1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _BCACHEFS_BSET_H
3 #define _BCACHEFS_BSET_H
5 #include <linux/kernel.h>
6 #include <linux/types.h>
10 #include "bkey_methods.h"
11 #include "btree_types.h"
12 #include "util.h" /* for time_stats */
18 * A bkey contains a key, a size field, a variable number of pointers, and some
19 * ancillary flag bits.
21 * We use two different functions for validating bkeys, bkey_invalid and
24 * The one exception to the rule that ptr_invalid() filters out invalid keys is
25 * that it also filters out keys of size 0 - these are keys that have been
26 * completely overwritten. It'd be safe to delete these in memory while leaving
27 * them on disk, just unnecessary work - so we filter them out when resorting
30 * We can't filter out stale keys when we're resorting, because garbage
31 * collection needs to find them to ensure bucket gens don't wrap around -
32 * unless we're rewriting the btree node those stale keys still exist on disk.
34 * We also implement functions here for removing some number of sectors from the
35 * front or the back of a bkey - this is mainly used for fixing overlapping
36 * extents, by removing the overlapping sectors from the older key.
40 * A bset is an array of bkeys laid out contiguously in memory in sorted order,
41 * along with a header. A btree node is made up of a number of these, written at
44 * There could be many of them on disk, but we never allow there to be more than
45 * 4 in memory - we lazily resort as needed.
47 * We implement code here for creating and maintaining auxiliary search trees
48 * (described below) for searching an individial bset, and on top of that we
49 * implement a btree iterator.
53 * Most of the code in bcache doesn't care about an individual bset - it needs
54 * to search entire btree nodes and iterate over them in sorted order.
56 * The btree iterator code serves both functions; it iterates through the keys
57 * in a btree node in sorted order, starting from either keys after a specific
58 * point (if you pass it a search key) or the start of the btree node.
60 * AUXILIARY SEARCH TREES:
62 * Since keys are variable length, we can't use a binary search on a bset - we
63 * wouldn't be able to find the start of the next key. But binary searches are
64 * slow anyways, due to terrible cache behaviour; bcache originally used binary
65 * searches and that code topped out at under 50k lookups/second.
67 * So we need to construct some sort of lookup table. Since we only insert keys
68 * into the last (unwritten) set, most of the keys within a given btree node are
69 * usually in sets that are mostly constant. We use two different types of
70 * lookup tables to take advantage of this.
72 * Both lookup tables share in common that they don't index every key in the
73 * set; they index one key every BSET_CACHELINE bytes, and then a linear search
74 * is used for the rest.
76 * For sets that have been written to disk and are no longer being inserted
77 * into, we construct a binary search tree in an array - traversing a binary
78 * search tree in an array gives excellent locality of reference and is very
79 * fast, since both children of any node are adjacent to each other in memory
80 * (and their grandchildren, and great grandchildren...) - this means
81 * prefetching can be used to great effect.
83 * It's quite useful performance wise to keep these nodes small - not just
84 * because they're more likely to be in L2, but also because we can prefetch
85 * more nodes on a single cacheline and thus prefetch more iterations in advance
86 * when traversing this tree.
88 * Nodes in the auxiliary search tree must contain both a key to compare against
89 * (we don't want to fetch the key from the set, that would defeat the purpose),
90 * and a pointer to the key. We use a few tricks to compress both of these.
92 * To compress the pointer, we take advantage of the fact that one node in the
93 * search tree corresponds to precisely BSET_CACHELINE bytes in the set. We have
94 * a function (to_inorder()) that takes the index of a node in a binary tree and
95 * returns what its index would be in an inorder traversal, so we only have to
96 * store the low bits of the offset.
98 * The key is 84 bits (KEY_DEV + key->key, the offset on the device). To
99 * compress that, we take advantage of the fact that when we're traversing the
100 * search tree at every iteration we know that both our search key and the key
101 * we're looking for lie within some range - bounded by our previous
102 * comparisons. (We special case the start of a search so that this is true even
103 * at the root of the tree).
105 * So we know the key we're looking for is between a and b, and a and b don't
106 * differ higher than bit 50, we don't need to check anything higher than bit
109 * We don't usually need the rest of the bits, either; we only need enough bits
110 * to partition the key range we're currently checking. Consider key n - the
111 * key our auxiliary search tree node corresponds to, and key p, the key
112 * immediately preceding n. The lowest bit we need to store in the auxiliary
113 * search tree is the highest bit that differs between n and p.
115 * Note that this could be bit 0 - we might sometimes need all 80 bits to do the
116 * comparison. But we'd really like our nodes in the auxiliary search tree to be
119 * The solution is to make them fixed size, and when we're constructing a node
120 * check if p and n differed in the bits we needed them to. If they don't we
121 * flag that node, and when doing lookups we fallback to comparing against the
122 * real key. As long as this doesn't happen to often (and it seems to reliably
123 * happen a bit less than 1% of the time), we win - even on failures, that key
124 * is then more likely to be in cache than if we were doing binary searches all
125 * the way, since we're touching so much less memory.
127 * The keys in the auxiliary search tree are stored in (software) floating
128 * point, with an exponent and a mantissa. The exponent needs to be big enough
129 * to address all the bits in the original key, but the number of bits in the
130 * mantissa is somewhat arbitrary; more bits just gets us fewer failures.
132 * We need 7 bits for the exponent and 3 bits for the key's offset (since keys
133 * are 8 byte aligned); using 22 bits for the mantissa means a node is 4 bytes.
134 * We need one node per 128 bytes in the btree node, which means the auxiliary
135 * search trees take up 3% as much memory as the btree itself.
137 * Constructing these auxiliary search trees is moderately expensive, and we
138 * don't want to be constantly rebuilding the search tree for the last set
139 * whenever we insert another key into it. For the unwritten set, we use a much
140 * simpler lookup table - it's just a flat array, so index i in the lookup table
141 * corresponds to the i range of BSET_CACHELINE bytes in the set. Indexing
142 * within each byte range works the same as with the auxiliary search trees.
144 * These are much easier to keep up to date when we insert a key - we do it
145 * somewhat lazily; when we shift a key up we usually just increment the pointer
146 * to it, only when it would overflow do we go to the trouble of finding the
147 * first key in that range of bytes again.
150 enum bset_aux_tree_type {
156 #define BSET_TREE_NR_TYPES 3
158 #define BSET_NO_AUX_TREE_VAL (U16_MAX)
159 #define BSET_RW_AUX_TREE_VAL (U16_MAX - 1)
161 static inline enum bset_aux_tree_type bset_aux_tree_type(const struct bset_tree *t)
164 case BSET_NO_AUX_TREE_VAL:
166 return BSET_NO_AUX_TREE;
167 case BSET_RW_AUX_TREE_VAL:
169 return BSET_RW_AUX_TREE;
172 return BSET_RO_AUX_TREE;
177 * BSET_CACHELINE was originally intended to match the hardware cacheline size -
178 * it used to be 64, but I realized the lookup code would touch slightly less
179 * memory if it was 128.
181 * It definites the number of bytes (in struct bset) per struct bkey_float in
182 * the auxiliar search tree - when we're done searching the bset_float tree we
183 * have this many bytes left that we do a linear search over.
185 * Since (after level 5) every level of the bset_tree is on a new cacheline,
186 * we're touching one fewer cacheline in the bset tree in exchange for one more
187 * cacheline in the linear search - but the linear search might stop before it
188 * gets to the second cacheline.
191 #define BSET_CACHELINE 128
193 static inline size_t btree_keys_cachelines(const struct btree *b)
195 return (1U << b->byte_order) / BSET_CACHELINE;
198 static inline size_t btree_aux_data_bytes(const struct btree *b)
200 return btree_keys_cachelines(b) * 8;
203 static inline size_t btree_aux_data_u64s(const struct btree *b)
205 return btree_aux_data_bytes(b) / sizeof(u64);
208 typedef void (*compiled_unpack_fn)(struct bkey *, const struct bkey_packed *);
211 __bkey_unpack_key_format_checked(const struct btree *b,
213 const struct bkey_packed *src)
215 #ifdef HAVE_BCACHEFS_COMPILED_UNPACK
217 compiled_unpack_fn unpack_fn = b->aux_data;
220 if (bch2_expensive_debug_checks) {
221 struct bkey dst2 = __bch2_bkey_unpack_key(&b->format, src);
223 BUG_ON(memcmp(dst, &dst2, sizeof(*dst)));
227 *dst = __bch2_bkey_unpack_key(&b->format, src);
231 static inline struct bkey
232 bkey_unpack_key_format_checked(const struct btree *b,
233 const struct bkey_packed *src)
237 __bkey_unpack_key_format_checked(b, &dst, src);
241 static inline void __bkey_unpack_key(const struct btree *b,
243 const struct bkey_packed *src)
245 if (likely(bkey_packed(src)))
246 __bkey_unpack_key_format_checked(b, dst, src);
248 *dst = *packed_to_bkey_c(src);
252 * bkey_unpack_key -- unpack just the key, not the value
254 static inline struct bkey bkey_unpack_key(const struct btree *b,
255 const struct bkey_packed *src)
257 return likely(bkey_packed(src))
258 ? bkey_unpack_key_format_checked(b, src)
259 : *packed_to_bkey_c(src);
262 static inline struct bpos
263 bkey_unpack_pos_format_checked(const struct btree *b,
264 const struct bkey_packed *src)
266 #ifdef HAVE_BCACHEFS_COMPILED_UNPACK
267 return bkey_unpack_key_format_checked(b, src).p;
269 return __bkey_unpack_pos(&b->format, src);
273 static inline struct bpos bkey_unpack_pos(const struct btree *b,
274 const struct bkey_packed *src)
276 return likely(bkey_packed(src))
277 ? bkey_unpack_pos_format_checked(b, src)
278 : packed_to_bkey_c(src)->p;
281 /* Disassembled bkeys */
283 static inline struct bkey_s_c bkey_disassemble(struct btree *b,
284 const struct bkey_packed *k,
287 __bkey_unpack_key(b, u, k);
289 return (struct bkey_s_c) { u, bkeyp_val(&b->format, k), };
292 /* non const version: */
293 static inline struct bkey_s __bkey_disassemble(struct btree *b,
294 struct bkey_packed *k,
297 __bkey_unpack_key(b, u, k);
299 return (struct bkey_s) { .k = u, .v = bkeyp_val(&b->format, k), };
302 #define for_each_bset(_b, _t) \
303 for (_t = (_b)->set; _t < (_b)->set + (_b)->nsets; _t++)
305 #define bset_tree_for_each_key(_b, _t, _k) \
306 for (_k = btree_bkey_first(_b, _t); \
307 _k != btree_bkey_last(_b, _t); \
308 _k = bkey_next_skip_noops(_k, btree_bkey_last(_b, _t)))
310 static inline bool bset_has_ro_aux_tree(struct bset_tree *t)
312 return bset_aux_tree_type(t) == BSET_RO_AUX_TREE;
315 static inline bool bset_has_rw_aux_tree(struct bset_tree *t)
317 return bset_aux_tree_type(t) == BSET_RW_AUX_TREE;
320 static inline void bch2_bset_set_no_aux_tree(struct btree *b,
325 for (; t < b->set + ARRAY_SIZE(b->set); t++) {
327 t->extra = BSET_NO_AUX_TREE_VAL;
328 t->aux_data_offset = U16_MAX;
332 static inline void btree_node_set_format(struct btree *b,
333 struct bkey_format f)
338 b->nr_key_bits = bkey_format_key_bits(&f);
340 len = bch2_compile_bkey_format(&b->format, b->aux_data);
341 BUG_ON(len < 0 || len > U8_MAX);
343 b->unpack_fn_len = len;
345 bch2_bset_set_no_aux_tree(b, b->set);
348 static inline struct bset *bset_next_set(struct btree *b,
349 unsigned block_bytes)
351 struct bset *i = btree_bset_last(b);
353 EBUG_ON(!is_power_of_2(block_bytes));
355 return ((void *) i) + round_up(vstruct_bytes(i), block_bytes);
358 void bch2_btree_keys_init(struct btree *);
360 void bch2_bset_init_first(struct btree *, struct bset *);
361 void bch2_bset_init_next(struct bch_fs *, struct btree *,
362 struct btree_node_entry *);
363 void bch2_bset_build_aux_tree(struct btree *, struct bset_tree *, bool);
364 void bch2_bset_fix_invalidated_key(struct btree *, struct bkey_packed *);
366 void bch2_bset_insert(struct btree *, struct btree_node_iter *,
367 struct bkey_packed *, struct bkey_i *, unsigned);
368 void bch2_bset_delete(struct btree *, struct bkey_packed *, unsigned);
370 /* Bkey utility code */
372 /* packed or unpacked */
373 static inline int bkey_cmp_p_or_unp(const struct btree *b,
374 const struct bkey_packed *l,
375 const struct bkey_packed *r_packed,
376 const struct bpos *r)
378 EBUG_ON(r_packed && !bkey_packed(r_packed));
380 if (unlikely(!bkey_packed(l)))
381 return bkey_cmp(packed_to_bkey_c(l)->p, *r);
383 if (likely(r_packed))
384 return __bch2_bkey_cmp_packed_format_checked(l, r_packed, b);
386 return __bch2_bkey_cmp_left_packed_format_checked(b, l, r);
389 static inline struct bset_tree *
390 bch2_bkey_to_bset_inlined(struct btree *b, struct bkey_packed *k)
392 unsigned offset = __btree_node_key_to_offset(b, k);
396 if (offset <= t->end_offset) {
397 EBUG_ON(offset < btree_bkey_first_offset(t));
404 struct bset_tree *bch2_bkey_to_bset(struct btree *, struct bkey_packed *);
406 struct bkey_packed *bch2_bkey_prev_filter(struct btree *, struct bset_tree *,
407 struct bkey_packed *, unsigned);
409 static inline struct bkey_packed *
410 bch2_bkey_prev_all(struct btree *b, struct bset_tree *t, struct bkey_packed *k)
412 return bch2_bkey_prev_filter(b, t, k, 0);
415 static inline struct bkey_packed *
416 bch2_bkey_prev(struct btree *b, struct bset_tree *t, struct bkey_packed *k)
418 return bch2_bkey_prev_filter(b, t, k, 1);
421 enum bch_extent_overlap {
422 BCH_EXTENT_OVERLAP_ALL = 0,
423 BCH_EXTENT_OVERLAP_BACK = 1,
424 BCH_EXTENT_OVERLAP_FRONT = 2,
425 BCH_EXTENT_OVERLAP_MIDDLE = 3,
428 /* Returns how k overlaps with m */
429 static inline enum bch_extent_overlap bch2_extent_overlap(const struct bkey *k,
430 const struct bkey *m)
432 int cmp1 = bkey_cmp(k->p, m->p) < 0;
433 int cmp2 = bkey_cmp(bkey_start_pos(k),
434 bkey_start_pos(m)) > 0;
436 return (cmp1 << 1) + cmp2;
439 /* Btree key iteration */
441 void bch2_btree_node_iter_push(struct btree_node_iter *, struct btree *,
442 const struct bkey_packed *,
443 const struct bkey_packed *);
444 void bch2_btree_node_iter_init(struct btree_node_iter *, struct btree *,
446 void bch2_btree_node_iter_init_from_start(struct btree_node_iter *,
448 struct bkey_packed *bch2_btree_node_iter_bset_pos(struct btree_node_iter *,
452 void bch2_btree_node_iter_sort(struct btree_node_iter *, struct btree *);
453 void bch2_btree_node_iter_set_drop(struct btree_node_iter *,
454 struct btree_node_iter_set *);
455 void bch2_btree_node_iter_advance(struct btree_node_iter *, struct btree *);
457 #define btree_node_iter_for_each(_iter, _set) \
458 for (_set = (_iter)->data; \
459 _set < (_iter)->data + ARRAY_SIZE((_iter)->data) && \
460 (_set)->k != (_set)->end; \
463 static inline bool __btree_node_iter_set_end(struct btree_node_iter *iter,
466 return iter->data[i].k == iter->data[i].end;
469 static inline bool bch2_btree_node_iter_end(struct btree_node_iter *iter)
471 return __btree_node_iter_set_end(iter, 0);
475 * When keys compare equal, deleted keys compare first:
477 * XXX: only need to compare pointers for keys that are both within a
478 * btree_node_iterator - we need to break ties for prev() to work correctly
480 static inline int bkey_iter_cmp(const struct btree *b,
481 const struct bkey_packed *l,
482 const struct bkey_packed *r)
484 return bch2_bkey_cmp_packed(b, l, r)
485 ?: (int) bkey_deleted(r) - (int) bkey_deleted(l)
489 static inline int btree_node_iter_cmp(const struct btree *b,
490 struct btree_node_iter_set l,
491 struct btree_node_iter_set r)
493 return bkey_iter_cmp(b,
494 __btree_node_offset_to_key(b, l.k),
495 __btree_node_offset_to_key(b, r.k));
498 /* These assume r (the search key) is not a deleted key: */
499 static inline int bkey_iter_pos_cmp(const struct btree *b,
500 const struct bkey_packed *l,
501 const struct bpos *r)
503 return bkey_cmp_left_packed(b, l, r)
504 ?: -((int) bkey_deleted(l));
507 static inline int bkey_iter_cmp_p_or_unp(const struct btree *b,
508 const struct bkey_packed *l,
509 const struct bkey_packed *r_packed,
510 const struct bpos *r)
512 return bkey_cmp_p_or_unp(b, l, r_packed, r)
513 ?: -((int) bkey_deleted(l));
516 static inline struct bkey_packed *
517 __bch2_btree_node_iter_peek_all(struct btree_node_iter *iter,
520 return __btree_node_offset_to_key(b, iter->data->k);
523 static inline struct bkey_packed *
524 bch2_btree_node_iter_peek_all(struct btree_node_iter *iter, struct btree *b)
526 return !bch2_btree_node_iter_end(iter)
527 ? __btree_node_offset_to_key(b, iter->data->k)
531 static inline struct bkey_packed *
532 bch2_btree_node_iter_peek(struct btree_node_iter *iter, struct btree *b)
534 struct bkey_packed *k;
536 while ((k = bch2_btree_node_iter_peek_all(iter, b)) &&
538 bch2_btree_node_iter_advance(iter, b);
543 static inline struct bkey_packed *
544 bch2_btree_node_iter_next_all(struct btree_node_iter *iter, struct btree *b)
546 struct bkey_packed *ret = bch2_btree_node_iter_peek_all(iter, b);
549 bch2_btree_node_iter_advance(iter, b);
554 struct bkey_packed *bch2_btree_node_iter_prev_all(struct btree_node_iter *,
556 struct bkey_packed *bch2_btree_node_iter_prev(struct btree_node_iter *,
559 struct bkey_s_c bch2_btree_node_iter_peek_unpack(struct btree_node_iter *,
563 #define for_each_btree_node_key_unpack(b, k, iter, unpacked) \
564 for (bch2_btree_node_iter_init_from_start((iter), (b)); \
565 (k = bch2_btree_node_iter_peek_unpack((iter), (b), (unpacked))).k;\
566 bch2_btree_node_iter_advance(iter, b))
570 static inline void btree_keys_account_key(struct btree_nr_keys *n,
572 struct bkey_packed *k,
575 n->live_u64s += k->u64s * sign;
576 n->bset_u64s[bset] += k->u64s * sign;
579 n->packed_keys += sign;
581 n->unpacked_keys += sign;
584 static inline void btree_keys_account_val_delta(struct btree *b,
585 struct bkey_packed *k,
588 struct bset_tree *t = bch2_bkey_to_bset(b, k);
590 b->nr.live_u64s += delta;
591 b->nr.bset_u64s[t - b->set] += delta;
594 #define btree_keys_account_key_add(_nr, _bset_idx, _k) \
595 btree_keys_account_key(_nr, _bset_idx, _k, 1)
596 #define btree_keys_account_key_drop(_nr, _bset_idx, _k) \
597 btree_keys_account_key(_nr, _bset_idx, _k, -1)
599 #define btree_account_key_add(_b, _k) \
600 btree_keys_account_key(&(_b)->nr, \
601 bch2_bkey_to_bset(_b, _k) - (_b)->set, _k, 1)
602 #define btree_account_key_drop(_b, _k) \
603 btree_keys_account_key(&(_b)->nr, \
604 bch2_bkey_to_bset(_b, _k) - (_b)->set, _k, -1)
609 } sets[BSET_TREE_NR_TYPES];
615 void bch2_btree_keys_stats(struct btree *, struct bset_stats *);
616 void bch2_bfloat_to_text(struct printbuf *, struct btree *,
617 struct bkey_packed *);
621 void bch2_dump_bset(struct bch_fs *, struct btree *, struct bset *, unsigned);
622 void bch2_dump_btree_node(struct bch_fs *, struct btree *);
623 void bch2_dump_btree_node_iter(struct btree *, struct btree_node_iter *);
625 #ifdef CONFIG_BCACHEFS_DEBUG
627 void __bch2_verify_btree_nr_keys(struct btree *);
628 void bch2_btree_node_iter_verify(struct btree_node_iter *, struct btree *);
629 void bch2_verify_insert_pos(struct btree *, struct bkey_packed *,
630 struct bkey_packed *, unsigned);
634 static inline void __bch2_verify_btree_nr_keys(struct btree *b) {}
635 static inline void bch2_btree_node_iter_verify(struct btree_node_iter *iter,
637 static inline void bch2_verify_insert_pos(struct btree *b,
638 struct bkey_packed *where,
639 struct bkey_packed *insert,
640 unsigned clobber_u64s) {}
643 static inline void bch2_verify_btree_nr_keys(struct btree *b)
645 if (bch2_debug_check_btree_accounting)
646 __bch2_verify_btree_nr_keys(b);
649 #endif /* _BCACHEFS_BSET_H */