357 | * Kernel threads should not be throttled as they may be indirectly |
| 2358 | * responsible for cleaning pages necessary for reclaim to make forward |
| 2359 | * progress. kjournald for example may enter direct reclaim while |
| 2360 | * committing a transaction where throttling it could forcing other |
| 2361 | * processes to block on log_wait_commit(). |
| 2362 | */ |
| 2363 | if (current->flags & PF_KTHREAD) |
| 2364 | goto out; |
| 2365 | |
| 2366 | /* |
| 2367 | * If a fatal signal is pending, this process should not throttle. |
| 2368 | * It should return quickly so it can exit and free its memory |
| 2369 | */ |
| 2370 | if (fatal_signal_pending(current)) |
| 2371 | goto out; |
| 2372 | |
| 2373 | /* Check if the pfmemalloc reserves are ok */ |
| 2374 | first_zones_zonelist(zonelist, high_zoneidx, NULL, &zone); |
| 2375 | pgdat = zone->zone_pgdat; |
| 2376 | if (pfmemalloc_watermark_ok(pgdat)) |
| 2377 | goto out; |
| 2378 | |
| 2379 | /* Account for the throttling */ |
| 2380 | count_vm_event(PGSCAN_DIRECT_THROTTLE); |
| 2381 | |
| 2382 | /* |
| 2383 | * If the caller cannot enter the filesystem, it's possible that it |
| 2384 | * is due to the caller holding an FS lock or performing a journal |
| 2385 | * transaction in the case of a filesystem like ext[3|4]. In this case, |
| 2386 | * it is not safe to block on pfmemalloc_wait as kswapd could be |
| 2387 | * blocked waiting on the same lock. Instead, throttle for up to a |
| 2388 | * second before continuing. |
| 2389 | */ |
| 2390 | if (!(gfp_mask & __GFP_FS)) { |
| 2391 | wait_event_interruptible_timeout(pgdat->pfmemalloc_wait, |
| 2392 | pfmemalloc_watermark_ok(pgdat), HZ); |
| 2393 | |
| 2394 | goto check_pending; |
| 2395 | } |
| 2396 | |
| 2397 | /* Throttle until kswapd wakes the process */ |
| 2398 | wait_event_killable(zone->zone_pgdat->pfmemalloc_wait, |
| 2399 | pfmemalloc_watermark_ok(pgdat)); |
| 2400 | |
| 2401 | check_pending: |
| 2402 | if (fatal_signal_pending(current)) |
| 2403 | return true; |
| 2404 | |
| 2405 | out: |
| 2406 | return false; |
| 2407 | } |
| 2408 | |
| 2409 | unsigned long try_to_free_pages(struct zonelist *zonelist, int order, |
| 2410 | gfp_t gfp_mask, nodemask_t *nodemask) |
| 2411 | { |
| 2412 | unsigned long nr_reclaimed; |
| 2413 | struct scan_control sc = { |
| 2414 | .gfp_mask = (gfp_mask = memalloc_noio_flags(gfp_mask)), |
| 2415 | .may_writepage = !laptop_mode, |
| 2416 | .nr_to_reclaim = SWAP_CLUSTER_MAX, |
| 2417 | .may_unmap = 1, |
| 2418 | .may_swap = 1, |
| 2419 | .order = order, |
| 2420 | .priority = DEF_PRIORITY, |
| 2421 | .target_mem_cgroup = NULL, |
| 2422 | .nodemask = nodemask, |
| 2423 | }; |
| 2424 | struct shrink_control shrink = { |
| 2425 | .gfp_mask = sc.gfp_mask, |
| 2426 | }; |
| 2427 | |
| 2428 | /* |
| 2429 | * Do not enter reclaim if fatal signal was delivered while throttled. |
| 2430 | * 1 is returned so that the page allocator does not OOM kill at this |
| 2431 | * point. |
| 2432 | */ |
| 2433 | if (throttle_direct_reclaim(gfp_mask, zonelist, nodemask)) |
| 2434 | return 1; |
| 2435 | |
| 2436 | trace_mm_vmscan_direct_reclaim_begin(order, |
| 2437 | sc.may_writepage, |
| 2438 | gfp_mask); |
| 2439 | |
| 2440 | nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink); |
| 2441 | |
| 2442 | trace_mm_vmscan_direct_reclaim_end(nr_reclaimed); |
| 2443 | |
| 2444 | return nr_reclaimed; |
| 2445 | } |
| 2446 | |
| 2447 | #ifdef CONFIG_MEMCG |
| 2448 | |
| 2449 | unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *memcg, |
| 2450 | gfp_t gfp_mask, bool noswap, |
| 2451 | struct zone *zone, |
| 2452 | unsigned long *nr_scanned) |
| 2453 | { |
| 2454 | struct scan_control sc = { |
| 2455 | .nr_scanned = 0, |
| 2456 | .nr_to_reclaim = SWAP_CLUSTER_MAX, |
| 2457 | .may_writepage = !laptop_mode, |
| 2458 | .may_unmap = 1, |
| 2459 | .may_swap = !noswap, |
| 2460 | .order = 0, |
| 2461 | .priority = 0, |
| 2462 | .target_mem_cgroup = memcg, |
| 2463 | }; |
| 2464 | struct lruvec *lruvec = mem_cgroup_zone_lruvec(zone, memcg); |
| 2465 | |
| 2466 | sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | |
| 2467 | (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); |
| 2468 | |
| 2469 | trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc.order, |
| 2470 | sc.may_writepage, |
| 2471 | sc.gfp_mask); |
| 2472 | |
| 2473 | /* |
| 2474 | * NOTE: Although we can get the priority field, using it |
| 2475 | * here is not a good idea, since it limits the pages we can scan. |
| 2476 | * if we don't reclaim here, the shrink_zone from balance_pgdat |
| 2477 | * will pick up pages from other mem cgroup's as well. We hack |
| 2478 | * the priority and make it zero. |
| 2479 | */ |
| 2480 | shrink_lruvec(lruvec, &sc); |
| 2481 | |
| 2482 | trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed); |
| 2483 | |
| 2484 | *nr_scanned = sc.nr_scanned; |
| 2485 | return sc.nr_reclaimed; |
| 2486 | } |
| 2487 | |
| 2488 | unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *memcg, |
| 2489 | gfp_t gfp_mask, |
| 2490 | bool noswap) |
| 2491 | { |
| 2492 | struct zonelist *zonelist; |
| 2493 | unsigned long nr_reclaimed; |
| 2494 | int nid; |
| 2495 | struct scan_control sc = { |
| 2496 | .may_writepage = !laptop_mode, |
| 2497 | .may_unmap = 1, |
| 2498 | .may_swap = !noswap, |
| 2499 | .nr_to_reclaim = SWAP_CLUSTER_MAX, |
| 2500 | .order = 0, |
| 2501 | .priority = DEF_PRIORITY, |
| 2502 | .target_mem_cgroup = memcg, |
| 2503 | .nodemask = NULL, /* we don't care the placement */ |
| 2504 | .gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | |
| 2505 | (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK), |
| 2506 | }; |
| 2507 | struct shrink_control shrink = { |
| 2508 | .gfp_mask = sc.gfp_mask, |
| 2509 | }; |
| 2510 | |
| 2511 | /* |
| 2512 | * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't |
| 2513 | * take care of from where we get pages. So the node where we start the |
| 2514 | * scan does not need to be the current node. |
| 2515 | */ |
| 2516 | nid = mem_cgroup_select_victim_node(memcg); |
| 2517 | |
| 2518 | zonelist = NODE_DATA(nid)->node_zonelists; |
| 2519 | |
| 2520 | trace_mm_vmscan_memcg_reclaim_begin(0, |
| 2521 | sc.may_writepage, |
| 2522 | sc.gfp_mask); |
| 2523 | |
| 2524 | nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink); |
| 2525 | |
| 2526 | trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed); |
| 2527 | |
| 2528 | return nr_reclaimed; |
| 2529 | } |
| 2530 | #endif |
| 2531 | |
| 2532 | static void age_active_anon(struct zone *zone, struct scan_control *sc) |
| 2533 | { |
| 2534 | struct mem_cgroup *memcg; |
| 2535 | |
| 2536 | if (!total_swap_pages) |
| 2537 | return; |
| 2538 | |
| 2539 | memcg = mem_cgroup_iter(NULL, NULL, NULL); |
| 2540 | do { |
| 2541 | struct lruvec *lruvec = mem_cgroup_zone_lruvec(zone, memcg); |
| 2542 | |
| 2543 | if (inactive_anon_is_low(lruvec)) |
| 2544 | shrink_active_list(SWAP_CLUSTER_MAX, lruvec, |
| 2545 | sc, LRU_ACTIVE_ANON); |
| 2546 | |
| 2547 | memcg = mem_cgroup_iter(NULL, memcg, NULL); |
| 2548 | } while (memcg); |
| 2549 | } |
| 2550 | |
| 2551 | static bool zone_balanced(struct zone *zone, int order, |
| 2552 | unsigned long balance_gap, int classzone_idx) |
| 2553 | { |
| 2554 | if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone) + |
| 2555 | balance_gap, classzone_idx, 0)) |
| 2556 | return false; |
| 2557 | |
| 2558 | if (IS_ENABLED(CONFIG_COMPACTION) && order && |
| 2559 | !compaction_suitable(zone, order)) |
| 2560 | return false; |
| 2561 | |
| 2562 | return true; |
| 2563 | } |
| 2564 | |
| 2565 | /* |
| 2566 | * pgdat_balanced() is used when checking if a node is balanced. |
| 2567 | * |
| 2568 | * For order-0, all zones must be balanced! |
| 2569 | * |
| 2570 | * For high-order allocations only zones that meet watermarks and are in a |
| 2571 | * zone allowed by the callers classzone_idx are added to balanced_pages. The |
| 2572 | * total of balanced pages must be at least 25% of the zones allowed by |
| 2573 | * classzone_idx for the node to be considered balanced. Forcing all zones to |
| 2574 | * be balanced for high orders can cause excessive reclaim when there are |
| 2575 | * imbalanced zones. |
| 2576 | * The choice of 25% is due to |
| 2577 | * o a 16M DMA zone that is balanced will not balance a zone on any |
| 2578 | * reasonable sized machine |
| 2579 | * o On all other machines, the top zone must be at least a reasonable |
| 2580 | * percentage of the middle zones. For example, on 32-bit x86, highmem |
| 2581 | * would need to be at least 256M for it to be balance a whole node. |
| 2582 | * Similarly, on x86-64 the Normal zone would need to be at least 1G |
| 2583 | * to balance a node on its own. These seemed like reasonable ratios. |
| 2584 | */ |
| 2585 | static bool pgdat_balanced(pg_data_t *pgdat, int order, int classzone_idx) |
| 2586 | { |
| 2587 | unsigned long managed_pages = 0; |
| 2588 | unsigned long balanced_pages = 0; |
| 2589 | int i; |
| 2590 | |
| 2591 | /* Check the watermark levels */ |
| 2592 | for (i = 0; i <= classzone_idx; i++) { |
| 2593 | struct zone *zone = pgdat->node_zones + i; |
| 2594 | |
| 2595 | if (!populated_zone(zone)) |
| 2596 | continue; |
| 2597 | |
| 2598 | managed_pages += zone->managed_pages; |
| 2599 | |
| 2600 | /* |
| 2601 | * A special case here: |
| 2602 | * |
| 2603 | * balance_pgdat() skips over all_unreclaimable after |
| 2604 | * DEF_PRIORITY. Effectively, it considers them balanced so |
| 2605 | * they must be considered balanced here as well! |
| 2606 | */ |
| 2607 | if (zone->all_unreclaimable) { |
| 2608 | balanced_pages += zone->managed_pages; |
| 2609 | continue; |
| 2610 | } |
| 2611 | |
| 2612 | if (zone_balanced(zone, order, 0, i)) |
| 2613 | balanced_pages += zone->managed_pages; |
| 2614 | else if (!order) |
| 2615 | return false; |
| 2616 | } |
| 2617 | |
| 2618 | if (order) |
| 2619 | return balanced_pages >= (managed_pages >> 2); |
| 2620 | else |
| 2621 | return true; |
| 2622 | } |
| 2623 | |
| 2624 | /* |
| 2625 | * Prepare kswapd for sleeping. This verifies that there are no processes |
| 2626 | * waiting in throttle_direct_reclaim() and that watermarks have been met. |
| 2627 | * |
| 2628 | * Returns true if kswapd is ready to sleep |
| 2629 | */ |
| 2630 | static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order, long remaining, |
| 2631 | int classzone_idx) |
| 2632 | { |
| 2633 | /* If a direct reclaimer woke kswapd within HZ/10, it's premature */ |
| 2634 | if (remaining) |
| 2635 | return false; |
| 2636 | |
| 2637 | /* |
| 2638 | * There is a potential race between when kswapd checks its watermarks |
| 2639 | * and a process gets throttled. There is also a potential race if |
| 2640 | * processes get throttled, kswapd wakes, a large process exits therby |
| 2641 | * balancing the zones that causes kswapd to miss a wakeup. If kswapd |
| 2642 | * is going to sleep, no process should be sleeping on pfmemalloc_wait |
| 2643 | * so wake them now if necessary. If necessary, processes will wake |
| 2644 | * kswapd and get throttled again |
| 2645 | */ |
| 2646 | if (waitqueue_active(&pgdat->pfmemalloc_wait)) { |
| 2647 | wake_up(&pgdat->pfmemalloc_wait); |
| 2648 | return false; |
| 2649 | } |
| 2650 | |
| 2651 | return pgdat_balanced(pgdat, order, classzone_idx); |
| 2652 | } |
| 2653 | |
| 2654 | /* |
| 2655 | * kswapd shrinks the zone by the number of pages required to reach |
| 2656 | * the high watermark. |
| 2657 | * |
| 2658 | * Returns true if kswapd scanned at least the requested number of pages to |
| 2659 | * reclaim. This is used to determine if the scanning priority needs to be |
| 2660 | * raised. |
| 2661 | */ |
| 2662 | static bool kswapd_shrink_zone(struct zone *zone, |
| 2663 | struct scan_control *sc, |
| 2664 | unsigned long lru_pages) |
| 2665 | { |
| 2666 | unsigned long nr_slab; |
| 2667 | struct reclaim_state *reclaim_state = current->reclaim_state; |
| 2668 | struct shrink_control shrink = { |
| 2669 | .gfp_mask = sc->gfp_mask, |
| 2670 | }; |
| 2671 | |
| 2672 | /* Reclaim above the high watermark. */ |
| 2673 | sc->nr_to_reclaim = max(SWAP_CLUSTER_MAX, high_wmark_pages(zone)); |
| 2674 | shrink_zone(zone, sc); |
| 2675 | |
| 2676 | reclaim_state->reclaimed_slab = 0; |
| 2677 | nr_slab = shrink_slab(&shrink, sc->nr_scanned, lru_pages); |
| 2678 | sc->nr_reclaimed += reclaim_state->reclaimed_slab; |
| 2679 | |
| 2680 | if (nr_slab == 0 && !zone_reclaimable(zone)) |
| 2681 | zone->all_unreclaimable = 1; |
| 2682 | |
| 2683 | return sc->nr_scanned >= sc->nr_to_reclaim; |
| 2684 | } |
| 2685 | |
| 2686 | /* |
| 2687 | * For kswapd, balance_pgdat() will work across all this node's zones until |
| 2688 | * they are all at high_wmark_pages(zone). |
| 2689 | * |
| 2690 | * Returns the final order kswapd was reclaiming at |
| 2691 | * |
| 2692 | * There is special handling here for zones which are full of pinned pages. |
| 2693 | * This can happen if the pages are all mlocked, or if they are all used by |
| 2694 | * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb. |
| 2695 | * What we do is to detect the case where all pages in the zone have been |
| 2696 | * scanned twice and there has been zero successful reclaim. Mark the zone as |
| 2697 | * dead and from now on, only perform a short scan. Basically we're polling |
| 2698 | * the zone for when the problem goes away. |
| 2699 | * |
| 2700 | * kswapd scans the zones in the highmem->normal->dma direction. It skips |
| 2701 | * zones which have free_pages > high_wmark_pages(zone), but once a zone is |
| 2702 | * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the |
| 2703 | * lower zones regardless of the number of free pages in the lower zones. This |
| 2704 | * interoperates with the page allocator fallback scheme to ensure that aging |
| 2705 | * of pages is balanced across the zones. |
| 2706 | */ |
| 2707 | static unsigned long balance_pgdat(pg_data_t *pgdat, int order, |
| 2708 | int *classzone_idx) |
| 2709 | { |
| 2710 | int i; |
| 2711 | int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */ |
| 2712 | unsigned long nr_soft_reclaimed; |
| 2713 | unsigned long nr_soft_scanned; |
| 2714 | struct scan_control sc = { |
| 2715 | .gfp_mask = GFP_KERNEL, |
| 2716 | .priority = DEF_PRIORITY, |
| 2717 | .may_unmap = 1, |
| 2718 | .may_swap = 1, |
| 2719 | .may_writepage = !laptop_mode, |
| 2720 | .order = order, |
| 2721 | .target_mem_cgroup = NULL, |
| 2722 | }; |
| 2723 | count_vm_event(PAGEOUTRUN); |
| 2724 | |
| 2725 | do { |
| 2726 | unsigned long lru_pages = 0; |
| 2727 | bool raise_priority = true; |
| 2728 | |
| 2729 | sc.nr_reclaimed = 0; |
| 2730 | |
| 2731 | /* |
| 2732 | * Scan in the highmem->dma direction for the highest |
| 2733 | * zone which needs scanning |
| 2734 | */ |
| 2735 | for (i = pgdat->nr_zones - 1; i >= 0; i--) { |
| 2736 | struct zone *zone = pgdat->node_zones + i; |
| 2737 | |
| 2738 | if (!populated_zone(zone)) |
| 2739 | continue; |
| 2740 | |
| 2741 | if (zone->all_unreclaimable && |
| 2742 | sc.priority != DEF_PRIORITY) |
| 2743 | continue; |
| 2744 | |
| 2745 | /* |
| 2746 | * Do some background aging of the anon list, to give |
| 2747 | * pages a chance to be referenced before reclaiming. |
| 2748 | */ |
| 2749 | age_active_anon(zone, &sc); |
| 2750 | |
| 2751 | /* |
| 2752 | * If the number of buffer_heads in the machine |
| 2753 | * exceeds the maximum allowed level and this node |
| 2754 | * has a highmem zone, force kswapd to reclaim from |
| 2755 | * it to relieve lowmem pressure. |
| 2756 | */ |
| 2757 | if (buffer_heads_over_limit && is_highmem_idx(i)) { |
| 2758 | end_zone = i; |
| 2759 | break; |
| 2760 | } |
| 2761 | |
| 2762 | if (!zone_balanced(zone, order, 0, 0)) { |
| 2763 | end_zone = i; |
| 2764 | break; |
| 2765 | } else { |
| 2766 | /* If balanced, clear the congested flag */ |
| 2767 | zone_clear_flag(zone, ZONE_CONGESTED); |
| 2768 | } |
| 2769 | } |
| 2770 | |
| 2771 | if (i < 0) |
| 2772 | goto out; |
| 2773 | |
| 2774 | for (i = 0; i <= end_zone; i++) { |
| 2775 | struct zone *zone = pgdat->node_zones + i; |
| 2776 | |
| 2777 | lru_pages += zone_reclaimable_pages(zone); |
| 2778 | } |
| 2779 | |
| 2780 | /* |
| 2781 | * Now scan the zone in the dma->highmem direction, stopping |
| 2782 | * at the last zone which needs scanning. |
| 2783 | * |
| 2784 | * We do this because the page allocator works in the opposite |
| 2785 | * direction. This prevents the page allocator from allocating |
| 2786 | * pages behind kswapd's direction of progress, which would |
| 2787 | * cause too much scanning of the lower zones. |
| 2788 | */ |
| 2789 | for (i = 0; i <= end_zone; i++) { |
| 2790 | struct zone *zone = pgdat->node_zones + i; |
| 2791 | int testorder; |
| 2792 | unsigned long balance_gap; |
| 2793 | |
| 2794 | if (!populated_zone(zone)) |
| 2795 | continue; |
| 2796 | |
| 2797 | if (zone->all_unreclaimable && |
| 2798 | sc.priority != DEF_PRIORITY) |
| 2799 | continue; |
| 2800 | |
| 2801 | sc.nr_scanned = 0; |
| 2802 | |
| 2803 | nr_soft_scanned = 0; |
| 2804 | /* |
| 2805 | * Call soft limit reclaim before calling shrink_zone. |
| 2806 | */ |
| 2807 | nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone, |
| 2808 | order, sc.gfp_mask, |
| 2809 | &nr_soft_scanned); |
| 2810 | sc.nr_reclaimed += nr_soft_reclaimed; |
| 2811 | |
| 2812 | /* |
| 2813 | * We put equal pressure on every zone, unless |
| 2814 | * one zone has way too many pages free |
| 2815 | * already. The "too many pages" is defined |
| 2816 | * as the high wmark plus a "gap" where the |
| 2817 | * gap is either the low watermark or 1% |
| 2818 | * of the zone, whichever is smaller. |
| 2819 | */ |
| 2820 | balance_gap = min(low_wmark_pages(zone), |
| 2821 | (zone->managed_pages + |
| 2822 | KSWAPD_ZONE_BALANCE_GAP_RATIO-1) / |
| 2823 | KSWAPD_ZONE_BALANCE_GAP_RATIO); |
| 2824 | /* |
| 2825 | * Kswapd reclaims only single pages with compaction |
| 2826 | * enabled. Trying too hard to reclaim until contiguous |
| 2827 | * free pages have become available can hurt performance |
| 2828 | * by evicting too much useful data from memory. |
| 2829 | * Do not reclaim more than needed for compaction. |
| 2830 | */ |
| 2831 | testorder = order; |
| 2832 | if (IS_ENABLED(CONFIG_COMPACTION) && order && |
| 2833 | compaction_suitable(zone, order) != |
| 2834 | COMPACT_SKIPPED) |
| 2835 | testorder = 0; |
| 2836 | |
| 2837 | if ((buffer_heads_over_limit && is_highmem_idx(i)) || |
| 2838 | !zone_balanced(zone, testorder, |
| 2839 | balance_gap, end_zone)) { |
| 2840 | /* |
| 2841 | * There should be no need to raise the |
| 2842 | * scanning priority if enough pages are |
| 2843 | * already being scanned that high |
| 2844 | * watermark would be met at 100% efficiency. |
| 2845 | */ |
| 2846 | if (kswapd_shrink_zone(zone, &sc, lru_pages)) |
| 2847 | raise_priority = false; |
| 2848 | } |
| 2849 | |
| 2850 | /* |
| 2851 | * If we're getting trouble reclaiming, start doing |
| 2852 | * writepage even in laptop mode. |
| 2853 | */ |
| 2854 | if (sc.priority < DEF_PRIORITY - 2) |
| 2855 | sc.may_writepage = 1; |
| 2856 | |
| 2857 | if (zone->all_unreclaimable) { |
| 2858 | if (end_zone && end_zone == i) |
| 2859 | end_zone--; |
| 2860 | continue; |
| 2861 | } |
| 2862 | |
| 2863 | if (zone_balanced(zone, testorder, 0, end_zone)) |
| 2864 | /* |
| 2865 | * If a zone reaches its high watermark, |
| 2866 | * consider it to be no longer congested. It's |
| 2867 | * possible there are dirty pages backed by |
| 2868 | * congested BDIs but as pressure is relieved, |
| 2869 | * speculatively avoid congestion waits |
| 2870 | */ |
| 2871 | zone_clear_flag(zone, ZONE_CONGESTED); |
| 2872 | } |
| 2873 | |
| 2874 | /* |
| 2875 | * If the low watermark is met there is no need for processes |
| 2876 | * to be throttled on pfmemalloc_wait as they should not be |
| 2877 | * able to safely make forward progress. Wake them |
| 2878 | */ |
| 2879 | if (waitqueue_active(&pgdat->pfmemalloc_wait) && |
| 2880 | pfmemalloc_watermark_ok(pgdat)) |
| 2881 | wake_up(&pgdat->pfmemalloc_wait); |
| 2882 | |
| 2883 | /* |
| 2884 | * Fragmentation may mean that the system cannot be rebalanced |
| 2885 | * for high-order allocations in all zones. If twice the |
| 2886 | * allocation size has been reclaimed and the zones are still |
| 2887 | * not balanced then recheck the watermarks at order-0 to |
| 2888 | * prevent kswapd reclaiming excessively. Assume that a |
| 2889 | * process requested a high-order can direct reclaim/compact. |
| 2890 | */ |
| 2891 | if (order && sc.nr_reclaimed >= 2UL << order) |
| 2892 | order = sc.order = 0; |
| 2893 | |
| 2894 | /* Check if kswapd should be suspending */ |
| 2895 | if (try_to_freeze() || kthread_should_stop()) |
| 2896 | break; |
| 2897 | |
| 2898 | /* |
| 2899 | * Raise priority if scanning rate is too low or there was no |
| 2900 | * progress in reclaiming pages |
| 2901 | */ |
| 2902 | if (raise_priority || !sc.nr_reclaimed) |
| 2903 | sc.priority--; |
| 2904 | } while (sc.priority >= 0 && |
| 2905 | !pgdat_balanced(pgdat, order, *classzone_idx)); |
| 2906 | |
| 2907 | /* |
| 2908 | * If kswapd was reclaiming at a higher order, it has the option of |
| 2909 | * sleeping without all zones being balanced. Before it does, it must |
| 2910 | * ensure that the watermarks for order-0 on *all* zones are met and |
| 2911 | * that the congestion flags are cleared. The congestion flag must |
| 2912 | * be cleared as kswapd is the only mechanism that clears the flag |
| 2913 | * and it is potentially going to sleep here. |
| 2914 | */ |
| 2915 | if (order) { |
| 2916 | int zones_need_compaction = 1; |
| 2917 | |
| 2918 | for (i = 0; i <= end_zone; i++) { |
| 2919 | struct zone *zone = pgdat->node_zones + i; |
| 2920 | |
| 2921 | if (!populated_zone(zone)) |
| 2922 | continue; |
| 2923 | |
| 2924 | /* Check if the memory needs to be defragmented. */ |
| 2925 | if (zone_watermark_ok(zone, order, |
| 2926 | low_wmark_pages(zone), *classzone_idx, 0)) |
| 2927 | zones_need_compaction = 0; |
| 2928 | } |
| 2929 | |
| 2930 | if (zones_need_compaction) |
| 2931 | compact_pgdat(pgdat, order); |
| 2932 | } |
| 2933 | |
| 2934 | out: |
| 2935 | /* |
| 2936 | * Return the order we were reclaiming at so prepare_kswapd_sleep() |
| 2937 | * makes a decision on the order we were last reclaiming at. However, |
| 2938 | * if another caller entered the allocator slow path while kswapd |
| 2939 | * was awake, order will remain at the higher level |
| 2940 | */ |
| 2941 | *classzone_idx = end_zone; |
| 2942 | return order; |
| 2943 | } |
| 2944 | |
| 2945 | static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx) |
| 2946 | { |
| 2947 | long remaining = 0; |
| 2948 | DEFINE_WAIT(wait); |
| 2949 | |
| 2950 | if (freezing(current) || kthread_should_stop()) |
| 2951 | return; |
| 2952 | |
| 2953 | prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); |
| 2954 | |
| 2955 | /* Try to sleep for a short interval */ |
| 2956 | if (prepare_kswapd_sleep(pgdat, order, remaining, classzone_idx)) { |
| 2957 | remaining = schedule_timeout(HZ/10); |
| 2958 | finish_wait(&pgdat->kswapd_wait, &wait); |
| 2959 | prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); |
| 2960 | } |
| 2961 | |
| 2962 | /* |
| 2963 | * After a short sleep, check if it was a premature sleep. If not, then |
| 2964 | * go fully to sleep until explicitly woken up. |
| 2965 | */ |
| 2966 | if (prepare_kswapd_sleep(pgdat, order, remaining, classzone_idx)) { |
| 2967 | trace_mm_vmscan_kswapd_sleep(pgdat->node_id); |
| 2968 | |
| 2969 | /* |
| 2970 | * vmstat counters are not perfectly accurate and the estimated |
| 2971 | * value for counters such as NR_FREE_PAGES can deviate from the |
| 2972 | * true value by nr_online_cpus * threshold. To avoid the zone |
| 2973 | * watermarks being breached while under pressure, we reduce the |
| 2974 | * per-cpu vmstat threshold while kswapd is awake and restore |
| 2975 | * them before going back to sleep. |
| 2976 | */ |
| 2977 | set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold); |
| 2978 | |
| 2979 | /* |
| 2980 | * Compaction records what page blocks it recently failed to |
| 2981 | * isolate pages from and skips them in the future scanning. |
| 2982 | * When kswapd is going to sleep, it is reasonable to assume |
| 2983 | * that pages and compaction may succeed so reset the cache. |
| 2984 | */ |
| 2985 | reset_isolation_suitable(pgdat); |
| 2986 | |
| 2987 | if (!kthread_should_stop()) |
| 2988 | schedule(); |
| 2989 | |
| 2990 | set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold); |
| 2991 | } else { |
| 2992 | if (remaining) |
| 2993 | count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY); |
| 2994 | else |
| 2995 | count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY); |
| 2996 | } |
| 2997 | finish_wait(&pgdat->kswapd_wait, &wait); |
| 2998 | } |
| 2999 | |
| 3000 | /* |
| 3001 | * The background pageout daemon, started as a kernel thread |
| 3002 | * from the init process. |
| 3003 | * |
| 3004 | * This basically trickles out pages so that we have _some_ |
| 3005 | * free memory available even if there is no other activity |
| 3006 | * that frees anything up. This is needed for things like routing |
| 3007 | * etc, where we otherwise might have all activity going on in |
| 3008 | * asynchronous contexts that cannot page things out. |
| 3009 | * |
| 3010 | * If there are applications that are active memory-allocators |
| 3011 | * (most normal use), this basically shouldn't matter. |
| 3012 | */ |
| 3013 | static int kswapd(void *p) |
| 3014 | { |
| 3015 | unsigned long order, new_order; |
| 3016 | unsigned balanced_order; |
| 3017 | int classzone_idx, new_classzone_idx; |
| 3018 | int balanced_classzone_idx; |
| 3019 | pg_data_t *pgdat = (pg_data_t*)p; |
| 3020 | struct task_struct *tsk = current; |
| 3021 | |
| 3022 | struct reclaim_state reclaim_state = { |
| 3023 | .reclaimed_slab = 0, |
| 3024 | }; |
| 3025 | const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id); |
| 3026 | |
| 3027 | lockdep_set_current_reclaim_state(GFP_KERNEL); |
| 3028 | |
| 3029 | if (!cpumask_empty(cpumask)) |
| 3030 | set_cpus_allowed_ptr(tsk, cpumask); |
| 3031 | current->reclaim_state = &reclaim_state; |
| 3032 | |
| 3033 | /* |
| 3034 | * Tell the memory management that we're a "memory allocator", |
| 3035 | * and that if we need more memory we should get access to it |
| 3036 | * regardless (see "__alloc_pages()"). "kswapd" should |
| 3037 | * never get caught in the normal page freeing logic. |
| 3038 | * |
| 3039 | * (Kswapd normally doesn't need memory anyway, but sometimes |
| 3040 | * you need a small amount of memory in order to be able to |
| 3041 | * page out something else, and this flag essentially protects |
| 3042 | * us from recursively trying to free more memory as we're |
| 3043 | * trying to free the first piece of memory in the first place). |
| 3044 | */ |
| 3045 | tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD; |
| 3046 | set_freezable(); |
| 3047 | |
| 3048 | order = new_order = 0; |
| 3049 | balanced_order = 0; |
| 3050 | classzone_idx = new_classzone_idx = pgdat->nr_zones - 1; |
| 3051 | balanced_classzone_idx = classzone_idx; |
| 3052 | for ( ; ; ) { |
| 3053 | bool ret; |
| 3054 | |
| 3055 | /* |
| 3056 | * If the last balance_pgdat was unsuccessful it's unlikely a |
| 3057 | * new request of a similar or harder type will succeed soon |
| 3058 | * so consider going to sleep on the basis we reclaimed at |
| 3059 | */ |
| 3060 | if (balanced_classzone_idx >= new_classzone_idx && |
| 3061 | balanced_order == new_order) { |
| 3062 | new_order = pgdat->kswapd_max_order; |
| 3063 | new_classzone_idx = pgdat->classzone_idx; |
| 3064 | pgdat->kswapd_max_order = 0; |
| 3065 | pgdat->classzone_idx = pgdat->nr_zones - 1; |
| 3066 | } |
| 3067 | |
| 3068 | if (order < new_order || classzone_idx > new_classzone_idx) { |
| 3069 | /* |
| 3070 | * Don't sleep if someone wants a larger 'order' |
| 3071 | * allocation or has tigher zone constraints |
| 3072 | */ |
| 3073 | order = new_order; |
| 3074 | classzone_idx = new_classzone_idx; |
| 3075 | } else { |
| 3076 | kswapd_try_to_sleep(pgdat, balanced_order, |
| 3077 | balanced_classzone_idx); |
| 3078 | order = pgdat->kswapd_max_order; |
| 3079 | classzone_idx = pgdat->classzone_idx; |
| 3080 | new_order = order; |
| 3081 | new_classzone_idx = classzone_idx; |
| 3082 | pgdat->kswapd_max_order = 0; |
| 3083 | pgdat->classzone_idx = pgdat->nr_zones - 1; |
| 3084 | } |
| 3085 | |
| 3086 | ret = try_to_freeze(); |
| 3087 | if (kthread_should_stop()) |
| 3088 | break; |
| 3089 | |
| 3090 | /* |
| 3091 | * We can speed up thawing tasks if we don't call balance_pgdat |
| 3092 | * after returning from the refrigerator |
| 3093 | */ |
| 3094 | if (!ret) { |
| 3095 | trace_mm_vmscan_kswapd_wake(pgdat->node_id, order); |
| 3096 | balanced_classzone_idx = classzone_idx; |
| 3097 | balanced_order = balance_pgdat(pgdat, order, |
| 3098 | &balanced_classzone_idx); |
| 3099 | } |
| 3100 | } |
| 3101 | |
| 3102 | current->reclaim_state = NULL; |
| 3103 | return 0; |
| 3104 | } |
| 3105 | |
| 3106 | /* |
| 3107 | * A zone is low on free memory, so wake its kswapd task to service it. |
| 3108 | */ |
| 3109 | void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx) |
| 3110 | { |
| 3111 | pg_data_t *pgdat; |
| 3112 | |
| 3113 | if (!populated_zone(zone)) |
| 3114 | return; |
| 3115 | |
| 3116 | if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
| 3117 | return; |
| 3118 | pgdat = zone->zone_pgdat; |
| 3119 | if (pgdat->kswapd_max_order < order) { |
| 3120 | pgdat->kswapd_max_order = order; |
| 3121 | pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx); |
| 3122 | } |
| 3123 | if (!waitqueue_active(&pgdat->kswapd_wait)) |
| 3124 | return; |
| 3125 | if (zone_watermark_ok_safe(zone, order, low_wmark_pages(zone), 0, 0)) |
| 3126 | return; |
| 3127 | |
| 3128 | trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order); |
| 3129 | wake_up_interruptible(&pgdat->kswapd_wait); |
| 3130 | } |
| 3131 | |
| 3132 | /* |
| 3133 | * The reclaimable count would be mostly accurate. |
| 3134 | * The less reclaimable pages may be |
| 3135 | * - mlocked pages, which will be moved to unevictable list when encountered |
| 3136 | * - mapped pages, which may require several travels to be reclaimed |
| 3137 | * - dirty pages, which is not "instantly" reclaimable |
| 3138 | */ |
| 3139 | unsigned long global_reclaimable_pages(void) |
| 3140 | { |
| 3141 | int nr; |
| 3142 | |
| 3143 | nr = global_page_state(NR_ACTIVE_FILE) + |
| 3144 | global_page_state(NR_INACTIVE_FILE); |
| 3145 | |
| 3146 | if (get_nr_swap_pages() > 0) |
| 3147 | nr += global_page_state(NR_ACTIVE_ANON) + |
| 3148 | global_page_state(NR_INACTIVE_ANON); |
| 3149 | |
| 3150 | return nr; |
| 3151 | } |
| 3152 | |
| 3153 | unsigned long zone_reclaimable_pages(struct zone *zone) |
| 3154 | { |
| 3155 | int nr; |
| 3156 | |
| 3157 | nr = zone_page_state(zone, NR_ACTIVE_FILE) + |
| 3158 | zone_page_state(zone, NR_INACTIVE_FILE); |
| 3159 | |
| 3160 | if (get_nr_swap_pages() > 0) |
| 3161 | nr += zone_page_state(zone, NR_ACTIVE_ANON) + |
| 3162 | zone_page_state(zone, NR_INACTIVE_ANON); |
| 3163 | |
| 3164 | return nr; |
| 3165 | } |
| 3166 | |
| 3167 | #ifdef CONFIG_HIBERNATION |
| 3168 | /* |
| 3169 | * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of |
| 3170 | * freed pages. |
| 3171 | * |
| 3172 | * Rather than trying to age LRUs the aim is to preserve the overall |
| 3173 | * LRU order by reclaiming preferentially |
| 3174 | * inactive > active > active referenced > active mapped |
| 3175 | */ |
| 3176 | unsigned long shrink_all_memory(unsigned long nr_to_reclaim) |
| 3177 | { |
| 3178 | struct reclaim_state reclaim_state; |
| 3179 | struct scan_control sc = { |
| 3180 | .gfp_mask = GFP_HIGHUSER_MOVABLE, |
| 3181 | .may_swap = 1, |
| 3182 | .may_unmap = 1, |
| 3183 | .may_writepage = 1, |
| 3184 | .nr_to_reclaim = nr_to_reclaim, |
| 3185 | .hibernation_mode = 1, |
| 3186 | .order = 0, |
| 3187 | .priority = DEF_PRIORITY, |
| 3188 | }; |
| 3189 | struct shrink_control shrink = { |
| 3190 | .gfp_mask = sc.gfp_mask, |
| 3191 | }; |
| 3192 | struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask); |
| 3193 | struct task_struct *p = current; |
| 3194 | unsigned long nr_reclaimed; |
| 3195 | |
| 3196 | p->flags |= PF_MEMALLOC; |
| 3197 | lockdep_set_current_reclaim_state(sc.gfp_mask); |
| 3198 | reclaim_state.reclaimed_slab = 0; |
| 3199 | p->reclaim_state = &reclaim_state; |
| 3200 | |
| 3201 | nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink); |
| 3202 | |
| 3203 | p->reclaim_state = NULL; |
| 3204 | lockdep_clear_current_reclaim_state(); |
| 3205 | p->flags &= ~PF_MEMALLOC; |
| 3206 | |
| 3207 | return nr_reclaimed; |
| 3208 | } |
| 3209 | #endif /* CONFIG_HIBERNATION */ |
| 3210 | |
| 3211 | /* It's optimal to keep kswapds on the same CPUs as their memory, but |
| 3212 | not required for correctness. So if the last cpu in a node goes |
| 3213 | away, we get changed to run anywhere: as the first one comes back, |
| 3214 | restore their cpu bindings. */ |
| 3215 | static int cpu_callback(struct notifier_block *nfb, unsigned long action, |
| 3216 | void *hcpu) |
| 3217 | { |
| 3218 | int nid; |
| 3219 | |
| 3220 | if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) { |
| 3221 | for_each_node_state(nid, N_MEMORY) { |
| 3222 | pg_data_t *pgdat = NODE_DATA(nid); |
| 3223 | const struct cpumask *mask; |
| 3224 | |
| 3225 | mask = cpumask_of_node(pgdat->node_id); |
| 3226 | |
| 3227 | if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids) |
| 3228 | /* One of our CPUs online: restore mask */ |
| 3229 | set_cpus_allowed_ptr(pgdat->kswapd, mask); |
| 3230 | } |
| 3231 | } |
| 3232 | return NOTIFY_OK; |
| 3233 | } |
| 3234 | |
| 3235 | /* |
| 3236 | * This kswapd start function will be called by init and node-hot-add. |
| 3237 | * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added. |
| 3238 | */ |
| 3239 | int kswapd_run(int nid) |
| 3240 | { |
| 3241 | pg_data_t *pgdat = NODE_DATA(nid); |
| 3242 | int ret = 0; |
| 3243 | |
| 3244 | if (pgdat->kswapd) |
| 3245 | return 0; |
| 3246 | |
| 3247 | pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid); |
| 3248 | if (IS_ERR(pgdat->kswapd)) { |
| 3249 | /* failure at boot is fatal */ |
| 3250 | BUG_ON(system_state == SYSTEM_BOOTING); |
| 3251 | pr_err("Failed to start kswapd on node %d\n", nid); |
| 3252 | ret = PTR_ERR(pgdat->kswapd); |
| 3253 | pgdat->kswapd = NULL; |
| 3254 | } |
| 3255 | return ret; |
| 3256 | } |
| 3257 | |
| 3258 | /* |
| 3259 | * Called by memory hotplug when all memory in a node is offlined. Caller must |
| 3260 | * hold lock_memory_hotplug(). |
| 3261 | */ |
| 3262 | void kswapd_stop(int nid) |
| 3263 | { |
| 3264 | struct task_struct *kswapd = NODE_DATA(nid)->kswapd; |
| 3265 | |
| 3266 | if (kswapd) { |
| 3267 | kthread_stop(kswapd); |
| 3268 | NODE_DATA(nid)->kswapd = NULL; |
| 3269 | } |
| 3270 | } |
| 3271 | |
| 3272 | static int __init kswapd_init(void) |
| 3273 | { |
| 3274 | int nid; |
| 3275 | |
| 3276 | swap_setup(); |
| 3277 | for_each_node_state(nid, N_MEMORY) |
| 3278 | kswapd_run(nid); |
| 3279 | hotcpu_notifier(cpu_callback, 0); |
| 3280 | return 0; |
| 3281 | } |
| 3282 | |
| 3283 | module_init(kswapd_init) |
| 3284 | |
| 3285 | #ifdef CONFIG_NUMA |
| 3286 | /* |
| 3287 | * Zone reclaim mode |
| 3288 | * |
| 3289 | * If non-zero call zone_reclaim when the number of free pages falls below |
| 3290 | * the watermarks. |
| 3291 | */ |
| 3292 | int zone_reclaim_mode __read_mostly; |
| 3293 | |
| 3294 | #define RECLAIM_OFF 0 |
| 3295 | #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */ |
| 3296 | #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */ |
| 3297 | #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */ |
| 3298 | |
| 3299 | /* |
| 3300 | * Priority for ZONE_RECLAIM. This determines the fraction of pages |
| 3301 | * of a node considered for each zone_reclaim. 4 scans 1/16th of |
| 3302 | * a zone. |
| 3303 | */ |
| 3304 | #define ZONE_RECLAIM_PRIORITY 4 |
| 3305 | |
| 3306 | /* |
| 3307 | * Percentage of pages in a zone that must be unmapped for zone_reclaim to |
| 3308 | * occur. |
| 3309 | */ |
| 3310 | int sysctl_min_unmapped_ratio = 1; |
| 3311 | |
| 3312 | /* |
| 3313 | * If the number of slab pages in a zone grows beyond this percentage then |
| 3314 | * slab reclaim needs to occur. |
| 3315 | */ |
| 3316 | int sysctl_min_slab_ratio = 5; |
| 3317 | |
| 3318 | static inline unsigned long zone_unmapped_file_pages(struct zone *zone) |
| 3319 | { |
| 3320 | unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED); |
| 3321 | unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) + |
| 3322 | zone_page_state(zone, NR_ACTIVE_FILE); |
| 3323 | |
| 3324 | /* |
| 3325 | * It's possible for there to be more file mapped pages than |
| 3326 | * accounted for by the pages on the file LRU lists because |
| 3327 | * tmpfs pages accounted for as ANON can also be FILE_MAPPED |
| 3328 | */ |
| 3329 | return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0; |
| 3330 | } |
| 3331 | |
| 3332 | /* Work out how many page cache pages we can reclaim in this reclaim_mode */ |
| 3333 | static long zone_pagecache_reclaimable(struct zone *zone) |
| 3334 | { |
| 3335 | long nr_pagecache_reclaimable; |
| 3336 | long delta = 0; |
| 3337 | |
| 3338 | /* |
| 3339 | * If RECLAIM_SWAP is set, then all file pages are considered |
| 3340 | * potentially reclaimable. Otherwise, we have to worry about |
| 3341 | * pages like swapcache and zone_unmapped_file_pages() provides |
| 3342 | * a better estimate |
| 3343 | */ |
| 3344 | if (zone_reclaim_mode & RECLAIM_SWAP) |
| 3345 | nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES); |
| 3346 | else |
| 3347 | nr_pagecache_reclaimable = zone_unmapped_file_pages(zone); |
| 3348 | |
| 3349 | /* If we can't clean pages, remove dirty pages from consideration */ |
| 3350 | if (!(zone_reclaim_mode & RECLAIM_WRITE)) |
| 3351 | delta += zone_page_state(zone, NR_FILE_DIRTY); |
| 3352 | |
| 3353 | /* Watch for any possible underflows due to delta */ |
| 3354 | if (unlikely(delta > nr_pagecache_reclaimable)) |
| 3355 | delta = nr_pagecache_reclaimable; |
| 3356 | |
| 3357 | return nr_pagecache_reclaimable - delta; |
| 3358 | } |
| 3359 | |
| 3360 | /* |
| 3361 | * Try to free up some pages from this zone through reclaim. |
| 3362 | */ |
| 3363 | static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) |
| 3364 | { |
| 3365 | /* Minimum pages needed in order to stay on node */ |
| 3366 | const unsigned long nr_pages = 1 << order; |
| 3367 | struct task_struct *p = current; |
| 3368 | struct reclaim_state reclaim_state; |
| 3369 | struct scan_control sc = { |
| 3370 | .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE), |
| 3371 | .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP), |
| 3372 | .may_swap = 1, |
| 3373 | .nr_to_reclaim = max(nr_pages, SWAP_CLUSTER_MAX), |
| 3374 | .gfp_mask = (gfp_mask = memalloc_noio_flags(gfp_mask)), |
| 3375 | .order = order, |
| 3376 | .priority = ZONE_RECLAIM_PRIORITY, |
| 3377 | }; |
| 3378 | struct shrink_control shrink = { |
| 3379 | .gfp_mask = sc.gfp_mask, |
| 3380 | }; |
| 3381 | unsigned long nr_slab_pages0, nr_slab_pages1; |
| 3382 | |
| 3383 | cond_resched(); |
| 3384 | /* |
| 3385 | * We need to be able to allocate from the reserves for RECLAIM_SWAP |
| 3386 | * and we also need to be able to write out pages for RECLAIM_WRITE |
| 3387 | * and RECLAIM_SWAP. |
| 3388 | */ |
| 3389 | p->flags |= PF_MEMALLOC | PF_SWAPWRITE; |
| 3390 | lockdep_set_current_reclaim_state(gfp_mask); |
| 3391 | reclaim_state.reclaimed_slab = 0; |
| 3392 | p->reclaim_state = &reclaim_state; |
| 3393 | |
| 3394 | if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) { |
| 3395 | /* |
| 3396 | * Free memory by calling shrink zone with increasing |
| 3397 | * priorities until we have enough memory freed. |
| 3398 | */ |
| 3399 | do { |
| 3400 | shrink_zone(zone, &sc); |
| 3401 | } while (sc.nr_reclaimed < nr_pages && --sc.priority >= 0); |
| 3402 | } |
| 3403 | |
| 3404 | nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE); |
| 3405 | if (nr_slab_pages0 > zone->min_slab_pages) { |
| 3406 | /* |
| 3407 | * shrink_slab() does not currently allow us to determine how |
| 3408 | * many pages were freed in this zone. So we take the current |
| 3409 | * number of slab pages and shake the slab until it is reduced |
| 3410 | * by the same nr_pages that we used for reclaiming unmapped |
| 3411 | * pages. |
| 3412 | * |
| 3413 | * Note that shrink_slab will free memory on all zones and may |
| 3414 | * take a long time. |
| 3415 | */ |
| 3416 | for (;;) { |
| 3417 | unsigned long lru_pages = zone_reclaimable_pages(zone); |
| 3418 | |
| 3419 | /* No reclaimable slab or very low memory pressure */ |
| 3420 | if (!shrink_slab(&shrink, sc.nr_scanned, lru_pages)) |
| 3421 | break; |
| 3422 | |
| 3423 | /* Freed enough memory */ |
| 3424 | nr_slab_pages1 = zone_page_state(zone, |
| 3425 | NR_SLAB_RECLAIMABLE); |
| 3426 | if (nr_slab_pages1 + nr_pages <= nr_slab_pages0) |
| 3427 | break; |
| 3428 | } |
| 3429 | |
| 3430 | /* |
| 3431 | * Update nr_reclaimed by the number of slab pages we |
| 3432 | * reclaimed from this zone. |
| 3433 | */ |
| 3434 | nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE); |
| 3435 | if (nr_slab_pages1 < nr_slab_pages0) |
| 3436 | sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1; |
| 3437 | } |
| 3438 | |
| 3439 | p->reclaim_state = NULL; |
| 3440 | current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE); |
| 3441 | lockdep_clear_current_reclaim_state(); |
| 3442 | return sc.nr_reclaimed >= nr_pages; |
| 3443 | } |
| 3444 | |
| 3445 | int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) |
| 3446 | { |
| 3447 | int node_id; |
| 3448 | int ret; |
| 3449 | |
| 3450 | /* |
| 3451 | * Zone reclaim reclaims unmapped file backed pages and |
| 3452 | * slab pages if we are over the defined limits. |
| 3453 | * |
| 3454 | * A small portion of unmapped file backed pages is needed for |
| 3455 | * file I/O otherwise pages read by file I/O will be immediately |
| 3456 | * thrown out if the zone is overallocated. So we do not reclaim |
| 3457 | * if less than a specified percentage of the zone is used by |
| 3458 | * unmapped file backed pages. |
| 3459 | */ |
| 3460 | if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages && |
| 3461 | zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages) |
| 3462 | return ZONE_RECLAIM_FULL; |
| 3463 | |
| 3464 | if (zone->all_unreclaimable) |
| 3465 | return ZONE_RECLAIM_FULL; |
| 3466 | |
| 3467 | /* |
| 3468 | * Do not scan if the allocation should not be delayed. |
| 3469 | */ |
| 3470 | if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC)) |
| 3471 | return ZONE_RECLAIM_NOSCAN; |
| 3472 | |
| 3473 | /* |
| 3474 | * Only run zone reclaim on the local zone or on zones that do not |
| 3475 | * have associated processors. This will favor the local processor |
| 3476 | * over remote processors and spread off node memory allocations |
| 3477 | * as wide as possible. |
| 3478 | */ |
| 3479 | node_id = zone_to_nid(zone); |
| 3480 | if (node_state(node_id, N_CPU) && node_id != numa_node_id()) |
| 3481 | return ZONE_RECLAIM_NOSCAN; |
| 3482 | |
| 3483 | if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED)) |
| 3484 | return ZONE_RECLAIM_NOSCAN; |
| 3485 | |
| 3486 | ret = __zone_reclaim(zone, gfp_mask, order); |
| 3487 | zone_clear_flag(zone, ZONE_RECLAIM_LOCKED); |
| 3488 | |
| 3489 | if (!ret) |
| 3490 | count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED); |
| 3491 | |
| 3492 | return ret; |
| 3493 | } |
| 3494 | #endif |
| 3495 | |
| 3496 | /* |
| 3497 | * page_evictable - test whether a page is evictable |
| 3498 | * @page: the page to test |
| 3499 | * |
| 3500 | * Test whether page is evictable--i.e., should be placed on active/inactive |
| 3501 | * lists vs unevictable list. |
| 3502 | * |
| 3503 | * Reasons page might not be evictable: |
| 3504 | * (1) page's mapping marked unevictable |
| 3505 | * (2) page is part of an mlocked VMA |
| 3506 | * |
| 3507 | */ |
| 3508 | int page_evictable(struct page *page) |
| 3509 | { |
| 3510 | return !mapping_unevictable(page_mapping(page)) && !PageMlocked(page); |
| 3511 | } |
| 3512 | |
| 3513 | #ifdef CONFIG_SHMEM |
| 3514 | /** |
| 3515 | * check_move_unevictable_pages - check pages for evictability and move to appropriate zone lru list |
| 3516 | * @pages: array of pages to check |
| 3517 | * @nr_pages: number of pages to check |
| 3518 | * |
| 3519 | * Checks pages for evictability and moves them to the appropriate lru list. |
| 3520 | * |
| 3521 | * This function is only used for SysV IPC SHM_UNLOCK. |
| 3522 | */ |
| 3523 | void check_move_unevictable_pages(struct page **pages, int nr_pages) |
| 3524 | { |
| 3525 | struct lruvec *lruvec; |
| 3526 | struct zone *zone = NULL; |
| 3527 | int pgscanned = 0; |
| 3528 | int pgrescued = 0; |
| 3529 | int i; |
| 3530 | |
| 3531 | for (i = 0; i < nr_pages; i++) { |
| 3532 | struct page *page = pages[i]; |
| 3533 | struct zone *pagezone; |
| 3534 | |
| 3535 | pgscanned++; |
| 3536 | pagezone = page_zone(page); |
| 3537 | if (pagezone != zone) { |
| 3538 | if (zone) |
| 3539 | spin_unlock_irq(&zone->lru_lock); |
| 3540 | zone = pagezone; |
| 3541 | spin_lock_irq(&zone->lru_lock); |
| 3542 | } |
| 3543 | lruvec = mem_cgroup_page_lruvec(page, zone); |
| 3544 | |
| 3545 | if (!PageLRU(page) || !PageUnevictable(page)) |
| 3546 | continue; |
| 3547 | |
| 3548 | if (page_evictable(page)) { |
| 3549 | enum lru_list lru = page_lru_base_type(page); |
| 3550 | |
| 3551 | VM_BUG_ON(PageActive(page)); |
| 3552 | ClearPageUnevictable(page); |
| 3553 | del_page_from_lru_list(page, lruvec, LRU_UNEVICTABLE); |
| 3554 | add_page_to_lru_list(page, lruvec, lru); |
| 3555 | pgrescued++; |
| 3556 | } |
| 3557 | } |
| 3558 | |
| 3559 | if (zone) { |
| 3560 | __count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued); |
| 3561 | __count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned); |
| 3562 | spin_unlock_irq(&zone->lru_lock); |
| 3563 | } |
| 3564 | } |
| 3565 | #endif /* CONFIG_SHMEM */ |
| 3566 | |
| 3567 | static void warn_scan_unevictable_pages(void) |
| 3568 | { |
| 3569 | printk_once(KERN_WARNING |
| 3570 | "%s: The scan_unevictable_pages sysctl/node-interface has been " |
| 3571 | "disabled for lack of a legitimate use case. If you have " |
| 3572 | "one, please send an email to linux-mm@kvack.org.\n", |
| 3573 | current->comm); |
| 3574 | } |
| 3575 | |
| 3576 | /* |
| 3577 | * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of |
| 3578 | * all nodes' unevictable lists for evictable pages |
| 3579 | */ |
| 3580 | unsigned long scan_unevictable_pages; |
| 3581 | |
| 3582 | int scan_unevictable_handler(struct ctl_table *table, int write, |
| 3583 | void __user *buffer, |
| 3584 | size_t *length, loff_t *ppos) |
| 3585 | { |
| 3586 | warn_scan_unevictable_pages(); |
| 3587 | proc_doulongvec_minmax(table, write, buffer, length, ppos); |
| 3588 | scan_unevictable_pages = 0; |
| 3589 | return 0; |
| 3590 | } |
| 3591 | |
| 3592 | #ifdef CONFIG_NUMA |
| 3593 | /* |
| 3594 | * per node 'scan_unevictable_pages' attribute. On demand re-scan of |
| 3595 | * a specified node's per zone unevictable lists for evictable pages. |
| 3596 | */ |
| 3597 | |
| 3598 | static ssize_t read_scan_unevictable_node(struct device *dev, |
| 3599 | struct device_attribute *attr, |
| 3600 | char *buf) |
| 3601 | { |
| 3602 | warn_scan_unevictable_pages(); |
| 3603 | return sprintf(buf, "0\n"); /* always zero; should fit... */ |
| 3604 | } |
| 3605 | |
| 3606 | static ssize_t write_scan_unevictable_node(struct device *dev, |
| 3607 | struct device_attribute *attr, |
| 3608 | const char *buf, size_t count) |
| 3609 | { |
| 3610 | warn_scan_unevictable_pages(); |
| 3611 | return 1; |
| 3612 | } |
| 3613 | |
| 3614 | |
| 3615 | static DEVICE_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR, |
| 3616 | read_scan_unevictable_node, |
| 3617 | write_scan_unevictable_node); |
| 3618 | |
| 3619 | int scan_unevictable_register_node(struct node *node) |
| 3620 | { |
| 3621 | return device_create_file(&node->dev, &dev_attr_scan_unevictable_pages); |
| 3622 | } |
| 3623 | |
| 3624 | void scan_unevictable_unregister_node(struct node *node) |
| 3625 | { |
| 3626 | device_remove_file(&node->dev, &dev_attr_scan_unevictable_pages); |
| 3627 | } |
| 3628 | #endif |