diff options
Diffstat (limited to 'fs/bcachefs/bset.h')
| -rw-r--r-- | fs/bcachefs/bset.h | 541 |
1 files changed, 541 insertions, 0 deletions
diff --git a/fs/bcachefs/bset.h b/fs/bcachefs/bset.h new file mode 100644 index 000000000000..632c2b8c5460 --- /dev/null +++ b/fs/bcachefs/bset.h @@ -0,0 +1,541 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _BCACHEFS_BSET_H +#define _BCACHEFS_BSET_H + +#include <linux/kernel.h> +#include <linux/types.h> + +#include "bcachefs.h" +#include "bkey.h" +#include "bkey_methods.h" +#include "btree_types.h" +#include "util.h" /* for time_stats */ +#include "vstructs.h" + +/* + * BKEYS: + * + * A bkey contains a key, a size field, a variable number of pointers, and some + * ancillary flag bits. + * + * We use two different functions for validating bkeys, bkey_invalid and + * bkey_deleted(). + * + * The one exception to the rule that ptr_invalid() filters out invalid keys is + * that it also filters out keys of size 0 - these are keys that have been + * completely overwritten. It'd be safe to delete these in memory while leaving + * them on disk, just unnecessary work - so we filter them out when resorting + * instead. + * + * We can't filter out stale keys when we're resorting, because garbage + * collection needs to find them to ensure bucket gens don't wrap around - + * unless we're rewriting the btree node those stale keys still exist on disk. + * + * We also implement functions here for removing some number of sectors from the + * front or the back of a bkey - this is mainly used for fixing overlapping + * extents, by removing the overlapping sectors from the older key. + * + * BSETS: + * + * A bset is an array of bkeys laid out contiguously in memory in sorted order, + * along with a header. A btree node is made up of a number of these, written at + * different times. + * + * There could be many of them on disk, but we never allow there to be more than + * 4 in memory - we lazily resort as needed. + * + * We implement code here for creating and maintaining auxiliary search trees + * (described below) for searching an individial bset, and on top of that we + * implement a btree iterator. + * + * BTREE ITERATOR: + * + * Most of the code in bcache doesn't care about an individual bset - it needs + * to search entire btree nodes and iterate over them in sorted order. + * + * The btree iterator code serves both functions; it iterates through the keys + * in a btree node in sorted order, starting from either keys after a specific + * point (if you pass it a search key) or the start of the btree node. + * + * AUXILIARY SEARCH TREES: + * + * Since keys are variable length, we can't use a binary search on a bset - we + * wouldn't be able to find the start of the next key. But binary searches are + * slow anyways, due to terrible cache behaviour; bcache originally used binary + * searches and that code topped out at under 50k lookups/second. + * + * So we need to construct some sort of lookup table. Since we only insert keys + * into the last (unwritten) set, most of the keys within a given btree node are + * usually in sets that are mostly constant. We use two different types of + * lookup tables to take advantage of this. + * + * Both lookup tables share in common that they don't index every key in the + * set; they index one key every BSET_CACHELINE bytes, and then a linear search + * is used for the rest. + * + * For sets that have been written to disk and are no longer being inserted + * into, we construct a binary search tree in an array - traversing a binary + * search tree in an array gives excellent locality of reference and is very + * fast, since both children of any node are adjacent to each other in memory + * (and their grandchildren, and great grandchildren...) - this means + * prefetching can be used to great effect. + * + * It's quite useful performance wise to keep these nodes small - not just + * because they're more likely to be in L2, but also because we can prefetch + * more nodes on a single cacheline and thus prefetch more iterations in advance + * when traversing this tree. + * + * Nodes in the auxiliary search tree must contain both a key to compare against + * (we don't want to fetch the key from the set, that would defeat the purpose), + * and a pointer to the key. We use a few tricks to compress both of these. + * + * To compress the pointer, we take advantage of the fact that one node in the + * search tree corresponds to precisely BSET_CACHELINE bytes in the set. We have + * a function (to_inorder()) that takes the index of a node in a binary tree and + * returns what its index would be in an inorder traversal, so we only have to + * store the low bits of the offset. + * + * The key is 84 bits (KEY_DEV + key->key, the offset on the device). To + * compress that, we take advantage of the fact that when we're traversing the + * search tree at every iteration we know that both our search key and the key + * we're looking for lie within some range - bounded by our previous + * comparisons. (We special case the start of a search so that this is true even + * at the root of the tree). + * + * So we know the key we're looking for is between a and b, and a and b don't + * differ higher than bit 50, we don't need to check anything higher than bit + * 50. + * + * We don't usually need the rest of the bits, either; we only need enough bits + * to partition the key range we're currently checking. Consider key n - the + * key our auxiliary search tree node corresponds to, and key p, the key + * immediately preceding n. The lowest bit we need to store in the auxiliary + * search tree is the highest bit that differs between n and p. + * + * Note that this could be bit 0 - we might sometimes need all 80 bits to do the + * comparison. But we'd really like our nodes in the auxiliary search tree to be + * of fixed size. + * + * The solution is to make them fixed size, and when we're constructing a node + * check if p and n differed in the bits we needed them to. If they don't we + * flag that node, and when doing lookups we fallback to comparing against the + * real key. As long as this doesn't happen to often (and it seems to reliably + * happen a bit less than 1% of the time), we win - even on failures, that key + * is then more likely to be in cache than if we were doing binary searches all + * the way, since we're touching so much less memory. + * + * The keys in the auxiliary search tree are stored in (software) floating + * point, with an exponent and a mantissa. The exponent needs to be big enough + * to address all the bits in the original key, but the number of bits in the + * mantissa is somewhat arbitrary; more bits just gets us fewer failures. + * + * We need 7 bits for the exponent and 3 bits for the key's offset (since keys + * are 8 byte aligned); using 22 bits for the mantissa means a node is 4 bytes. + * We need one node per 128 bytes in the btree node, which means the auxiliary + * search trees take up 3% as much memory as the btree itself. + * + * Constructing these auxiliary search trees is moderately expensive, and we + * don't want to be constantly rebuilding the search tree for the last set + * whenever we insert another key into it. For the unwritten set, we use a much + * simpler lookup table - it's just a flat array, so index i in the lookup table + * corresponds to the i range of BSET_CACHELINE bytes in the set. Indexing + * within each byte range works the same as with the auxiliary search trees. + * + * These are much easier to keep up to date when we insert a key - we do it + * somewhat lazily; when we shift a key up we usually just increment the pointer + * to it, only when it would overflow do we go to the trouble of finding the + * first key in that range of bytes again. + */ + +enum bset_aux_tree_type { + BSET_NO_AUX_TREE, + BSET_RO_AUX_TREE, + BSET_RW_AUX_TREE, +}; + +#define BSET_TREE_NR_TYPES 3 + +#define BSET_NO_AUX_TREE_VAL (U16_MAX) +#define BSET_RW_AUX_TREE_VAL (U16_MAX - 1) + +static inline enum bset_aux_tree_type bset_aux_tree_type(const struct bset_tree *t) +{ + switch (t->extra) { + case BSET_NO_AUX_TREE_VAL: + EBUG_ON(t->size); + return BSET_NO_AUX_TREE; + case BSET_RW_AUX_TREE_VAL: + EBUG_ON(!t->size); + return BSET_RW_AUX_TREE; + default: + EBUG_ON(!t->size); + return BSET_RO_AUX_TREE; + } +} + +/* + * BSET_CACHELINE was originally intended to match the hardware cacheline size - + * it used to be 64, but I realized the lookup code would touch slightly less + * memory if it was 128. + * + * It definites the number of bytes (in struct bset) per struct bkey_float in + * the auxiliar search tree - when we're done searching the bset_float tree we + * have this many bytes left that we do a linear search over. + * + * Since (after level 5) every level of the bset_tree is on a new cacheline, + * we're touching one fewer cacheline in the bset tree in exchange for one more + * cacheline in the linear search - but the linear search might stop before it + * gets to the second cacheline. + */ + +#define BSET_CACHELINE 256 + +static inline size_t btree_keys_cachelines(const struct btree *b) +{ + return (1U << b->byte_order) / BSET_CACHELINE; +} + +static inline size_t btree_aux_data_bytes(const struct btree *b) +{ + return btree_keys_cachelines(b) * 8; +} + +static inline size_t btree_aux_data_u64s(const struct btree *b) +{ + return btree_aux_data_bytes(b) / sizeof(u64); +} + +#define for_each_bset(_b, _t) \ + for (_t = (_b)->set; _t < (_b)->set + (_b)->nsets; _t++) + +#define bset_tree_for_each_key(_b, _t, _k) \ + for (_k = btree_bkey_first(_b, _t); \ + _k != btree_bkey_last(_b, _t); \ + _k = bkey_p_next(_k)) + +static inline bool bset_has_ro_aux_tree(const struct bset_tree *t) +{ + return bset_aux_tree_type(t) == BSET_RO_AUX_TREE; +} + +static inline bool bset_has_rw_aux_tree(struct bset_tree *t) +{ + return bset_aux_tree_type(t) == BSET_RW_AUX_TREE; +} + +static inline void bch2_bset_set_no_aux_tree(struct btree *b, + struct bset_tree *t) +{ + BUG_ON(t < b->set); + + for (; t < b->set + ARRAY_SIZE(b->set); t++) { + t->size = 0; + t->extra = BSET_NO_AUX_TREE_VAL; + t->aux_data_offset = U16_MAX; + } +} + +static inline void btree_node_set_format(struct btree *b, + struct bkey_format f) +{ + int len; + + b->format = f; + b->nr_key_bits = bkey_format_key_bits(&f); + + len = bch2_compile_bkey_format(&b->format, b->aux_data); + BUG_ON(len < 0 || len > U8_MAX); + + b->unpack_fn_len = len; + + bch2_bset_set_no_aux_tree(b, b->set); +} + +static inline struct bset *bset_next_set(struct btree *b, + unsigned block_bytes) +{ + struct bset *i = btree_bset_last(b); + + EBUG_ON(!is_power_of_2(block_bytes)); + + return ((void *) i) + round_up(vstruct_bytes(i), block_bytes); +} + +void bch2_btree_keys_init(struct btree *); + +void bch2_bset_init_first(struct btree *, struct bset *); +void bch2_bset_init_next(struct bch_fs *, struct btree *, + struct btree_node_entry *); +void bch2_bset_build_aux_tree(struct btree *, struct bset_tree *, bool); + +void bch2_bset_insert(struct btree *, struct btree_node_iter *, + struct bkey_packed *, struct bkey_i *, unsigned); +void bch2_bset_delete(struct btree *, struct bkey_packed *, unsigned); + +/* Bkey utility code */ + +/* packed or unpacked */ +static inline int bkey_cmp_p_or_unp(const struct btree *b, + const struct bkey_packed *l, + const struct bkey_packed *r_packed, + const struct bpos *r) +{ + EBUG_ON(r_packed && !bkey_packed(r_packed)); + + if (unlikely(!bkey_packed(l))) + return bpos_cmp(packed_to_bkey_c(l)->p, *r); + + if (likely(r_packed)) + return __bch2_bkey_cmp_packed_format_checked(l, r_packed, b); + + return __bch2_bkey_cmp_left_packed_format_checked(b, l, r); +} + +static inline struct bset_tree * +bch2_bkey_to_bset_inlined(struct btree *b, struct bkey_packed *k) +{ + unsigned offset = __btree_node_key_to_offset(b, k); + struct bset_tree *t; + + for_each_bset(b, t) + if (offset <= t->end_offset) { + EBUG_ON(offset < btree_bkey_first_offset(t)); + return t; + } + + BUG(); +} + +struct bset_tree *bch2_bkey_to_bset(struct btree *, struct bkey_packed *); + +struct bkey_packed *bch2_bkey_prev_filter(struct btree *, struct bset_tree *, + struct bkey_packed *, unsigned); + +static inline struct bkey_packed * +bch2_bkey_prev_all(struct btree *b, struct bset_tree *t, struct bkey_packed *k) +{ + return bch2_bkey_prev_filter(b, t, k, 0); +} + +static inline struct bkey_packed * +bch2_bkey_prev(struct btree *b, struct bset_tree *t, struct bkey_packed *k) +{ + return bch2_bkey_prev_filter(b, t, k, 1); +} + +/* Btree key iteration */ + +void bch2_btree_node_iter_push(struct btree_node_iter *, struct btree *, + const struct bkey_packed *, + const struct bkey_packed *); +void bch2_btree_node_iter_init(struct btree_node_iter *, struct btree *, + struct bpos *); +void bch2_btree_node_iter_init_from_start(struct btree_node_iter *, + struct btree *); +struct bkey_packed *bch2_btree_node_iter_bset_pos(struct btree_node_iter *, + struct btree *, + struct bset_tree *); + +void bch2_btree_node_iter_sort(struct btree_node_iter *, struct btree *); +void bch2_btree_node_iter_set_drop(struct btree_node_iter *, + struct btree_node_iter_set *); +void bch2_btree_node_iter_advance(struct btree_node_iter *, struct btree *); + +#define btree_node_iter_for_each(_iter, _set) \ + for (_set = (_iter)->data; \ + _set < (_iter)->data + ARRAY_SIZE((_iter)->data) && \ + (_set)->k != (_set)->end; \ + _set++) + +static inline bool __btree_node_iter_set_end(struct btree_node_iter *iter, + unsigned i) +{ + return iter->data[i].k == iter->data[i].end; +} + +static inline bool bch2_btree_node_iter_end(struct btree_node_iter *iter) +{ + return __btree_node_iter_set_end(iter, 0); +} + +/* + * When keys compare equal, deleted keys compare first: + * + * XXX: only need to compare pointers for keys that are both within a + * btree_node_iterator - we need to break ties for prev() to work correctly + */ +static inline int bkey_iter_cmp(const struct btree *b, + const struct bkey_packed *l, + const struct bkey_packed *r) +{ + return bch2_bkey_cmp_packed(b, l, r) + ?: (int) bkey_deleted(r) - (int) bkey_deleted(l) + ?: cmp_int(l, r); +} + +static inline int btree_node_iter_cmp(const struct btree *b, + struct btree_node_iter_set l, + struct btree_node_iter_set r) +{ + return bkey_iter_cmp(b, + __btree_node_offset_to_key(b, l.k), + __btree_node_offset_to_key(b, r.k)); +} + +/* These assume r (the search key) is not a deleted key: */ +static inline int bkey_iter_pos_cmp(const struct btree *b, + const struct bkey_packed *l, + const struct bpos *r) +{ + return bkey_cmp_left_packed(b, l, r) + ?: -((int) bkey_deleted(l)); +} + +static inline int bkey_iter_cmp_p_or_unp(const struct btree *b, + const struct bkey_packed *l, + const struct bkey_packed *r_packed, + const struct bpos *r) +{ + return bkey_cmp_p_or_unp(b, l, r_packed, r) + ?: -((int) bkey_deleted(l)); +} + +static inline struct bkey_packed * +__bch2_btree_node_iter_peek_all(struct btree_node_iter *iter, + struct btree *b) +{ + return __btree_node_offset_to_key(b, iter->data->k); +} + +static inline struct bkey_packed * +bch2_btree_node_iter_peek_all(struct btree_node_iter *iter, struct btree *b) +{ + return !bch2_btree_node_iter_end(iter) + ? __btree_node_offset_to_key(b, iter->data->k) + : NULL; +} + +static inline struct bkey_packed * +bch2_btree_node_iter_peek(struct btree_node_iter *iter, struct btree *b) +{ + struct bkey_packed *k; + + while ((k = bch2_btree_node_iter_peek_all(iter, b)) && + bkey_deleted(k)) + bch2_btree_node_iter_advance(iter, b); + + return k; +} + +static inline struct bkey_packed * +bch2_btree_node_iter_next_all(struct btree_node_iter *iter, struct btree *b) +{ + struct bkey_packed *ret = bch2_btree_node_iter_peek_all(iter, b); + + if (ret) + bch2_btree_node_iter_advance(iter, b); + + return ret; +} + +struct bkey_packed *bch2_btree_node_iter_prev_all(struct btree_node_iter *, + struct btree *); +struct bkey_packed *bch2_btree_node_iter_prev(struct btree_node_iter *, + struct btree *); + +struct bkey_s_c bch2_btree_node_iter_peek_unpack(struct btree_node_iter *, + struct btree *, + struct bkey *); + +#define for_each_btree_node_key(b, k, iter) \ + for (bch2_btree_node_iter_init_from_start((iter), (b)); \ + (k = bch2_btree_node_iter_peek((iter), (b))); \ + bch2_btree_node_iter_advance(iter, b)) + +#define for_each_btree_node_key_unpack(b, k, iter, unpacked) \ + for (bch2_btree_node_iter_init_from_start((iter), (b)); \ + (k = bch2_btree_node_iter_peek_unpack((iter), (b), (unpacked))).k;\ + bch2_btree_node_iter_advance(iter, b)) + +/* Accounting: */ + +static inline void btree_keys_account_key(struct btree_nr_keys *n, + unsigned bset, + struct bkey_packed *k, + int sign) +{ + n->live_u64s += k->u64s * sign; + n->bset_u64s[bset] += k->u64s * sign; + + if (bkey_packed(k)) + n->packed_keys += sign; + else + n->unpacked_keys += sign; +} + +static inline void btree_keys_account_val_delta(struct btree *b, + struct bkey_packed *k, + int delta) +{ + struct bset_tree *t = bch2_bkey_to_bset(b, k); + + b->nr.live_u64s += delta; + b->nr.bset_u64s[t - b->set] += delta; +} + +#define btree_keys_account_key_add(_nr, _bset_idx, _k) \ + btree_keys_account_key(_nr, _bset_idx, _k, 1) +#define btree_keys_account_key_drop(_nr, _bset_idx, _k) \ + btree_keys_account_key(_nr, _bset_idx, _k, -1) + +#define btree_account_key_add(_b, _k) \ + btree_keys_account_key(&(_b)->nr, \ + bch2_bkey_to_bset(_b, _k) - (_b)->set, _k, 1) +#define btree_account_key_drop(_b, _k) \ + btree_keys_account_key(&(_b)->nr, \ + bch2_bkey_to_bset(_b, _k) - (_b)->set, _k, -1) + +struct bset_stats { + struct { + size_t nr, bytes; + } sets[BSET_TREE_NR_TYPES]; + + size_t floats; + size_t failed; +}; + +void bch2_btree_keys_stats(const struct btree *, struct bset_stats *); +void bch2_bfloat_to_text(struct printbuf *, struct btree *, + struct bkey_packed *); + +/* Debug stuff */ + +void bch2_dump_bset(struct bch_fs *, struct btree *, struct bset *, unsigned); +void bch2_dump_btree_node(struct bch_fs *, struct btree *); +void bch2_dump_btree_node_iter(struct btree *, struct btree_node_iter *); + +#ifdef CONFIG_BCACHEFS_DEBUG + +void __bch2_verify_btree_nr_keys(struct btree *); +void bch2_btree_node_iter_verify(struct btree_node_iter *, struct btree *); +void bch2_verify_insert_pos(struct btree *, struct bkey_packed *, + struct bkey_packed *, unsigned); + +#else + +static inline void __bch2_verify_btree_nr_keys(struct btree *b) {} +static inline void bch2_btree_node_iter_verify(struct btree_node_iter *iter, + struct btree *b) {} +static inline void bch2_verify_insert_pos(struct btree *b, + struct bkey_packed *where, + struct bkey_packed *insert, + unsigned clobber_u64s) {} +#endif + +static inline void bch2_verify_btree_nr_keys(struct btree *b) +{ + if (bch2_debug_check_btree_accounting) + __bch2_verify_btree_nr_keys(b); +} + +#endif /* _BCACHEFS_BSET_H */ |