| 1 | /* |
| 2 | * linux/mm/compaction.c |
| 3 | * |
| 4 | * Memory compaction for the reduction of external fragmentation. Note that |
| 5 | * this heavily depends upon page migration to do all the real heavy |
| 6 | * lifting |
| 7 | * |
| 8 | * Copyright IBM Corp. 2007-2010 Mel Gorman <mel@csn.ul.ie> |
| 9 | */ |
| 10 | #include <linux/cpu.h> |
| 11 | #include <linux/swap.h> |
| 12 | #include <linux/migrate.h> |
| 13 | #include <linux/compaction.h> |
| 14 | #include <linux/mm_inline.h> |
| 15 | #include <linux/backing-dev.h> |
| 16 | #include <linux/sysctl.h> |
| 17 | #include <linux/sysfs.h> |
| 18 | #include <linux/balloon_compaction.h> |
| 19 | #include <linux/page-isolation.h> |
| 20 | #include <linux/kasan.h> |
| 21 | #include <linux/kthread.h> |
| 22 | #include <linux/freezer.h> |
| 23 | #include "internal.h" |
| 24 | |
| 25 | #ifdef CONFIG_COMPACTION |
| 26 | static inline void count_compact_event(enum vm_event_item item) |
| 27 | { |
| 28 | count_vm_event(item); |
| 29 | } |
| 30 | |
| 31 | static inline void count_compact_events(enum vm_event_item item, long delta) |
| 32 | { |
| 33 | count_vm_events(item, delta); |
| 34 | } |
| 35 | #else |
| 36 | #define count_compact_event(item) do { } while (0) |
| 37 | #define count_compact_events(item, delta) do { } while (0) |
| 38 | #endif |
| 39 | |
| 40 | #if defined CONFIG_COMPACTION || defined CONFIG_CMA |
| 41 | |
| 42 | #define CREATE_TRACE_POINTS |
| 43 | #include <trace/events/compaction.h> |
| 44 | |
| 45 | static unsigned long release_freepages(struct list_head *freelist) |
| 46 | { |
| 47 | struct page *page, *next; |
| 48 | unsigned long high_pfn = 0; |
| 49 | |
| 50 | list_for_each_entry_safe(page, next, freelist, lru) { |
| 51 | unsigned long pfn = page_to_pfn(page); |
| 52 | list_del(&page->lru); |
| 53 | __free_page(page); |
| 54 | if (pfn > high_pfn) |
| 55 | high_pfn = pfn; |
| 56 | } |
| 57 | |
| 58 | return high_pfn; |
| 59 | } |
| 60 | |
| 61 | static void map_pages(struct list_head *list) |
| 62 | { |
| 63 | struct page *page; |
| 64 | |
| 65 | list_for_each_entry(page, list, lru) { |
| 66 | arch_alloc_page(page, 0); |
| 67 | kernel_map_pages(page, 1, 1); |
| 68 | kasan_alloc_pages(page, 0); |
| 69 | } |
| 70 | } |
| 71 | |
| 72 | static inline bool migrate_async_suitable(int migratetype) |
| 73 | { |
| 74 | return is_migrate_cma(migratetype) || migratetype == MIGRATE_MOVABLE; |
| 75 | } |
| 76 | |
| 77 | #ifdef CONFIG_COMPACTION |
| 78 | |
| 79 | /* Do not skip compaction more than 64 times */ |
| 80 | #define COMPACT_MAX_DEFER_SHIFT 6 |
| 81 | |
| 82 | /* |
| 83 | * Compaction is deferred when compaction fails to result in a page |
| 84 | * allocation success. 1 << compact_defer_limit compactions are skipped up |
| 85 | * to a limit of 1 << COMPACT_MAX_DEFER_SHIFT |
| 86 | */ |
| 87 | void defer_compaction(struct zone *zone, int order) |
| 88 | { |
| 89 | zone->compact_considered = 0; |
| 90 | zone->compact_defer_shift++; |
| 91 | |
| 92 | if (order < zone->compact_order_failed) |
| 93 | zone->compact_order_failed = order; |
| 94 | |
| 95 | if (zone->compact_defer_shift > COMPACT_MAX_DEFER_SHIFT) |
| 96 | zone->compact_defer_shift = COMPACT_MAX_DEFER_SHIFT; |
| 97 | |
| 98 | trace_mm_compaction_defer_compaction(zone, order); |
| 99 | } |
| 100 | |
| 101 | /* Returns true if compaction should be skipped this time */ |
| 102 | bool compaction_deferred(struct zone *zone, int order) |
| 103 | { |
| 104 | unsigned long defer_limit = 1UL << zone->compact_defer_shift; |
| 105 | |
| 106 | if (order < zone->compact_order_failed) |
| 107 | return false; |
| 108 | |
| 109 | /* Avoid possible overflow */ |
| 110 | if (++zone->compact_considered > defer_limit) |
| 111 | zone->compact_considered = defer_limit; |
| 112 | |
| 113 | if (zone->compact_considered >= defer_limit) |
| 114 | return false; |
| 115 | |
| 116 | trace_mm_compaction_deferred(zone, order); |
| 117 | |
| 118 | return true; |
| 119 | } |
| 120 | |
| 121 | /* |
| 122 | * Update defer tracking counters after successful compaction of given order, |
| 123 | * which means an allocation either succeeded (alloc_success == true) or is |
| 124 | * expected to succeed. |
| 125 | */ |
| 126 | void compaction_defer_reset(struct zone *zone, int order, |
| 127 | bool alloc_success) |
| 128 | { |
| 129 | if (alloc_success) { |
| 130 | zone->compact_considered = 0; |
| 131 | zone->compact_defer_shift = 0; |
| 132 | } |
| 133 | if (order >= zone->compact_order_failed) |
| 134 | zone->compact_order_failed = order + 1; |
| 135 | |
| 136 | trace_mm_compaction_defer_reset(zone, order); |
| 137 | } |
| 138 | |
| 139 | /* Returns true if restarting compaction after many failures */ |
| 140 | bool compaction_restarting(struct zone *zone, int order) |
| 141 | { |
| 142 | if (order < zone->compact_order_failed) |
| 143 | return false; |
| 144 | |
| 145 | return zone->compact_defer_shift == COMPACT_MAX_DEFER_SHIFT && |
| 146 | zone->compact_considered >= 1UL << zone->compact_defer_shift; |
| 147 | } |
| 148 | |
| 149 | /* Returns true if the pageblock should be scanned for pages to isolate. */ |
| 150 | static inline bool isolation_suitable(struct compact_control *cc, |
| 151 | struct page *page) |
| 152 | { |
| 153 | if (cc->ignore_skip_hint) |
| 154 | return true; |
| 155 | |
| 156 | return !get_pageblock_skip(page); |
| 157 | } |
| 158 | |
| 159 | static void reset_cached_positions(struct zone *zone) |
| 160 | { |
| 161 | zone->compact_cached_migrate_pfn[0] = zone->zone_start_pfn; |
| 162 | zone->compact_cached_migrate_pfn[1] = zone->zone_start_pfn; |
| 163 | zone->compact_cached_free_pfn = |
| 164 | round_down(zone_end_pfn(zone) - 1, pageblock_nr_pages); |
| 165 | } |
| 166 | |
| 167 | /* |
| 168 | * This function is called to clear all cached information on pageblocks that |
| 169 | * should be skipped for page isolation when the migrate and free page scanner |
| 170 | * meet. |
| 171 | */ |
| 172 | static void __reset_isolation_suitable(struct zone *zone) |
| 173 | { |
| 174 | unsigned long start_pfn = zone->zone_start_pfn; |
| 175 | unsigned long end_pfn = zone_end_pfn(zone); |
| 176 | unsigned long pfn; |
| 177 | |
| 178 | zone->compact_blockskip_flush = false; |
| 179 | |
| 180 | /* Walk the zone and mark every pageblock as suitable for isolation */ |
| 181 | for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) { |
| 182 | struct page *page; |
| 183 | |
| 184 | cond_resched(); |
| 185 | |
| 186 | if (!pfn_valid(pfn)) |
| 187 | continue; |
| 188 | |
| 189 | page = pfn_to_page(pfn); |
| 190 | if (zone != page_zone(page)) |
| 191 | continue; |
| 192 | |
| 193 | clear_pageblock_skip(page); |
| 194 | } |
| 195 | |
| 196 | reset_cached_positions(zone); |
| 197 | } |
| 198 | |
| 199 | void reset_isolation_suitable(pg_data_t *pgdat) |
| 200 | { |
| 201 | int zoneid; |
| 202 | |
| 203 | for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) { |
| 204 | struct zone *zone = &pgdat->node_zones[zoneid]; |
| 205 | if (!populated_zone(zone)) |
| 206 | continue; |
| 207 | |
| 208 | /* Only flush if a full compaction finished recently */ |
| 209 | if (zone->compact_blockskip_flush) |
| 210 | __reset_isolation_suitable(zone); |
| 211 | } |
| 212 | } |
| 213 | |
| 214 | /* |
| 215 | * If no pages were isolated then mark this pageblock to be skipped in the |
| 216 | * future. The information is later cleared by __reset_isolation_suitable(). |
| 217 | */ |
| 218 | static void update_pageblock_skip(struct compact_control *cc, |
| 219 | struct page *page, unsigned long nr_isolated, |
| 220 | bool migrate_scanner) |
| 221 | { |
| 222 | struct zone *zone = cc->zone; |
| 223 | unsigned long pfn; |
| 224 | |
| 225 | if (cc->ignore_skip_hint) |
| 226 | return; |
| 227 | |
| 228 | if (!page) |
| 229 | return; |
| 230 | |
| 231 | if (nr_isolated) |
| 232 | return; |
| 233 | |
| 234 | set_pageblock_skip(page); |
| 235 | |
| 236 | pfn = page_to_pfn(page); |
| 237 | |
| 238 | /* Update where async and sync compaction should restart */ |
| 239 | if (migrate_scanner) { |
| 240 | if (pfn > zone->compact_cached_migrate_pfn[0]) |
| 241 | zone->compact_cached_migrate_pfn[0] = pfn; |
| 242 | if (cc->mode != MIGRATE_ASYNC && |
| 243 | pfn > zone->compact_cached_migrate_pfn[1]) |
| 244 | zone->compact_cached_migrate_pfn[1] = pfn; |
| 245 | } else { |
| 246 | if (pfn < zone->compact_cached_free_pfn) |
| 247 | zone->compact_cached_free_pfn = pfn; |
| 248 | } |
| 249 | } |
| 250 | #else |
| 251 | static inline bool isolation_suitable(struct compact_control *cc, |
| 252 | struct page *page) |
| 253 | { |
| 254 | return true; |
| 255 | } |
| 256 | |
| 257 | static void update_pageblock_skip(struct compact_control *cc, |
| 258 | struct page *page, unsigned long nr_isolated, |
| 259 | bool migrate_scanner) |
| 260 | { |
| 261 | } |
| 262 | #endif /* CONFIG_COMPACTION */ |
| 263 | |
| 264 | /* |
| 265 | * Compaction requires the taking of some coarse locks that are potentially |
| 266 | * very heavily contended. For async compaction, back out if the lock cannot |
| 267 | * be taken immediately. For sync compaction, spin on the lock if needed. |
| 268 | * |
| 269 | * Returns true if the lock is held |
| 270 | * Returns false if the lock is not held and compaction should abort |
| 271 | */ |
| 272 | static bool compact_trylock_irqsave(spinlock_t *lock, unsigned long *flags, |
| 273 | struct compact_control *cc) |
| 274 | { |
| 275 | if (cc->mode == MIGRATE_ASYNC) { |
| 276 | if (!spin_trylock_irqsave(lock, *flags)) { |
| 277 | cc->contended = COMPACT_CONTENDED_LOCK; |
| 278 | return false; |
| 279 | } |
| 280 | } else { |
| 281 | spin_lock_irqsave(lock, *flags); |
| 282 | } |
| 283 | |
| 284 | return true; |
| 285 | } |
| 286 | |
| 287 | /* |
| 288 | * Compaction requires the taking of some coarse locks that are potentially |
| 289 | * very heavily contended. The lock should be periodically unlocked to avoid |
| 290 | * having disabled IRQs for a long time, even when there is nobody waiting on |
| 291 | * the lock. It might also be that allowing the IRQs will result in |
| 292 | * need_resched() becoming true. If scheduling is needed, async compaction |
| 293 | * aborts. Sync compaction schedules. |
| 294 | * Either compaction type will also abort if a fatal signal is pending. |
| 295 | * In either case if the lock was locked, it is dropped and not regained. |
| 296 | * |
| 297 | * Returns true if compaction should abort due to fatal signal pending, or |
| 298 | * async compaction due to need_resched() |
| 299 | * Returns false when compaction can continue (sync compaction might have |
| 300 | * scheduled) |
| 301 | */ |
| 302 | static bool compact_unlock_should_abort(spinlock_t *lock, |
| 303 | unsigned long flags, bool *locked, struct compact_control *cc) |
| 304 | { |
| 305 | if (*locked) { |
| 306 | spin_unlock_irqrestore(lock, flags); |
| 307 | *locked = false; |
| 308 | } |
| 309 | |
| 310 | if (fatal_signal_pending(current)) { |
| 311 | cc->contended = COMPACT_CONTENDED_SCHED; |
| 312 | return true; |
| 313 | } |
| 314 | |
| 315 | if (need_resched()) { |
| 316 | if (cc->mode == MIGRATE_ASYNC) { |
| 317 | cc->contended = COMPACT_CONTENDED_SCHED; |
| 318 | return true; |
| 319 | } |
| 320 | cond_resched(); |
| 321 | } |
| 322 | |
| 323 | return false; |
| 324 | } |
| 325 | |
| 326 | /* |
| 327 | * Aside from avoiding lock contention, compaction also periodically checks |
| 328 | * need_resched() and either schedules in sync compaction or aborts async |
| 329 | * compaction. This is similar to what compact_unlock_should_abort() does, but |
| 330 | * is used where no lock is concerned. |
| 331 | * |
| 332 | * Returns false when no scheduling was needed, or sync compaction scheduled. |
| 333 | * Returns true when async compaction should abort. |
| 334 | */ |
| 335 | static inline bool compact_should_abort(struct compact_control *cc) |
| 336 | { |
| 337 | /* async compaction aborts if contended */ |
| 338 | if (need_resched()) { |
| 339 | if (cc->mode == MIGRATE_ASYNC) { |
| 340 | cc->contended = COMPACT_CONTENDED_SCHED; |
| 341 | return true; |
| 342 | } |
| 343 | |
| 344 | cond_resched(); |
| 345 | } |
| 346 | |
| 347 | return false; |
| 348 | } |
| 349 | |
| 350 | /* |
| 351 | * Isolate free pages onto a private freelist. If @strict is true, will abort |
| 352 | * returning 0 on any invalid PFNs or non-free pages inside of the pageblock |
| 353 | * (even though it may still end up isolating some pages). |
| 354 | */ |
| 355 | static unsigned long isolate_freepages_block(struct compact_control *cc, |
| 356 | unsigned long *start_pfn, |
| 357 | unsigned long end_pfn, |
| 358 | struct list_head *freelist, |
| 359 | bool strict) |
| 360 | { |
| 361 | int nr_scanned = 0, total_isolated = 0; |
| 362 | struct page *cursor, *valid_page = NULL; |
| 363 | unsigned long flags = 0; |
| 364 | bool locked = false; |
| 365 | unsigned long blockpfn = *start_pfn; |
| 366 | |
| 367 | cursor = pfn_to_page(blockpfn); |
| 368 | |
| 369 | /* Isolate free pages. */ |
| 370 | for (; blockpfn < end_pfn; blockpfn++, cursor++) { |
| 371 | int isolated, i; |
| 372 | struct page *page = cursor; |
| 373 | |
| 374 | /* |
| 375 | * Periodically drop the lock (if held) regardless of its |
| 376 | * contention, to give chance to IRQs. Abort if fatal signal |
| 377 | * pending or async compaction detects need_resched() |
| 378 | */ |
| 379 | if (!(blockpfn % SWAP_CLUSTER_MAX) |
| 380 | && compact_unlock_should_abort(&cc->zone->lock, flags, |
| 381 | &locked, cc)) |
| 382 | break; |
| 383 | |
| 384 | nr_scanned++; |
| 385 | if (!pfn_valid_within(blockpfn)) |
| 386 | goto isolate_fail; |
| 387 | |
| 388 | if (!valid_page) |
| 389 | valid_page = page; |
| 390 | |
| 391 | /* |
| 392 | * For compound pages such as THP and hugetlbfs, we can save |
| 393 | * potentially a lot of iterations if we skip them at once. |
| 394 | * The check is racy, but we can consider only valid values |
| 395 | * and the only danger is skipping too much. |
| 396 | */ |
| 397 | if (PageCompound(page)) { |
| 398 | unsigned int comp_order = compound_order(page); |
| 399 | |
| 400 | if (likely(comp_order < MAX_ORDER)) { |
| 401 | blockpfn += (1UL << comp_order) - 1; |
| 402 | cursor += (1UL << comp_order) - 1; |
| 403 | } |
| 404 | |
| 405 | goto isolate_fail; |
| 406 | } |
| 407 | |
| 408 | if (!PageBuddy(page)) |
| 409 | goto isolate_fail; |
| 410 | |
| 411 | /* |
| 412 | * If we already hold the lock, we can skip some rechecking. |
| 413 | * Note that if we hold the lock now, checked_pageblock was |
| 414 | * already set in some previous iteration (or strict is true), |
| 415 | * so it is correct to skip the suitable migration target |
| 416 | * recheck as well. |
| 417 | */ |
| 418 | if (!locked) { |
| 419 | /* |
| 420 | * The zone lock must be held to isolate freepages. |
| 421 | * Unfortunately this is a very coarse lock and can be |
| 422 | * heavily contended if there are parallel allocations |
| 423 | * or parallel compactions. For async compaction do not |
| 424 | * spin on the lock and we acquire the lock as late as |
| 425 | * possible. |
| 426 | */ |
| 427 | locked = compact_trylock_irqsave(&cc->zone->lock, |
| 428 | &flags, cc); |
| 429 | if (!locked) |
| 430 | break; |
| 431 | |
| 432 | /* Recheck this is a buddy page under lock */ |
| 433 | if (!PageBuddy(page)) |
| 434 | goto isolate_fail; |
| 435 | } |
| 436 | |
| 437 | /* Found a free page, break it into order-0 pages */ |
| 438 | isolated = split_free_page(page); |
| 439 | total_isolated += isolated; |
| 440 | for (i = 0; i < isolated; i++) { |
| 441 | list_add(&page->lru, freelist); |
| 442 | page++; |
| 443 | } |
| 444 | |
| 445 | /* If a page was split, advance to the end of it */ |
| 446 | if (isolated) { |
| 447 | cc->nr_freepages += isolated; |
| 448 | if (!strict && |
| 449 | cc->nr_migratepages <= cc->nr_freepages) { |
| 450 | blockpfn += isolated; |
| 451 | break; |
| 452 | } |
| 453 | |
| 454 | blockpfn += isolated - 1; |
| 455 | cursor += isolated - 1; |
| 456 | continue; |
| 457 | } |
| 458 | |
| 459 | isolate_fail: |
| 460 | if (strict) |
| 461 | break; |
| 462 | else |
| 463 | continue; |
| 464 | |
| 465 | } |
| 466 | |
| 467 | /* |
| 468 | * There is a tiny chance that we have read bogus compound_order(), |
| 469 | * so be careful to not go outside of the pageblock. |
| 470 | */ |
| 471 | if (unlikely(blockpfn > end_pfn)) |
| 472 | blockpfn = end_pfn; |
| 473 | |
| 474 | trace_mm_compaction_isolate_freepages(*start_pfn, blockpfn, |
| 475 | nr_scanned, total_isolated); |
| 476 | |
| 477 | /* Record how far we have got within the block */ |
| 478 | *start_pfn = blockpfn; |
| 479 | |
| 480 | /* |
| 481 | * If strict isolation is requested by CMA then check that all the |
| 482 | * pages requested were isolated. If there were any failures, 0 is |
| 483 | * returned and CMA will fail. |
| 484 | */ |
| 485 | if (strict && blockpfn < end_pfn) |
| 486 | total_isolated = 0; |
| 487 | |
| 488 | if (locked) |
| 489 | spin_unlock_irqrestore(&cc->zone->lock, flags); |
| 490 | |
| 491 | /* Update the pageblock-skip if the whole pageblock was scanned */ |
| 492 | if (blockpfn == end_pfn) |
| 493 | update_pageblock_skip(cc, valid_page, total_isolated, false); |
| 494 | |
| 495 | count_compact_events(COMPACTFREE_SCANNED, nr_scanned); |
| 496 | if (total_isolated) |
| 497 | count_compact_events(COMPACTISOLATED, total_isolated); |
| 498 | return total_isolated; |
| 499 | } |
| 500 | |
| 501 | /** |
| 502 | * isolate_freepages_range() - isolate free pages. |
| 503 | * @start_pfn: The first PFN to start isolating. |
| 504 | * @end_pfn: The one-past-last PFN. |
| 505 | * |
| 506 | * Non-free pages, invalid PFNs, or zone boundaries within the |
| 507 | * [start_pfn, end_pfn) range are considered errors, cause function to |
| 508 | * undo its actions and return zero. |
| 509 | * |
| 510 | * Otherwise, function returns one-past-the-last PFN of isolated page |
| 511 | * (which may be greater then end_pfn if end fell in a middle of |
| 512 | * a free page). |
| 513 | */ |
| 514 | unsigned long |
| 515 | isolate_freepages_range(struct compact_control *cc, |
| 516 | unsigned long start_pfn, unsigned long end_pfn) |
| 517 | { |
| 518 | unsigned long isolated, pfn, block_start_pfn, block_end_pfn; |
| 519 | LIST_HEAD(freelist); |
| 520 | |
| 521 | pfn = start_pfn; |
| 522 | block_start_pfn = pfn & ~(pageblock_nr_pages - 1); |
| 523 | if (block_start_pfn < cc->zone->zone_start_pfn) |
| 524 | block_start_pfn = cc->zone->zone_start_pfn; |
| 525 | block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages); |
| 526 | |
| 527 | for (; pfn < end_pfn; pfn += isolated, |
| 528 | block_start_pfn = block_end_pfn, |
| 529 | block_end_pfn += pageblock_nr_pages) { |
| 530 | /* Protect pfn from changing by isolate_freepages_block */ |
| 531 | unsigned long isolate_start_pfn = pfn; |
| 532 | |
| 533 | block_end_pfn = min(block_end_pfn, end_pfn); |
| 534 | |
| 535 | /* |
| 536 | * pfn could pass the block_end_pfn if isolated freepage |
| 537 | * is more than pageblock order. In this case, we adjust |
| 538 | * scanning range to right one. |
| 539 | */ |
| 540 | if (pfn >= block_end_pfn) { |
| 541 | block_start_pfn = pfn & ~(pageblock_nr_pages - 1); |
| 542 | block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages); |
| 543 | block_end_pfn = min(block_end_pfn, end_pfn); |
| 544 | } |
| 545 | |
| 546 | if (!pageblock_pfn_to_page(block_start_pfn, |
| 547 | block_end_pfn, cc->zone)) |
| 548 | break; |
| 549 | |
| 550 | isolated = isolate_freepages_block(cc, &isolate_start_pfn, |
| 551 | block_end_pfn, &freelist, true); |
| 552 | |
| 553 | /* |
| 554 | * In strict mode, isolate_freepages_block() returns 0 if |
| 555 | * there are any holes in the block (ie. invalid PFNs or |
| 556 | * non-free pages). |
| 557 | */ |
| 558 | if (!isolated) |
| 559 | break; |
| 560 | |
| 561 | /* |
| 562 | * If we managed to isolate pages, it is always (1 << n) * |
| 563 | * pageblock_nr_pages for some non-negative n. (Max order |
| 564 | * page may span two pageblocks). |
| 565 | */ |
| 566 | } |
| 567 | |
| 568 | /* split_free_page does not map the pages */ |
| 569 | map_pages(&freelist); |
| 570 | |
| 571 | if (pfn < end_pfn) { |
| 572 | /* Loop terminated early, cleanup. */ |
| 573 | release_freepages(&freelist); |
| 574 | return 0; |
| 575 | } |
| 576 | |
| 577 | /* We don't use freelists for anything. */ |
| 578 | return pfn; |
| 579 | } |
| 580 | |
| 581 | /* Update the number of anon and file isolated pages in the zone */ |
| 582 | static void acct_isolated(struct zone *zone, struct compact_control *cc) |
| 583 | { |
| 584 | struct page *page; |
| 585 | unsigned int count[2] = { 0, }; |
| 586 | |
| 587 | if (list_empty(&cc->migratepages)) |
| 588 | return; |
| 589 | |
| 590 | list_for_each_entry(page, &cc->migratepages, lru) |
| 591 | count[!!page_is_file_cache(page)]++; |
| 592 | |
| 593 | mod_zone_page_state(zone, NR_ISOLATED_ANON, count[0]); |
| 594 | mod_zone_page_state(zone, NR_ISOLATED_FILE, count[1]); |
| 595 | } |
| 596 | |
| 597 | /* Similar to reclaim, but different enough that they don't share logic */ |
| 598 | static bool too_many_isolated(struct zone *zone) |
| 599 | { |
| 600 | unsigned long active, inactive, isolated; |
| 601 | |
| 602 | inactive = zone_page_state(zone, NR_INACTIVE_FILE) + |
| 603 | zone_page_state(zone, NR_INACTIVE_ANON); |
| 604 | active = zone_page_state(zone, NR_ACTIVE_FILE) + |
| 605 | zone_page_state(zone, NR_ACTIVE_ANON); |
| 606 | isolated = zone_page_state(zone, NR_ISOLATED_FILE) + |
| 607 | zone_page_state(zone, NR_ISOLATED_ANON); |
| 608 | |
| 609 | return isolated > (inactive + active) / 2; |
| 610 | } |
| 611 | |
| 612 | /** |
| 613 | * isolate_migratepages_block() - isolate all migrate-able pages within |
| 614 | * a single pageblock |
| 615 | * @cc: Compaction control structure. |
| 616 | * @low_pfn: The first PFN to isolate |
| 617 | * @end_pfn: The one-past-the-last PFN to isolate, within same pageblock |
| 618 | * @isolate_mode: Isolation mode to be used. |
| 619 | * |
| 620 | * Isolate all pages that can be migrated from the range specified by |
| 621 | * [low_pfn, end_pfn). The range is expected to be within same pageblock. |
| 622 | * Returns zero if there is a fatal signal pending, otherwise PFN of the |
| 623 | * first page that was not scanned (which may be both less, equal to or more |
| 624 | * than end_pfn). |
| 625 | * |
| 626 | * The pages are isolated on cc->migratepages list (not required to be empty), |
| 627 | * and cc->nr_migratepages is updated accordingly. The cc->migrate_pfn field |
| 628 | * is neither read nor updated. |
| 629 | */ |
| 630 | static unsigned long |
| 631 | isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, |
| 632 | unsigned long end_pfn, isolate_mode_t isolate_mode) |
| 633 | { |
| 634 | struct zone *zone = cc->zone; |
| 635 | unsigned long nr_scanned = 0, nr_isolated = 0; |
| 636 | struct list_head *migratelist = &cc->migratepages; |
| 637 | struct lruvec *lruvec; |
| 638 | unsigned long flags = 0; |
| 639 | bool locked = false; |
| 640 | struct page *page = NULL, *valid_page = NULL; |
| 641 | unsigned long start_pfn = low_pfn; |
| 642 | |
| 643 | /* |
| 644 | * Ensure that there are not too many pages isolated from the LRU |
| 645 | * list by either parallel reclaimers or compaction. If there are, |
| 646 | * delay for some time until fewer pages are isolated |
| 647 | */ |
| 648 | while (unlikely(too_many_isolated(zone))) { |
| 649 | /* async migration should just abort */ |
| 650 | if (cc->mode == MIGRATE_ASYNC) |
| 651 | return 0; |
| 652 | |
| 653 | congestion_wait(BLK_RW_ASYNC, HZ/10); |
| 654 | |
| 655 | if (fatal_signal_pending(current)) |
| 656 | return 0; |
| 657 | } |
| 658 | |
| 659 | if (compact_should_abort(cc)) |
| 660 | return 0; |
| 661 | |
| 662 | /* Time to isolate some pages for migration */ |
| 663 | for (; low_pfn < end_pfn; low_pfn++) { |
| 664 | bool is_lru; |
| 665 | |
| 666 | /* |
| 667 | * Periodically drop the lock (if held) regardless of its |
| 668 | * contention, to give chance to IRQs. Abort async compaction |
| 669 | * if contended. |
| 670 | */ |
| 671 | if (!(low_pfn % SWAP_CLUSTER_MAX) |
| 672 | && compact_unlock_should_abort(&zone->lru_lock, flags, |
| 673 | &locked, cc)) |
| 674 | break; |
| 675 | |
| 676 | if (!pfn_valid_within(low_pfn)) |
| 677 | continue; |
| 678 | nr_scanned++; |
| 679 | |
| 680 | page = pfn_to_page(low_pfn); |
| 681 | |
| 682 | if (!valid_page) |
| 683 | valid_page = page; |
| 684 | |
| 685 | /* |
| 686 | * Skip if free. We read page order here without zone lock |
| 687 | * which is generally unsafe, but the race window is small and |
| 688 | * the worst thing that can happen is that we skip some |
| 689 | * potential isolation targets. |
| 690 | */ |
| 691 | if (PageBuddy(page)) { |
| 692 | unsigned long freepage_order = page_order_unsafe(page); |
| 693 | |
| 694 | /* |
| 695 | * Without lock, we cannot be sure that what we got is |
| 696 | * a valid page order. Consider only values in the |
| 697 | * valid order range to prevent low_pfn overflow. |
| 698 | */ |
| 699 | if (freepage_order > 0 && freepage_order < MAX_ORDER) |
| 700 | low_pfn += (1UL << freepage_order) - 1; |
| 701 | continue; |
| 702 | } |
| 703 | |
| 704 | /* |
| 705 | * Check may be lockless but that's ok as we recheck later. |
| 706 | * It's possible to migrate LRU pages and balloon pages |
| 707 | * Skip any other type of page |
| 708 | */ |
| 709 | is_lru = PageLRU(page); |
| 710 | if (!is_lru) { |
| 711 | if (unlikely(balloon_page_movable(page))) { |
| 712 | if (balloon_page_isolate(page)) { |
| 713 | /* Successfully isolated */ |
| 714 | goto isolate_success; |
| 715 | } |
| 716 | } |
| 717 | } |
| 718 | |
| 719 | /* |
| 720 | * Regardless of being on LRU, compound pages such as THP and |
| 721 | * hugetlbfs are not to be compacted. We can potentially save |
| 722 | * a lot of iterations if we skip them at once. The check is |
| 723 | * racy, but we can consider only valid values and the only |
| 724 | * danger is skipping too much. |
| 725 | */ |
| 726 | if (PageCompound(page)) { |
| 727 | unsigned int comp_order = compound_order(page); |
| 728 | |
| 729 | if (likely(comp_order < MAX_ORDER)) |
| 730 | low_pfn += (1UL << comp_order) - 1; |
| 731 | |
| 732 | continue; |
| 733 | } |
| 734 | |
| 735 | if (!is_lru) |
| 736 | continue; |
| 737 | |
| 738 | /* |
| 739 | * Migration will fail if an anonymous page is pinned in memory, |
| 740 | * so avoid taking lru_lock and isolating it unnecessarily in an |
| 741 | * admittedly racy check. |
| 742 | */ |
| 743 | if (!page_mapping(page) && |
| 744 | page_count(page) > page_mapcount(page)) |
| 745 | continue; |
| 746 | |
| 747 | /* If we already hold the lock, we can skip some rechecking */ |
| 748 | if (!locked) { |
| 749 | locked = compact_trylock_irqsave(&zone->lru_lock, |
| 750 | &flags, cc); |
| 751 | if (!locked) |
| 752 | break; |
| 753 | |
| 754 | /* Recheck PageLRU and PageCompound under lock */ |
| 755 | if (!PageLRU(page)) |
| 756 | continue; |
| 757 | |
| 758 | /* |
| 759 | * Page become compound since the non-locked check, |
| 760 | * and it's on LRU. It can only be a THP so the order |
| 761 | * is safe to read and it's 0 for tail pages. |
| 762 | */ |
| 763 | if (unlikely(PageCompound(page))) { |
| 764 | low_pfn += (1UL << compound_order(page)) - 1; |
| 765 | continue; |
| 766 | } |
| 767 | } |
| 768 | |
| 769 | lruvec = mem_cgroup_page_lruvec(page, zone); |
| 770 | |
| 771 | /* Try isolate the page */ |
| 772 | if (__isolate_lru_page(page, isolate_mode) != 0) |
| 773 | continue; |
| 774 | |
| 775 | VM_BUG_ON_PAGE(PageCompound(page), page); |
| 776 | |
| 777 | /* Successfully isolated */ |
| 778 | del_page_from_lru_list(page, lruvec, page_lru(page)); |
| 779 | |
| 780 | isolate_success: |
| 781 | list_add(&page->lru, migratelist); |
| 782 | cc->nr_migratepages++; |
| 783 | nr_isolated++; |
| 784 | |
| 785 | /* Avoid isolating too much */ |
| 786 | if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) { |
| 787 | ++low_pfn; |
| 788 | break; |
| 789 | } |
| 790 | } |
| 791 | |
| 792 | /* |
| 793 | * The PageBuddy() check could have potentially brought us outside |
| 794 | * the range to be scanned. |
| 795 | */ |
| 796 | if (unlikely(low_pfn > end_pfn)) |
| 797 | low_pfn = end_pfn; |
| 798 | |
| 799 | if (locked) |
| 800 | spin_unlock_irqrestore(&zone->lru_lock, flags); |
| 801 | |
| 802 | /* |
| 803 | * Update the pageblock-skip information and cached scanner pfn, |
| 804 | * if the whole pageblock was scanned without isolating any page. |
| 805 | */ |
| 806 | if (low_pfn == end_pfn) |
| 807 | update_pageblock_skip(cc, valid_page, nr_isolated, true); |
| 808 | |
| 809 | trace_mm_compaction_isolate_migratepages(start_pfn, low_pfn, |
| 810 | nr_scanned, nr_isolated); |
| 811 | |
| 812 | count_compact_events(COMPACTMIGRATE_SCANNED, nr_scanned); |
| 813 | if (nr_isolated) |
| 814 | count_compact_events(COMPACTISOLATED, nr_isolated); |
| 815 | |
| 816 | return low_pfn; |
| 817 | } |
| 818 | |
| 819 | /** |
| 820 | * isolate_migratepages_range() - isolate migrate-able pages in a PFN range |
| 821 | * @cc: Compaction control structure. |
| 822 | * @start_pfn: The first PFN to start isolating. |
| 823 | * @end_pfn: The one-past-last PFN. |
| 824 | * |
| 825 | * Returns zero if isolation fails fatally due to e.g. pending signal. |
| 826 | * Otherwise, function returns one-past-the-last PFN of isolated page |
| 827 | * (which may be greater than end_pfn if end fell in a middle of a THP page). |
| 828 | */ |
| 829 | unsigned long |
| 830 | isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn, |
| 831 | unsigned long end_pfn) |
| 832 | { |
| 833 | unsigned long pfn, block_start_pfn, block_end_pfn; |
| 834 | |
| 835 | /* Scan block by block. First and last block may be incomplete */ |
| 836 | pfn = start_pfn; |
| 837 | block_start_pfn = pfn & ~(pageblock_nr_pages - 1); |
| 838 | if (block_start_pfn < cc->zone->zone_start_pfn) |
| 839 | block_start_pfn = cc->zone->zone_start_pfn; |
| 840 | block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages); |
| 841 | |
| 842 | for (; pfn < end_pfn; pfn = block_end_pfn, |
| 843 | block_start_pfn = block_end_pfn, |
| 844 | block_end_pfn += pageblock_nr_pages) { |
| 845 | |
| 846 | block_end_pfn = min(block_end_pfn, end_pfn); |
| 847 | |
| 848 | if (!pageblock_pfn_to_page(block_start_pfn, |
| 849 | block_end_pfn, cc->zone)) |
| 850 | continue; |
| 851 | |
| 852 | pfn = isolate_migratepages_block(cc, pfn, block_end_pfn, |
| 853 | ISOLATE_UNEVICTABLE); |
| 854 | |
| 855 | if (!pfn) |
| 856 | break; |
| 857 | |
| 858 | if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) |
| 859 | break; |
| 860 | } |
| 861 | acct_isolated(cc->zone, cc); |
| 862 | |
| 863 | return pfn; |
| 864 | } |
| 865 | |
| 866 | #endif /* CONFIG_COMPACTION || CONFIG_CMA */ |
| 867 | #ifdef CONFIG_COMPACTION |
| 868 | |
| 869 | /* Returns true if the page is within a block suitable for migration to */ |
| 870 | static bool suitable_migration_target(struct page *page) |
| 871 | { |
| 872 | /* If the page is a large free page, then disallow migration */ |
| 873 | if (PageBuddy(page)) { |
| 874 | /* |
| 875 | * We are checking page_order without zone->lock taken. But |
| 876 | * the only small danger is that we skip a potentially suitable |
| 877 | * pageblock, so it's not worth to check order for valid range. |
| 878 | */ |
| 879 | if (page_order_unsafe(page) >= pageblock_order) |
| 880 | return false; |
| 881 | } |
| 882 | |
| 883 | /* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */ |
| 884 | if (migrate_async_suitable(get_pageblock_migratetype(page))) |
| 885 | return true; |
| 886 | |
| 887 | /* Otherwise skip the block */ |
| 888 | return false; |
| 889 | } |
| 890 | |
| 891 | /* |
| 892 | * Test whether the free scanner has reached the same or lower pageblock than |
| 893 | * the migration scanner, and compaction should thus terminate. |
| 894 | */ |
| 895 | static inline bool compact_scanners_met(struct compact_control *cc) |
| 896 | { |
| 897 | return (cc->free_pfn >> pageblock_order) |
| 898 | <= (cc->migrate_pfn >> pageblock_order); |
| 899 | } |
| 900 | |
| 901 | /* |
| 902 | * Based on information in the current compact_control, find blocks |
| 903 | * suitable for isolating free pages from and then isolate them. |
| 904 | */ |
| 905 | static void isolate_freepages(struct compact_control *cc) |
| 906 | { |
| 907 | struct zone *zone = cc->zone; |
| 908 | struct page *page; |
| 909 | unsigned long block_start_pfn; /* start of current pageblock */ |
| 910 | unsigned long isolate_start_pfn; /* exact pfn we start at */ |
| 911 | unsigned long block_end_pfn; /* end of current pageblock */ |
| 912 | unsigned long low_pfn; /* lowest pfn scanner is able to scan */ |
| 913 | struct list_head *freelist = &cc->freepages; |
| 914 | |
| 915 | /* |
| 916 | * Initialise the free scanner. The starting point is where we last |
| 917 | * successfully isolated from, zone-cached value, or the end of the |
| 918 | * zone when isolating for the first time. For looping we also need |
| 919 | * this pfn aligned down to the pageblock boundary, because we do |
| 920 | * block_start_pfn -= pageblock_nr_pages in the for loop. |
| 921 | * For ending point, take care when isolating in last pageblock of a |
| 922 | * a zone which ends in the middle of a pageblock. |
| 923 | * The low boundary is the end of the pageblock the migration scanner |
| 924 | * is using. |
| 925 | */ |
| 926 | isolate_start_pfn = cc->free_pfn; |
| 927 | block_start_pfn = cc->free_pfn & ~(pageblock_nr_pages-1); |
| 928 | block_end_pfn = min(block_start_pfn + pageblock_nr_pages, |
| 929 | zone_end_pfn(zone)); |
| 930 | low_pfn = ALIGN(cc->migrate_pfn + 1, pageblock_nr_pages); |
| 931 | |
| 932 | /* |
| 933 | * Isolate free pages until enough are available to migrate the |
| 934 | * pages on cc->migratepages. We stop searching if the migrate |
| 935 | * and free page scanners meet or enough free pages are isolated. |
| 936 | */ |
| 937 | for (; block_start_pfn >= low_pfn; |
| 938 | block_end_pfn = block_start_pfn, |
| 939 | block_start_pfn -= pageblock_nr_pages, |
| 940 | isolate_start_pfn = block_start_pfn) { |
| 941 | |
| 942 | /* |
| 943 | * This can iterate a massively long zone without finding any |
| 944 | * suitable migration targets, so periodically check if we need |
| 945 | * to schedule, or even abort async compaction. |
| 946 | */ |
| 947 | if (!(block_start_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages)) |
| 948 | && compact_should_abort(cc)) |
| 949 | break; |
| 950 | |
| 951 | page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn, |
| 952 | zone); |
| 953 | if (!page) |
| 954 | continue; |
| 955 | |
| 956 | /* Check the block is suitable for migration */ |
| 957 | if (!suitable_migration_target(page)) |
| 958 | continue; |
| 959 | |
| 960 | /* If isolation recently failed, do not retry */ |
| 961 | if (!isolation_suitable(cc, page)) |
| 962 | continue; |
| 963 | |
| 964 | /* Found a block suitable for isolating free pages from. */ |
| 965 | isolate_freepages_block(cc, &isolate_start_pfn, |
| 966 | block_end_pfn, freelist, false); |
| 967 | |
| 968 | /* |
| 969 | * If we isolated enough freepages, or aborted due to async |
| 970 | * compaction being contended, terminate the loop. |
| 971 | * Remember where the free scanner should restart next time, |
| 972 | * which is where isolate_freepages_block() left off. |
| 973 | * But if it scanned the whole pageblock, isolate_start_pfn |
| 974 | * now points at block_end_pfn, which is the start of the next |
| 975 | * pageblock. |
| 976 | * In that case we will however want to restart at the start |
| 977 | * of the previous pageblock. |
| 978 | */ |
| 979 | if ((cc->nr_freepages >= cc->nr_migratepages) |
| 980 | || cc->contended) { |
| 981 | if (isolate_start_pfn >= block_end_pfn) |
| 982 | isolate_start_pfn = |
| 983 | block_start_pfn - pageblock_nr_pages; |
| 984 | break; |
| 985 | } else { |
| 986 | /* |
| 987 | * isolate_freepages_block() should not terminate |
| 988 | * prematurely unless contended, or isolated enough |
| 989 | */ |
| 990 | VM_BUG_ON(isolate_start_pfn < block_end_pfn); |
| 991 | } |
| 992 | } |
| 993 | |
| 994 | /* split_free_page does not map the pages */ |
| 995 | map_pages(freelist); |
| 996 | |
| 997 | /* |
| 998 | * Record where the free scanner will restart next time. Either we |
| 999 | * broke from the loop and set isolate_start_pfn based on the last |
| 1000 | * call to isolate_freepages_block(), or we met the migration scanner |
| 1001 | * and the loop terminated due to isolate_start_pfn < low_pfn |
| 1002 | */ |
| 1003 | cc->free_pfn = isolate_start_pfn; |
| 1004 | } |
| 1005 | |
| 1006 | /* |
| 1007 | * This is a migrate-callback that "allocates" freepages by taking pages |
| 1008 | * from the isolated freelists in the block we are migrating to. |
| 1009 | */ |
| 1010 | static struct page *compaction_alloc(struct page *migratepage, |
| 1011 | unsigned long data, |
| 1012 | int **result) |
| 1013 | { |
| 1014 | struct compact_control *cc = (struct compact_control *)data; |
| 1015 | struct page *freepage; |
| 1016 | |
| 1017 | /* |
| 1018 | * Isolate free pages if necessary, and if we are not aborting due to |
| 1019 | * contention. |
| 1020 | */ |
| 1021 | if (list_empty(&cc->freepages)) { |
| 1022 | if (!cc->contended) |
| 1023 | isolate_freepages(cc); |
| 1024 | |
| 1025 | if (list_empty(&cc->freepages)) |
| 1026 | return NULL; |
| 1027 | } |
| 1028 | |
| 1029 | freepage = list_entry(cc->freepages.next, struct page, lru); |
| 1030 | list_del(&freepage->lru); |
| 1031 | cc->nr_freepages--; |
| 1032 | |
| 1033 | return freepage; |
| 1034 | } |
| 1035 | |
| 1036 | /* |
| 1037 | * This is a migrate-callback that "frees" freepages back to the isolated |
| 1038 | * freelist. All pages on the freelist are from the same zone, so there is no |
| 1039 | * special handling needed for NUMA. |
| 1040 | */ |
| 1041 | static void compaction_free(struct page *page, unsigned long data) |
| 1042 | { |
| 1043 | struct compact_control *cc = (struct compact_control *)data; |
| 1044 | |
| 1045 | list_add(&page->lru, &cc->freepages); |
| 1046 | cc->nr_freepages++; |
| 1047 | } |
| 1048 | |
| 1049 | /* possible outcome of isolate_migratepages */ |
| 1050 | typedef enum { |
| 1051 | ISOLATE_ABORT, /* Abort compaction now */ |
| 1052 | ISOLATE_NONE, /* No pages isolated, continue scanning */ |
| 1053 | ISOLATE_SUCCESS, /* Pages isolated, migrate */ |
| 1054 | } isolate_migrate_t; |
| 1055 | |
| 1056 | /* |
| 1057 | * Allow userspace to control policy on scanning the unevictable LRU for |
| 1058 | * compactable pages. |
| 1059 | */ |
| 1060 | int sysctl_compact_unevictable_allowed __read_mostly = 1; |
| 1061 | |
| 1062 | /* |
| 1063 | * Isolate all pages that can be migrated from the first suitable block, |
| 1064 | * starting at the block pointed to by the migrate scanner pfn within |
| 1065 | * compact_control. |
| 1066 | */ |
| 1067 | static isolate_migrate_t isolate_migratepages(struct zone *zone, |
| 1068 | struct compact_control *cc) |
| 1069 | { |
| 1070 | unsigned long block_start_pfn; |
| 1071 | unsigned long block_end_pfn; |
| 1072 | unsigned long low_pfn; |
| 1073 | unsigned long isolate_start_pfn; |
| 1074 | struct page *page; |
| 1075 | const isolate_mode_t isolate_mode = |
| 1076 | (sysctl_compact_unevictable_allowed ? ISOLATE_UNEVICTABLE : 0) | |
| 1077 | (cc->mode == MIGRATE_ASYNC ? ISOLATE_ASYNC_MIGRATE : 0); |
| 1078 | |
| 1079 | /* |
| 1080 | * Start at where we last stopped, or beginning of the zone as |
| 1081 | * initialized by compact_zone() |
| 1082 | */ |
| 1083 | low_pfn = cc->migrate_pfn; |
| 1084 | block_start_pfn = cc->migrate_pfn & ~(pageblock_nr_pages - 1); |
| 1085 | if (block_start_pfn < zone->zone_start_pfn) |
| 1086 | block_start_pfn = zone->zone_start_pfn; |
| 1087 | |
| 1088 | /* Only scan within a pageblock boundary */ |
| 1089 | block_end_pfn = ALIGN(low_pfn + 1, pageblock_nr_pages); |
| 1090 | |
| 1091 | /* |
| 1092 | * Iterate over whole pageblocks until we find the first suitable. |
| 1093 | * Do not cross the free scanner. |
| 1094 | */ |
| 1095 | for (; block_end_pfn <= cc->free_pfn; |
| 1096 | low_pfn = block_end_pfn, |
| 1097 | block_start_pfn = block_end_pfn, |
| 1098 | block_end_pfn += pageblock_nr_pages) { |
| 1099 | |
| 1100 | /* |
| 1101 | * This can potentially iterate a massively long zone with |
| 1102 | * many pageblocks unsuitable, so periodically check if we |
| 1103 | * need to schedule, or even abort async compaction. |
| 1104 | */ |
| 1105 | if (!(low_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages)) |
| 1106 | && compact_should_abort(cc)) |
| 1107 | break; |
| 1108 | |
| 1109 | page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn, |
| 1110 | zone); |
| 1111 | if (!page) |
| 1112 | continue; |
| 1113 | |
| 1114 | /* If isolation recently failed, do not retry */ |
| 1115 | if (!isolation_suitable(cc, page)) |
| 1116 | continue; |
| 1117 | |
| 1118 | /* |
| 1119 | * For async compaction, also only scan in MOVABLE blocks. |
| 1120 | * Async compaction is optimistic to see if the minimum amount |
| 1121 | * of work satisfies the allocation. |
| 1122 | */ |
| 1123 | if (cc->mode == MIGRATE_ASYNC && |
| 1124 | !migrate_async_suitable(get_pageblock_migratetype(page))) |
| 1125 | continue; |
| 1126 | |
| 1127 | /* Perform the isolation */ |
| 1128 | isolate_start_pfn = low_pfn; |
| 1129 | low_pfn = isolate_migratepages_block(cc, low_pfn, |
| 1130 | block_end_pfn, isolate_mode); |
| 1131 | |
| 1132 | if (!low_pfn || cc->contended) { |
| 1133 | acct_isolated(zone, cc); |
| 1134 | return ISOLATE_ABORT; |
| 1135 | } |
| 1136 | |
| 1137 | /* |
| 1138 | * Record where we could have freed pages by migration and not |
| 1139 | * yet flushed them to buddy allocator. |
| 1140 | * - this is the lowest page that could have been isolated and |
| 1141 | * then freed by migration. |
| 1142 | */ |
| 1143 | if (cc->nr_migratepages && !cc->last_migrated_pfn) |
| 1144 | cc->last_migrated_pfn = isolate_start_pfn; |
| 1145 | |
| 1146 | /* |
| 1147 | * Either we isolated something and proceed with migration. Or |
| 1148 | * we failed and compact_zone should decide if we should |
| 1149 | * continue or not. |
| 1150 | */ |
| 1151 | break; |
| 1152 | } |
| 1153 | |
| 1154 | acct_isolated(zone, cc); |
| 1155 | /* Record where migration scanner will be restarted. */ |
| 1156 | cc->migrate_pfn = low_pfn; |
| 1157 | |
| 1158 | return cc->nr_migratepages ? ISOLATE_SUCCESS : ISOLATE_NONE; |
| 1159 | } |
| 1160 | |
| 1161 | /* |
| 1162 | * order == -1 is expected when compacting via |
| 1163 | * /proc/sys/vm/compact_memory |
| 1164 | */ |
| 1165 | static inline bool is_via_compact_memory(int order) |
| 1166 | { |
| 1167 | return order == -1; |
| 1168 | } |
| 1169 | |
| 1170 | static int __compact_finished(struct zone *zone, struct compact_control *cc, |
| 1171 | const int migratetype) |
| 1172 | { |
| 1173 | unsigned int order; |
| 1174 | unsigned long watermark; |
| 1175 | |
| 1176 | if (cc->contended || fatal_signal_pending(current)) |
| 1177 | return COMPACT_CONTENDED; |
| 1178 | |
| 1179 | /* Compaction run completes if the migrate and free scanner meet */ |
| 1180 | if (compact_scanners_met(cc)) { |
| 1181 | /* Let the next compaction start anew. */ |
| 1182 | reset_cached_positions(zone); |
| 1183 | |
| 1184 | /* |
| 1185 | * Mark that the PG_migrate_skip information should be cleared |
| 1186 | * by kswapd when it goes to sleep. kcompactd does not set the |
| 1187 | * flag itself as the decision to be clear should be directly |
| 1188 | * based on an allocation request. |
| 1189 | */ |
| 1190 | if (cc->direct_compaction) |
| 1191 | zone->compact_blockskip_flush = true; |
| 1192 | |
| 1193 | return COMPACT_COMPLETE; |
| 1194 | } |
| 1195 | |
| 1196 | if (is_via_compact_memory(cc->order)) |
| 1197 | return COMPACT_CONTINUE; |
| 1198 | |
| 1199 | /* Compaction run is not finished if the watermark is not met */ |
| 1200 | watermark = low_wmark_pages(zone); |
| 1201 | |
| 1202 | if (!zone_watermark_ok(zone, cc->order, watermark, cc->classzone_idx, |
| 1203 | cc->alloc_flags)) |
| 1204 | return COMPACT_CONTINUE; |
| 1205 | |
| 1206 | /* Direct compactor: Is a suitable page free? */ |
| 1207 | for (order = cc->order; order < MAX_ORDER; order++) { |
| 1208 | struct free_area *area = &zone->free_area[order]; |
| 1209 | bool can_steal; |
| 1210 | |
| 1211 | /* Job done if page is free of the right migratetype */ |
| 1212 | if (!list_empty(&area->free_list[migratetype])) |
| 1213 | return COMPACT_PARTIAL; |
| 1214 | |
| 1215 | #ifdef CONFIG_CMA |
| 1216 | /* MIGRATE_MOVABLE can fallback on MIGRATE_CMA */ |
| 1217 | if (migratetype == MIGRATE_MOVABLE && |
| 1218 | !list_empty(&area->free_list[MIGRATE_CMA])) |
| 1219 | return COMPACT_PARTIAL; |
| 1220 | #endif |
| 1221 | /* |
| 1222 | * Job done if allocation would steal freepages from |
| 1223 | * other migratetype buddy lists. |
| 1224 | */ |
| 1225 | if (find_suitable_fallback(area, order, migratetype, |
| 1226 | true, &can_steal) != -1) |
| 1227 | return COMPACT_PARTIAL; |
| 1228 | } |
| 1229 | |
| 1230 | return COMPACT_NO_SUITABLE_PAGE; |
| 1231 | } |
| 1232 | |
| 1233 | static int compact_finished(struct zone *zone, struct compact_control *cc, |
| 1234 | const int migratetype) |
| 1235 | { |
| 1236 | int ret; |
| 1237 | |
| 1238 | ret = __compact_finished(zone, cc, migratetype); |
| 1239 | trace_mm_compaction_finished(zone, cc->order, ret); |
| 1240 | if (ret == COMPACT_NO_SUITABLE_PAGE) |
| 1241 | ret = COMPACT_CONTINUE; |
| 1242 | |
| 1243 | return ret; |
| 1244 | } |
| 1245 | |
| 1246 | /* |
| 1247 | * compaction_suitable: Is this suitable to run compaction on this zone now? |
| 1248 | * Returns |
| 1249 | * COMPACT_SKIPPED - If there are too few free pages for compaction |
| 1250 | * COMPACT_PARTIAL - If the allocation would succeed without compaction |
| 1251 | * COMPACT_CONTINUE - If compaction should run now |
| 1252 | */ |
| 1253 | static unsigned long __compaction_suitable(struct zone *zone, int order, |
| 1254 | int alloc_flags, int classzone_idx) |
| 1255 | { |
| 1256 | int fragindex; |
| 1257 | unsigned long watermark; |
| 1258 | |
| 1259 | if (is_via_compact_memory(order)) |
| 1260 | return COMPACT_CONTINUE; |
| 1261 | |
| 1262 | watermark = low_wmark_pages(zone); |
| 1263 | /* |
| 1264 | * If watermarks for high-order allocation are already met, there |
| 1265 | * should be no need for compaction at all. |
| 1266 | */ |
| 1267 | if (zone_watermark_ok(zone, order, watermark, classzone_idx, |
| 1268 | alloc_flags)) |
| 1269 | return COMPACT_PARTIAL; |
| 1270 | |
| 1271 | /* |
| 1272 | * Watermarks for order-0 must be met for compaction. Note the 2UL. |
| 1273 | * This is because during migration, copies of pages need to be |
| 1274 | * allocated and for a short time, the footprint is higher |
| 1275 | */ |
| 1276 | watermark += (2UL << order); |
| 1277 | if (!zone_watermark_ok(zone, 0, watermark, classzone_idx, alloc_flags)) |
| 1278 | return COMPACT_SKIPPED; |
| 1279 | |
| 1280 | /* |
| 1281 | * fragmentation index determines if allocation failures are due to |
| 1282 | * low memory or external fragmentation |
| 1283 | * |
| 1284 | * index of -1000 would imply allocations might succeed depending on |
| 1285 | * watermarks, but we already failed the high-order watermark check |
| 1286 | * index towards 0 implies failure is due to lack of memory |
| 1287 | * index towards 1000 implies failure is due to fragmentation |
| 1288 | * |
| 1289 | * Only compact if a failure would be due to fragmentation. |
| 1290 | */ |
| 1291 | fragindex = fragmentation_index(zone, order); |
| 1292 | if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold) |
| 1293 | return COMPACT_NOT_SUITABLE_ZONE; |
| 1294 | |
| 1295 | return COMPACT_CONTINUE; |
| 1296 | } |
| 1297 | |
| 1298 | unsigned long compaction_suitable(struct zone *zone, int order, |
| 1299 | int alloc_flags, int classzone_idx) |
| 1300 | { |
| 1301 | unsigned long ret; |
| 1302 | |
| 1303 | ret = __compaction_suitable(zone, order, alloc_flags, classzone_idx); |
| 1304 | trace_mm_compaction_suitable(zone, order, ret); |
| 1305 | if (ret == COMPACT_NOT_SUITABLE_ZONE) |
| 1306 | ret = COMPACT_SKIPPED; |
| 1307 | |
| 1308 | return ret; |
| 1309 | } |
| 1310 | |
| 1311 | static int compact_zone(struct zone *zone, struct compact_control *cc) |
| 1312 | { |
| 1313 | int ret; |
| 1314 | unsigned long start_pfn = zone->zone_start_pfn; |
| 1315 | unsigned long end_pfn = zone_end_pfn(zone); |
| 1316 | const int migratetype = gfpflags_to_migratetype(cc->gfp_mask); |
| 1317 | const bool sync = cc->mode != MIGRATE_ASYNC; |
| 1318 | |
| 1319 | ret = compaction_suitable(zone, cc->order, cc->alloc_flags, |
| 1320 | cc->classzone_idx); |
| 1321 | switch (ret) { |
| 1322 | case COMPACT_PARTIAL: |
| 1323 | case COMPACT_SKIPPED: |
| 1324 | /* Compaction is likely to fail */ |
| 1325 | return ret; |
| 1326 | case COMPACT_CONTINUE: |
| 1327 | /* Fall through to compaction */ |
| 1328 | ; |
| 1329 | } |
| 1330 | |
| 1331 | /* |
| 1332 | * Clear pageblock skip if there were failures recently and compaction |
| 1333 | * is about to be retried after being deferred. |
| 1334 | */ |
| 1335 | if (compaction_restarting(zone, cc->order)) |
| 1336 | __reset_isolation_suitable(zone); |
| 1337 | |
| 1338 | /* |
| 1339 | * Setup to move all movable pages to the end of the zone. Used cached |
| 1340 | * information on where the scanners should start but check that it |
| 1341 | * is initialised by ensuring the values are within zone boundaries. |
| 1342 | */ |
| 1343 | cc->migrate_pfn = zone->compact_cached_migrate_pfn[sync]; |
| 1344 | cc->free_pfn = zone->compact_cached_free_pfn; |
| 1345 | if (cc->free_pfn < start_pfn || cc->free_pfn >= end_pfn) { |
| 1346 | cc->free_pfn = round_down(end_pfn - 1, pageblock_nr_pages); |
| 1347 | zone->compact_cached_free_pfn = cc->free_pfn; |
| 1348 | } |
| 1349 | if (cc->migrate_pfn < start_pfn || cc->migrate_pfn >= end_pfn) { |
| 1350 | cc->migrate_pfn = start_pfn; |
| 1351 | zone->compact_cached_migrate_pfn[0] = cc->migrate_pfn; |
| 1352 | zone->compact_cached_migrate_pfn[1] = cc->migrate_pfn; |
| 1353 | } |
| 1354 | cc->last_migrated_pfn = 0; |
| 1355 | |
| 1356 | trace_mm_compaction_begin(start_pfn, cc->migrate_pfn, |
| 1357 | cc->free_pfn, end_pfn, sync); |
| 1358 | |
| 1359 | migrate_prep_local(); |
| 1360 | |
| 1361 | while ((ret = compact_finished(zone, cc, migratetype)) == |
| 1362 | COMPACT_CONTINUE) { |
| 1363 | int err; |
| 1364 | |
| 1365 | switch (isolate_migratepages(zone, cc)) { |
| 1366 | case ISOLATE_ABORT: |
| 1367 | ret = COMPACT_CONTENDED; |
| 1368 | putback_movable_pages(&cc->migratepages); |
| 1369 | cc->nr_migratepages = 0; |
| 1370 | goto out; |
| 1371 | case ISOLATE_NONE: |
| 1372 | /* |
| 1373 | * We haven't isolated and migrated anything, but |
| 1374 | * there might still be unflushed migrations from |
| 1375 | * previous cc->order aligned block. |
| 1376 | */ |
| 1377 | goto check_drain; |
| 1378 | case ISOLATE_SUCCESS: |
| 1379 | ; |
| 1380 | } |
| 1381 | |
| 1382 | err = migrate_pages(&cc->migratepages, compaction_alloc, |
| 1383 | compaction_free, (unsigned long)cc, cc->mode, |
| 1384 | MR_COMPACTION); |
| 1385 | |
| 1386 | trace_mm_compaction_migratepages(cc->nr_migratepages, err, |
| 1387 | &cc->migratepages); |
| 1388 | |
| 1389 | /* All pages were either migrated or will be released */ |
| 1390 | cc->nr_migratepages = 0; |
| 1391 | if (err) { |
| 1392 | putback_movable_pages(&cc->migratepages); |
| 1393 | /* |
| 1394 | * migrate_pages() may return -ENOMEM when scanners meet |
| 1395 | * and we want compact_finished() to detect it |
| 1396 | */ |
| 1397 | if (err == -ENOMEM && !compact_scanners_met(cc)) { |
| 1398 | ret = COMPACT_CONTENDED; |
| 1399 | goto out; |
| 1400 | } |
| 1401 | } |
| 1402 | |
| 1403 | check_drain: |
| 1404 | /* |
| 1405 | * Has the migration scanner moved away from the previous |
| 1406 | * cc->order aligned block where we migrated from? If yes, |
| 1407 | * flush the pages that were freed, so that they can merge and |
| 1408 | * compact_finished() can detect immediately if allocation |
| 1409 | * would succeed. |
| 1410 | */ |
| 1411 | if (cc->order > 0 && cc->last_migrated_pfn) { |
| 1412 | int cpu; |
| 1413 | unsigned long current_block_start = |
| 1414 | cc->migrate_pfn & ~((1UL << cc->order) - 1); |
| 1415 | |
| 1416 | if (cc->last_migrated_pfn < current_block_start) { |
| 1417 | cpu = get_cpu(); |
| 1418 | lru_add_drain_cpu(cpu); |
| 1419 | drain_local_pages(zone); |
| 1420 | put_cpu(); |
| 1421 | /* No more flushing until we migrate again */ |
| 1422 | cc->last_migrated_pfn = 0; |
| 1423 | } |
| 1424 | } |
| 1425 | |
| 1426 | } |
| 1427 | |
| 1428 | out: |
| 1429 | /* |
| 1430 | * Release free pages and update where the free scanner should restart, |
| 1431 | * so we don't leave any returned pages behind in the next attempt. |
| 1432 | */ |
| 1433 | if (cc->nr_freepages > 0) { |
| 1434 | unsigned long free_pfn = release_freepages(&cc->freepages); |
| 1435 | |
| 1436 | cc->nr_freepages = 0; |
| 1437 | VM_BUG_ON(free_pfn == 0); |
| 1438 | /* The cached pfn is always the first in a pageblock */ |
| 1439 | free_pfn &= ~(pageblock_nr_pages-1); |
| 1440 | /* |
| 1441 | * Only go back, not forward. The cached pfn might have been |
| 1442 | * already reset to zone end in compact_finished() |
| 1443 | */ |
| 1444 | if (free_pfn > zone->compact_cached_free_pfn) |
| 1445 | zone->compact_cached_free_pfn = free_pfn; |
| 1446 | } |
| 1447 | |
| 1448 | trace_mm_compaction_end(start_pfn, cc->migrate_pfn, |
| 1449 | cc->free_pfn, end_pfn, sync, ret); |
| 1450 | |
| 1451 | if (ret == COMPACT_CONTENDED) |
| 1452 | ret = COMPACT_PARTIAL; |
| 1453 | |
| 1454 | return ret; |
| 1455 | } |
| 1456 | |
| 1457 | static unsigned long compact_zone_order(struct zone *zone, int order, |
| 1458 | gfp_t gfp_mask, enum migrate_mode mode, int *contended, |
| 1459 | int alloc_flags, int classzone_idx) |
| 1460 | { |
| 1461 | unsigned long ret; |
| 1462 | struct compact_control cc = { |
| 1463 | .nr_freepages = 0, |
| 1464 | .nr_migratepages = 0, |
| 1465 | .order = order, |
| 1466 | .gfp_mask = gfp_mask, |
| 1467 | .zone = zone, |
| 1468 | .mode = mode, |
| 1469 | .alloc_flags = alloc_flags, |
| 1470 | .classzone_idx = classzone_idx, |
| 1471 | .direct_compaction = true, |
| 1472 | }; |
| 1473 | INIT_LIST_HEAD(&cc.freepages); |
| 1474 | INIT_LIST_HEAD(&cc.migratepages); |
| 1475 | |
| 1476 | ret = compact_zone(zone, &cc); |
| 1477 | |
| 1478 | VM_BUG_ON(!list_empty(&cc.freepages)); |
| 1479 | VM_BUG_ON(!list_empty(&cc.migratepages)); |
| 1480 | |
| 1481 | *contended = cc.contended; |
| 1482 | return ret; |
| 1483 | } |
| 1484 | |
| 1485 | int sysctl_extfrag_threshold = 500; |
| 1486 | |
| 1487 | /** |
| 1488 | * try_to_compact_pages - Direct compact to satisfy a high-order allocation |
| 1489 | * @gfp_mask: The GFP mask of the current allocation |
| 1490 | * @order: The order of the current allocation |
| 1491 | * @alloc_flags: The allocation flags of the current allocation |
| 1492 | * @ac: The context of current allocation |
| 1493 | * @mode: The migration mode for async, sync light, or sync migration |
| 1494 | * @contended: Return value that determines if compaction was aborted due to |
| 1495 | * need_resched() or lock contention |
| 1496 | * |
| 1497 | * This is the main entry point for direct page compaction. |
| 1498 | */ |
| 1499 | unsigned long try_to_compact_pages(gfp_t gfp_mask, unsigned int order, |
| 1500 | int alloc_flags, const struct alloc_context *ac, |
| 1501 | enum migrate_mode mode, int *contended) |
| 1502 | { |
| 1503 | int may_enter_fs = gfp_mask & __GFP_FS; |
| 1504 | int may_perform_io = gfp_mask & __GFP_IO; |
| 1505 | struct zoneref *z; |
| 1506 | struct zone *zone; |
| 1507 | int rc = COMPACT_DEFERRED; |
| 1508 | int all_zones_contended = COMPACT_CONTENDED_LOCK; /* init for &= op */ |
| 1509 | |
| 1510 | *contended = COMPACT_CONTENDED_NONE; |
| 1511 | |
| 1512 | /* Check if the GFP flags allow compaction */ |
| 1513 | if (!order || !may_enter_fs || !may_perform_io) |
| 1514 | return COMPACT_SKIPPED; |
| 1515 | |
| 1516 | trace_mm_compaction_try_to_compact_pages(order, gfp_mask, mode); |
| 1517 | |
| 1518 | /* Compact each zone in the list */ |
| 1519 | for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx, |
| 1520 | ac->nodemask) { |
| 1521 | int status; |
| 1522 | int zone_contended; |
| 1523 | |
| 1524 | if (compaction_deferred(zone, order)) |
| 1525 | continue; |
| 1526 | |
| 1527 | status = compact_zone_order(zone, order, gfp_mask, mode, |
| 1528 | &zone_contended, alloc_flags, |
| 1529 | ac->classzone_idx); |
| 1530 | rc = max(status, rc); |
| 1531 | /* |
| 1532 | * It takes at least one zone that wasn't lock contended |
| 1533 | * to clear all_zones_contended. |
| 1534 | */ |
| 1535 | all_zones_contended &= zone_contended; |
| 1536 | |
| 1537 | /* If a normal allocation would succeed, stop compacting */ |
| 1538 | if (zone_watermark_ok(zone, order, low_wmark_pages(zone), |
| 1539 | ac->classzone_idx, alloc_flags)) { |
| 1540 | /* |
| 1541 | * We think the allocation will succeed in this zone, |
| 1542 | * but it is not certain, hence the false. The caller |
| 1543 | * will repeat this with true if allocation indeed |
| 1544 | * succeeds in this zone. |
| 1545 | */ |
| 1546 | compaction_defer_reset(zone, order, false); |
| 1547 | /* |
| 1548 | * It is possible that async compaction aborted due to |
| 1549 | * need_resched() and the watermarks were ok thanks to |
| 1550 | * somebody else freeing memory. The allocation can |
| 1551 | * however still fail so we better signal the |
| 1552 | * need_resched() contention anyway (this will not |
| 1553 | * prevent the allocation attempt). |
| 1554 | */ |
| 1555 | if (zone_contended == COMPACT_CONTENDED_SCHED) |
| 1556 | *contended = COMPACT_CONTENDED_SCHED; |
| 1557 | |
| 1558 | goto break_loop; |
| 1559 | } |
| 1560 | |
| 1561 | if (mode != MIGRATE_ASYNC && status == COMPACT_COMPLETE) { |
| 1562 | /* |
| 1563 | * We think that allocation won't succeed in this zone |
| 1564 | * so we defer compaction there. If it ends up |
| 1565 | * succeeding after all, it will be reset. |
| 1566 | */ |
| 1567 | defer_compaction(zone, order); |
| 1568 | } |
| 1569 | |
| 1570 | /* |
| 1571 | * We might have stopped compacting due to need_resched() in |
| 1572 | * async compaction, or due to a fatal signal detected. In that |
| 1573 | * case do not try further zones and signal need_resched() |
| 1574 | * contention. |
| 1575 | */ |
| 1576 | if ((zone_contended == COMPACT_CONTENDED_SCHED) |
| 1577 | || fatal_signal_pending(current)) { |
| 1578 | *contended = COMPACT_CONTENDED_SCHED; |
| 1579 | goto break_loop; |
| 1580 | } |
| 1581 | |
| 1582 | continue; |
| 1583 | break_loop: |
| 1584 | /* |
| 1585 | * We might not have tried all the zones, so be conservative |
| 1586 | * and assume they are not all lock contended. |
| 1587 | */ |
| 1588 | all_zones_contended = 0; |
| 1589 | break; |
| 1590 | } |
| 1591 | |
| 1592 | /* |
| 1593 | * If at least one zone wasn't deferred or skipped, we report if all |
| 1594 | * zones that were tried were lock contended. |
| 1595 | */ |
| 1596 | if (rc > COMPACT_SKIPPED && all_zones_contended) |
| 1597 | *contended = COMPACT_CONTENDED_LOCK; |
| 1598 | |
| 1599 | return rc; |
| 1600 | } |
| 1601 | |
| 1602 | |
| 1603 | /* Compact all zones within a node */ |
| 1604 | static void __compact_pgdat(pg_data_t *pgdat, struct compact_control *cc) |
| 1605 | { |
| 1606 | int zoneid; |
| 1607 | struct zone *zone; |
| 1608 | |
| 1609 | for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) { |
| 1610 | |
| 1611 | zone = &pgdat->node_zones[zoneid]; |
| 1612 | if (!populated_zone(zone)) |
| 1613 | continue; |
| 1614 | |
| 1615 | cc->nr_freepages = 0; |
| 1616 | cc->nr_migratepages = 0; |
| 1617 | cc->zone = zone; |
| 1618 | INIT_LIST_HEAD(&cc->freepages); |
| 1619 | INIT_LIST_HEAD(&cc->migratepages); |
| 1620 | |
| 1621 | /* |
| 1622 | * When called via /proc/sys/vm/compact_memory |
| 1623 | * this makes sure we compact the whole zone regardless of |
| 1624 | * cached scanner positions. |
| 1625 | */ |
| 1626 | if (is_via_compact_memory(cc->order)) |
| 1627 | __reset_isolation_suitable(zone); |
| 1628 | |
| 1629 | if (is_via_compact_memory(cc->order) || |
| 1630 | !compaction_deferred(zone, cc->order)) |
| 1631 | compact_zone(zone, cc); |
| 1632 | |
| 1633 | VM_BUG_ON(!list_empty(&cc->freepages)); |
| 1634 | VM_BUG_ON(!list_empty(&cc->migratepages)); |
| 1635 | |
| 1636 | if (is_via_compact_memory(cc->order)) |
| 1637 | continue; |
| 1638 | |
| 1639 | if (zone_watermark_ok(zone, cc->order, |
| 1640 | low_wmark_pages(zone), 0, 0)) |
| 1641 | compaction_defer_reset(zone, cc->order, false); |
| 1642 | } |
| 1643 | } |
| 1644 | |
| 1645 | void compact_pgdat(pg_data_t *pgdat, int order) |
| 1646 | { |
| 1647 | struct compact_control cc = { |
| 1648 | .order = order, |
| 1649 | .mode = MIGRATE_ASYNC, |
| 1650 | }; |
| 1651 | |
| 1652 | if (!order) |
| 1653 | return; |
| 1654 | |
| 1655 | __compact_pgdat(pgdat, &cc); |
| 1656 | } |
| 1657 | |
| 1658 | static void compact_node(int nid) |
| 1659 | { |
| 1660 | struct compact_control cc = { |
| 1661 | .order = -1, |
| 1662 | .mode = MIGRATE_SYNC, |
| 1663 | .ignore_skip_hint = true, |
| 1664 | }; |
| 1665 | |
| 1666 | __compact_pgdat(NODE_DATA(nid), &cc); |
| 1667 | } |
| 1668 | |
| 1669 | /* Compact all nodes in the system */ |
| 1670 | static void compact_nodes(void) |
| 1671 | { |
| 1672 | int nid; |
| 1673 | |
| 1674 | /* Flush pending updates to the LRU lists */ |
| 1675 | lru_add_drain_all(); |
| 1676 | |
| 1677 | for_each_online_node(nid) |
| 1678 | compact_node(nid); |
| 1679 | } |
| 1680 | |
| 1681 | /* The written value is actually unused, all memory is compacted */ |
| 1682 | int sysctl_compact_memory; |
| 1683 | |
| 1684 | /* |
| 1685 | * This is the entry point for compacting all nodes via |
| 1686 | * /proc/sys/vm/compact_memory |
| 1687 | */ |
| 1688 | int sysctl_compaction_handler(struct ctl_table *table, int write, |
| 1689 | void __user *buffer, size_t *length, loff_t *ppos) |
| 1690 | { |
| 1691 | if (write) |
| 1692 | compact_nodes(); |
| 1693 | |
| 1694 | return 0; |
| 1695 | } |
| 1696 | |
| 1697 | int sysctl_extfrag_handler(struct ctl_table *table, int write, |
| 1698 | void __user *buffer, size_t *length, loff_t *ppos) |
| 1699 | { |
| 1700 | proc_dointvec_minmax(table, write, buffer, length, ppos); |
| 1701 | |
| 1702 | return 0; |
| 1703 | } |
| 1704 | |
| 1705 | #if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA) |
| 1706 | static ssize_t sysfs_compact_node(struct device *dev, |
| 1707 | struct device_attribute *attr, |
| 1708 | const char *buf, size_t count) |
| 1709 | { |
| 1710 | int nid = dev->id; |
| 1711 | |
| 1712 | if (nid >= 0 && nid < nr_node_ids && node_online(nid)) { |
| 1713 | /* Flush pending updates to the LRU lists */ |
| 1714 | lru_add_drain_all(); |
| 1715 | |
| 1716 | compact_node(nid); |
| 1717 | } |
| 1718 | |
| 1719 | return count; |
| 1720 | } |
| 1721 | static DEVICE_ATTR(compact, S_IWUSR, NULL, sysfs_compact_node); |
| 1722 | |
| 1723 | int compaction_register_node(struct node *node) |
| 1724 | { |
| 1725 | return device_create_file(&node->dev, &dev_attr_compact); |
| 1726 | } |
| 1727 | |
| 1728 | void compaction_unregister_node(struct node *node) |
| 1729 | { |
| 1730 | return device_remove_file(&node->dev, &dev_attr_compact); |
| 1731 | } |
| 1732 | #endif /* CONFIG_SYSFS && CONFIG_NUMA */ |
| 1733 | |
| 1734 | static inline bool kcompactd_work_requested(pg_data_t *pgdat) |
| 1735 | { |
| 1736 | return pgdat->kcompactd_max_order > 0 || kthread_should_stop(); |
| 1737 | } |
| 1738 | |
| 1739 | static bool kcompactd_node_suitable(pg_data_t *pgdat) |
| 1740 | { |
| 1741 | int zoneid; |
| 1742 | struct zone *zone; |
| 1743 | enum zone_type classzone_idx = pgdat->kcompactd_classzone_idx; |
| 1744 | |
| 1745 | for (zoneid = 0; zoneid < classzone_idx; zoneid++) { |
| 1746 | zone = &pgdat->node_zones[zoneid]; |
| 1747 | |
| 1748 | if (!populated_zone(zone)) |
| 1749 | continue; |
| 1750 | |
| 1751 | if (compaction_suitable(zone, pgdat->kcompactd_max_order, 0, |
| 1752 | classzone_idx) == COMPACT_CONTINUE) |
| 1753 | return true; |
| 1754 | } |
| 1755 | |
| 1756 | return false; |
| 1757 | } |
| 1758 | |
| 1759 | static void kcompactd_do_work(pg_data_t *pgdat) |
| 1760 | { |
| 1761 | /* |
| 1762 | * With no special task, compact all zones so that a page of requested |
| 1763 | * order is allocatable. |
| 1764 | */ |
| 1765 | int zoneid; |
| 1766 | struct zone *zone; |
| 1767 | struct compact_control cc = { |
| 1768 | .order = pgdat->kcompactd_max_order, |
| 1769 | .classzone_idx = pgdat->kcompactd_classzone_idx, |
| 1770 | .mode = MIGRATE_SYNC_LIGHT, |
| 1771 | .ignore_skip_hint = true, |
| 1772 | |
| 1773 | }; |
| 1774 | bool success = false; |
| 1775 | |
| 1776 | trace_mm_compaction_kcompactd_wake(pgdat->node_id, cc.order, |
| 1777 | cc.classzone_idx); |
| 1778 | count_vm_event(KCOMPACTD_WAKE); |
| 1779 | |
| 1780 | for (zoneid = 0; zoneid < cc.classzone_idx; zoneid++) { |
| 1781 | int status; |
| 1782 | |
| 1783 | zone = &pgdat->node_zones[zoneid]; |
| 1784 | if (!populated_zone(zone)) |
| 1785 | continue; |
| 1786 | |
| 1787 | if (compaction_deferred(zone, cc.order)) |
| 1788 | continue; |
| 1789 | |
| 1790 | if (compaction_suitable(zone, cc.order, 0, zoneid) != |
| 1791 | COMPACT_CONTINUE) |
| 1792 | continue; |
| 1793 | |
| 1794 | cc.nr_freepages = 0; |
| 1795 | cc.nr_migratepages = 0; |
| 1796 | cc.zone = zone; |
| 1797 | INIT_LIST_HEAD(&cc.freepages); |
| 1798 | INIT_LIST_HEAD(&cc.migratepages); |
| 1799 | |
| 1800 | if (kthread_should_stop()) |
| 1801 | return; |
| 1802 | status = compact_zone(zone, &cc); |
| 1803 | |
| 1804 | if (zone_watermark_ok(zone, cc.order, low_wmark_pages(zone), |
| 1805 | cc.classzone_idx, 0)) { |
| 1806 | success = true; |
| 1807 | compaction_defer_reset(zone, cc.order, false); |
| 1808 | } else if (status == COMPACT_COMPLETE) { |
| 1809 | /* |
| 1810 | * We use sync migration mode here, so we defer like |
| 1811 | * sync direct compaction does. |
| 1812 | */ |
| 1813 | defer_compaction(zone, cc.order); |
| 1814 | } |
| 1815 | |
| 1816 | VM_BUG_ON(!list_empty(&cc.freepages)); |
| 1817 | VM_BUG_ON(!list_empty(&cc.migratepages)); |
| 1818 | } |
| 1819 | |
| 1820 | /* |
| 1821 | * Regardless of success, we are done until woken up next. But remember |
| 1822 | * the requested order/classzone_idx in case it was higher/tighter than |
| 1823 | * our current ones |
| 1824 | */ |
| 1825 | if (pgdat->kcompactd_max_order <= cc.order) |
| 1826 | pgdat->kcompactd_max_order = 0; |
| 1827 | if (pgdat->kcompactd_classzone_idx >= cc.classzone_idx) |
| 1828 | pgdat->kcompactd_classzone_idx = pgdat->nr_zones - 1; |
| 1829 | } |
| 1830 | |
| 1831 | void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx) |
| 1832 | { |
| 1833 | if (!order) |
| 1834 | return; |
| 1835 | |
| 1836 | if (pgdat->kcompactd_max_order < order) |
| 1837 | pgdat->kcompactd_max_order = order; |
| 1838 | |
| 1839 | if (pgdat->kcompactd_classzone_idx > classzone_idx) |
| 1840 | pgdat->kcompactd_classzone_idx = classzone_idx; |
| 1841 | |
| 1842 | if (!waitqueue_active(&pgdat->kcompactd_wait)) |
| 1843 | return; |
| 1844 | |
| 1845 | if (!kcompactd_node_suitable(pgdat)) |
| 1846 | return; |
| 1847 | |
| 1848 | trace_mm_compaction_wakeup_kcompactd(pgdat->node_id, order, |
| 1849 | classzone_idx); |
| 1850 | wake_up_interruptible(&pgdat->kcompactd_wait); |
| 1851 | } |
| 1852 | |
| 1853 | /* |
| 1854 | * The background compaction daemon, started as a kernel thread |
| 1855 | * from the init process. |
| 1856 | */ |
| 1857 | static int kcompactd(void *p) |
| 1858 | { |
| 1859 | pg_data_t *pgdat = (pg_data_t*)p; |
| 1860 | struct task_struct *tsk = current; |
| 1861 | |
| 1862 | const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id); |
| 1863 | |
| 1864 | if (!cpumask_empty(cpumask)) |
| 1865 | set_cpus_allowed_ptr(tsk, cpumask); |
| 1866 | |
| 1867 | set_freezable(); |
| 1868 | |
| 1869 | pgdat->kcompactd_max_order = 0; |
| 1870 | pgdat->kcompactd_classzone_idx = pgdat->nr_zones - 1; |
| 1871 | |
| 1872 | while (!kthread_should_stop()) { |
| 1873 | trace_mm_compaction_kcompactd_sleep(pgdat->node_id); |
| 1874 | wait_event_freezable(pgdat->kcompactd_wait, |
| 1875 | kcompactd_work_requested(pgdat)); |
| 1876 | |
| 1877 | kcompactd_do_work(pgdat); |
| 1878 | } |
| 1879 | |
| 1880 | return 0; |
| 1881 | } |
| 1882 | |
| 1883 | /* |
| 1884 | * This kcompactd start function will be called by init and node-hot-add. |
| 1885 | * On node-hot-add, kcompactd will moved to proper cpus if cpus are hot-added. |
| 1886 | */ |
| 1887 | int kcompactd_run(int nid) |
| 1888 | { |
| 1889 | pg_data_t *pgdat = NODE_DATA(nid); |
| 1890 | int ret = 0; |
| 1891 | |
| 1892 | if (pgdat->kcompactd) |
| 1893 | return 0; |
| 1894 | |
| 1895 | pgdat->kcompactd = kthread_run(kcompactd, pgdat, "kcompactd%d", nid); |
| 1896 | if (IS_ERR(pgdat->kcompactd)) { |
| 1897 | pr_err("Failed to start kcompactd on node %d\n", nid); |
| 1898 | ret = PTR_ERR(pgdat->kcompactd); |
| 1899 | pgdat->kcompactd = NULL; |
| 1900 | } |
| 1901 | return ret; |
| 1902 | } |
| 1903 | |
| 1904 | /* |
| 1905 | * Called by memory hotplug when all memory in a node is offlined. Caller must |
| 1906 | * hold mem_hotplug_begin/end(). |
| 1907 | */ |
| 1908 | void kcompactd_stop(int nid) |
| 1909 | { |
| 1910 | struct task_struct *kcompactd = NODE_DATA(nid)->kcompactd; |
| 1911 | |
| 1912 | if (kcompactd) { |
| 1913 | kthread_stop(kcompactd); |
| 1914 | NODE_DATA(nid)->kcompactd = NULL; |
| 1915 | } |
| 1916 | } |
| 1917 | |
| 1918 | /* |
| 1919 | * It's optimal to keep kcompactd on the same CPUs as their memory, but |
| 1920 | * not required for correctness. So if the last cpu in a node goes |
| 1921 | * away, we get changed to run anywhere: as the first one comes back, |
| 1922 | * restore their cpu bindings. |
| 1923 | */ |
| 1924 | static int cpu_callback(struct notifier_block *nfb, unsigned long action, |
| 1925 | void *hcpu) |
| 1926 | { |
| 1927 | int nid; |
| 1928 | |
| 1929 | if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) { |
| 1930 | for_each_node_state(nid, N_MEMORY) { |
| 1931 | pg_data_t *pgdat = NODE_DATA(nid); |
| 1932 | const struct cpumask *mask; |
| 1933 | |
| 1934 | mask = cpumask_of_node(pgdat->node_id); |
| 1935 | |
| 1936 | if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids) |
| 1937 | /* One of our CPUs online: restore mask */ |
| 1938 | set_cpus_allowed_ptr(pgdat->kcompactd, mask); |
| 1939 | } |
| 1940 | } |
| 1941 | return NOTIFY_OK; |
| 1942 | } |
| 1943 | |
| 1944 | static int __init kcompactd_init(void) |
| 1945 | { |
| 1946 | int nid; |
| 1947 | |
| 1948 | for_each_node_state(nid, N_MEMORY) |
| 1949 | kcompactd_run(nid); |
| 1950 | hotcpu_notifier(cpu_callback, 0); |
| 1951 | return 0; |
| 1952 | } |
| 1953 | subsys_initcall(kcompactd_init) |
| 1954 | |
| 1955 | #endif /* CONFIG_COMPACTION */ |