1 // SPDX-License-Identifier: GPL-2.0
4 #include "btree_cache.h"
6 #include "btree_iter.h"
7 #include "btree_locking.h"
10 #include <linux/prefetch.h>
11 #include <linux/sched/mm.h>
12 #include <trace/events/bcachefs.h>
14 const char * const bch2_btree_ids[] = {
15 #define x(kwd, val, name) name,
21 void bch2_recalc_btree_reserve(struct bch_fs *c)
23 unsigned i, reserve = 16;
25 if (!c->btree_roots[0].b)
28 for (i = 0; i < BTREE_ID_NR; i++)
29 if (c->btree_roots[i].b)
30 reserve += min_t(unsigned, 1,
31 c->btree_roots[i].b->level) * 8;
33 c->btree_cache.reserve = reserve;
36 static inline unsigned btree_cache_can_free(struct btree_cache *bc)
38 return max_t(int, 0, bc->used - bc->reserve);
41 static void __btree_node_data_free(struct bch_fs *c, struct btree *b)
43 EBUG_ON(btree_node_write_in_flight(b));
45 kvpfree(b->data, btree_bytes(c));
47 bch2_btree_keys_free(b);
50 static void btree_node_data_free(struct bch_fs *c, struct btree *b)
52 struct btree_cache *bc = &c->btree_cache;
54 __btree_node_data_free(c, b);
56 list_move(&b->list, &bc->freed);
59 static int bch2_btree_cache_cmp_fn(struct rhashtable_compare_arg *arg,
62 const struct btree *b = obj;
63 const u64 *v = arg->key;
65 return PTR_HASH(&b->key) == *v ? 0 : 1;
68 static const struct rhashtable_params bch_btree_cache_params = {
69 .head_offset = offsetof(struct btree, hash),
70 .key_offset = offsetof(struct btree, key.v),
71 .key_len = sizeof(struct bch_extent_ptr),
72 .obj_cmpfn = bch2_btree_cache_cmp_fn,
75 static void btree_node_data_alloc(struct bch_fs *c, struct btree *b, gfp_t gfp)
77 struct btree_cache *bc = &c->btree_cache;
79 b->data = kvpmalloc(btree_bytes(c), gfp);
83 if (bch2_btree_keys_alloc(b, btree_page_order(c), gfp))
86 memset(&b->data->csum, 0, sizeof b->data->csum);
90 list_move(&b->list, &bc->freeable);
93 kvpfree(b->data, btree_bytes(c));
95 list_move(&b->list, &bc->freed);
98 static struct btree *btree_node_mem_alloc(struct bch_fs *c, gfp_t gfp)
100 struct btree *b = kzalloc(sizeof(struct btree), gfp);
104 bkey_btree_ptr_init(&b->key);
105 six_lock_init(&b->lock);
106 INIT_LIST_HEAD(&b->list);
107 INIT_LIST_HEAD(&b->write_blocked);
109 btree_node_data_alloc(c, b, gfp);
110 return b->data ? b : NULL;
113 /* Btree in memory cache - hash table */
115 void bch2_btree_node_hash_remove(struct btree_cache *bc, struct btree *b)
117 rhashtable_remove_fast(&bc->table, &b->hash, bch_btree_cache_params);
119 /* Cause future lookups for this node to fail: */
120 PTR_HASH(&b->key) = 0;
123 int __bch2_btree_node_hash_insert(struct btree_cache *bc, struct btree *b)
125 return rhashtable_lookup_insert_fast(&bc->table, &b->hash,
126 bch_btree_cache_params);
129 int bch2_btree_node_hash_insert(struct btree_cache *bc, struct btree *b,
130 unsigned level, enum btree_id id)
137 mutex_lock(&bc->lock);
138 ret = __bch2_btree_node_hash_insert(bc, b);
140 list_add(&b->list, &bc->live);
141 mutex_unlock(&bc->lock);
147 static inline struct btree *btree_cache_find(struct btree_cache *bc,
148 const struct bkey_i *k)
150 return rhashtable_lookup_fast(&bc->table, &PTR_HASH(k),
151 bch_btree_cache_params);
155 * this version is for btree nodes that have already been freed (we're not
156 * reaping a real btree node)
158 static int __btree_node_reclaim(struct bch_fs *c, struct btree *b, bool flush)
160 struct btree_cache *bc = &c->btree_cache;
163 lockdep_assert_held(&bc->lock);
165 if (!six_trylock_intent(&b->lock))
168 if (!six_trylock_write(&b->lock))
169 goto out_unlock_intent;
171 if (btree_node_noevict(b))
174 if (!btree_node_may_write(b))
177 if (btree_node_dirty(b) &&
178 test_bit(BCH_FS_HOLD_BTREE_WRITES, &c->flags))
181 if (btree_node_dirty(b) ||
182 btree_node_write_in_flight(b) ||
183 btree_node_read_in_flight(b)) {
187 wait_on_bit_io(&b->flags, BTREE_NODE_read_in_flight,
188 TASK_UNINTERRUPTIBLE);
191 * Using the underscore version because we don't want to compact
192 * bsets after the write, since this node is about to be evicted
193 * - unless btree verify mode is enabled, since it runs out of
194 * the post write cleanup:
196 if (verify_btree_ondisk(c))
197 bch2_btree_node_write(c, b, SIX_LOCK_intent);
199 __bch2_btree_node_write(c, b, SIX_LOCK_read);
201 /* wait for any in flight btree write */
202 btree_node_wait_on_io(b);
205 if (PTR_HASH(&b->key) && !ret)
206 trace_btree_node_reap(c, b);
209 six_unlock_write(&b->lock);
211 six_unlock_intent(&b->lock);
216 static int btree_node_reclaim(struct bch_fs *c, struct btree *b)
218 return __btree_node_reclaim(c, b, false);
221 static int btree_node_write_and_reclaim(struct bch_fs *c, struct btree *b)
223 return __btree_node_reclaim(c, b, true);
226 static unsigned long bch2_btree_cache_scan(struct shrinker *shrink,
227 struct shrink_control *sc)
229 struct bch_fs *c = container_of(shrink, struct bch_fs,
231 struct btree_cache *bc = &c->btree_cache;
233 unsigned long nr = sc->nr_to_scan;
234 unsigned long can_free;
235 unsigned long touched = 0;
236 unsigned long freed = 0;
239 if (btree_shrinker_disabled(c))
242 /* Return -1 if we can't do anything right now */
243 if (sc->gfp_mask & __GFP_IO)
244 mutex_lock(&bc->lock);
245 else if (!mutex_trylock(&bc->lock))
249 * It's _really_ critical that we don't free too many btree nodes - we
250 * have to always leave ourselves a reserve. The reserve is how we
251 * guarantee that allocating memory for a new btree node can always
252 * succeed, so that inserting keys into the btree can always succeed and
253 * IO can always make forward progress:
255 nr /= btree_pages(c);
256 can_free = btree_cache_can_free(bc);
257 nr = min_t(unsigned long, nr, can_free);
260 list_for_each_entry_safe(b, t, &bc->freeable, list) {
267 !btree_node_reclaim(c, b)) {
268 btree_node_data_free(c, b);
269 six_unlock_write(&b->lock);
270 six_unlock_intent(&b->lock);
275 list_for_each_entry_safe(b, t, &bc->live, list) {
280 if (&t->list != &bc->live)
281 list_move_tail(&bc->live, &t->list);
285 if (!btree_node_accessed(b) &&
286 !btree_node_reclaim(c, b)) {
287 /* can't call bch2_btree_node_hash_remove under lock */
289 if (&t->list != &bc->live)
290 list_move_tail(&bc->live, &t->list);
292 btree_node_data_free(c, b);
293 mutex_unlock(&bc->lock);
295 bch2_btree_node_hash_remove(bc, b);
296 six_unlock_write(&b->lock);
297 six_unlock_intent(&b->lock);
302 if (sc->gfp_mask & __GFP_IO)
303 mutex_lock(&bc->lock);
304 else if (!mutex_trylock(&bc->lock))
308 clear_btree_node_accessed(b);
311 mutex_unlock(&bc->lock);
313 return (unsigned long) freed * btree_pages(c);
316 static unsigned long bch2_btree_cache_count(struct shrinker *shrink,
317 struct shrink_control *sc)
319 struct bch_fs *c = container_of(shrink, struct bch_fs,
321 struct btree_cache *bc = &c->btree_cache;
323 if (btree_shrinker_disabled(c))
326 return btree_cache_can_free(bc) * btree_pages(c);
329 void bch2_fs_btree_cache_exit(struct bch_fs *c)
331 struct btree_cache *bc = &c->btree_cache;
335 if (bc->shrink.list.next)
336 unregister_shrinker(&bc->shrink);
338 mutex_lock(&bc->lock);
340 #ifdef CONFIG_BCACHEFS_DEBUG
342 list_move(&c->verify_data->list, &bc->live);
344 kvpfree(c->verify_ondisk, btree_bytes(c));
347 for (i = 0; i < BTREE_ID_NR; i++)
348 if (c->btree_roots[i].b)
349 list_add(&c->btree_roots[i].b->list, &bc->live);
351 list_splice(&bc->freeable, &bc->live);
353 while (!list_empty(&bc->live)) {
354 b = list_first_entry(&bc->live, struct btree, list);
356 BUG_ON(btree_node_read_in_flight(b) ||
357 btree_node_write_in_flight(b));
359 if (btree_node_dirty(b))
360 bch2_btree_complete_write(c, b, btree_current_write(b));
361 clear_btree_node_dirty(b);
363 btree_node_data_free(c, b);
366 while (!list_empty(&bc->freed)) {
367 b = list_first_entry(&bc->freed, struct btree, list);
372 mutex_unlock(&bc->lock);
374 if (bc->table_init_done)
375 rhashtable_destroy(&bc->table);
378 int bch2_fs_btree_cache_init(struct bch_fs *c)
380 struct btree_cache *bc = &c->btree_cache;
384 pr_verbose_init(c->opts, "");
386 ret = rhashtable_init(&bc->table, &bch_btree_cache_params);
390 bc->table_init_done = true;
392 bch2_recalc_btree_reserve(c);
394 for (i = 0; i < bc->reserve; i++)
395 if (!btree_node_mem_alloc(c, GFP_KERNEL)) {
400 list_splice_init(&bc->live, &bc->freeable);
402 #ifdef CONFIG_BCACHEFS_DEBUG
403 mutex_init(&c->verify_lock);
405 c->verify_ondisk = kvpmalloc(btree_bytes(c), GFP_KERNEL);
406 if (!c->verify_ondisk) {
411 c->verify_data = btree_node_mem_alloc(c, GFP_KERNEL);
412 if (!c->verify_data) {
417 list_del_init(&c->verify_data->list);
420 bc->shrink.count_objects = bch2_btree_cache_count;
421 bc->shrink.scan_objects = bch2_btree_cache_scan;
422 bc->shrink.seeks = 4;
423 bc->shrink.batch = btree_pages(c) * 2;
424 register_shrinker(&bc->shrink);
426 pr_verbose_init(c->opts, "ret %i", ret);
430 void bch2_fs_btree_cache_init_early(struct btree_cache *bc)
432 mutex_init(&bc->lock);
433 INIT_LIST_HEAD(&bc->live);
434 INIT_LIST_HEAD(&bc->freeable);
435 INIT_LIST_HEAD(&bc->freed);
439 * We can only have one thread cannibalizing other cached btree nodes at a time,
440 * or we'll deadlock. We use an open coded mutex to ensure that, which a
441 * cannibalize_bucket() will take. This means every time we unlock the root of
442 * the btree, we need to release this lock if we have it held.
444 void bch2_btree_cache_cannibalize_unlock(struct bch_fs *c)
446 struct btree_cache *bc = &c->btree_cache;
448 if (bc->alloc_lock == current) {
449 trace_btree_node_cannibalize_unlock(c);
450 bc->alloc_lock = NULL;
451 closure_wake_up(&bc->alloc_wait);
455 int bch2_btree_cache_cannibalize_lock(struct bch_fs *c, struct closure *cl)
457 struct btree_cache *bc = &c->btree_cache;
458 struct task_struct *old;
460 old = cmpxchg(&bc->alloc_lock, NULL, current);
461 if (old == NULL || old == current)
465 trace_btree_node_cannibalize_lock_fail(c);
469 closure_wait(&bc->alloc_wait, cl);
471 /* Try again, after adding ourselves to waitlist */
472 old = cmpxchg(&bc->alloc_lock, NULL, current);
473 if (old == NULL || old == current) {
475 closure_wake_up(&bc->alloc_wait);
479 trace_btree_node_cannibalize_lock_fail(c);
483 trace_btree_node_cannibalize_lock(c);
487 static struct btree *btree_node_cannibalize(struct bch_fs *c)
489 struct btree_cache *bc = &c->btree_cache;
492 list_for_each_entry_reverse(b, &bc->live, list)
493 if (!btree_node_reclaim(c, b))
497 list_for_each_entry_reverse(b, &bc->live, list)
498 if (!btree_node_write_and_reclaim(c, b))
502 * Rare case: all nodes were intent-locked.
505 WARN_ONCE(1, "btree cache cannibalize failed\n");
510 struct btree *bch2_btree_node_mem_alloc(struct bch_fs *c)
512 struct btree_cache *bc = &c->btree_cache;
514 u64 start_time = local_clock();
517 flags = memalloc_nofs_save();
518 mutex_lock(&bc->lock);
521 * btree_free() doesn't free memory; it sticks the node on the end of
522 * the list. Check if there's any freed nodes there:
524 list_for_each_entry(b, &bc->freeable, list)
525 if (!btree_node_reclaim(c, b))
529 * We never free struct btree itself, just the memory that holds the on
530 * disk node. Check the freed list before allocating a new one:
532 list_for_each_entry(b, &bc->freed, list)
533 if (!btree_node_reclaim(c, b)) {
534 btree_node_data_alloc(c, b, __GFP_NOWARN|GFP_NOIO);
538 six_unlock_write(&b->lock);
539 six_unlock_intent(&b->lock);
543 b = btree_node_mem_alloc(c, __GFP_NOWARN|GFP_NOIO);
547 BUG_ON(!six_trylock_intent(&b->lock));
548 BUG_ON(!six_trylock_write(&b->lock));
550 BUG_ON(btree_node_hashed(b));
551 BUG_ON(btree_node_write_in_flight(b));
553 list_del_init(&b->list);
554 mutex_unlock(&bc->lock);
555 memalloc_nofs_restore(flags);
562 b->whiteout_u64s = 0;
563 b->uncompacted_whiteout_u64s = 0;
564 bch2_btree_keys_init(b, &c->expensive_debug_checks);
566 bch2_time_stats_update(&c->times[BCH_TIME_btree_node_mem_alloc],
571 /* Try to cannibalize another cached btree node: */
572 if (bc->alloc_lock == current) {
573 b = btree_node_cannibalize(c);
574 list_del_init(&b->list);
575 mutex_unlock(&bc->lock);
577 bch2_btree_node_hash_remove(bc, b);
579 trace_btree_node_cannibalize(c);
583 mutex_unlock(&bc->lock);
584 return ERR_PTR(-ENOMEM);
587 /* Slowpath, don't want it inlined into btree_iter_traverse() */
588 static noinline struct btree *bch2_btree_node_fill(struct bch_fs *c,
589 struct btree_iter *iter,
590 const struct bkey_i *k,
592 enum six_lock_type lock_type,
595 struct btree_cache *bc = &c->btree_cache;
599 * Parent node must be locked, else we could read in a btree node that's
602 BUG_ON(!btree_node_locked(iter, level + 1));
603 BUG_ON(level >= BTREE_MAX_DEPTH);
605 b = bch2_btree_node_mem_alloc(c);
609 bkey_copy(&b->key, k);
610 if (bch2_btree_node_hash_insert(bc, b, level, iter->btree_id)) {
611 /* raced with another fill: */
613 /* mark as unhashed... */
614 PTR_HASH(&b->key) = 0;
616 mutex_lock(&bc->lock);
617 list_add(&b->list, &bc->freeable);
618 mutex_unlock(&bc->lock);
620 six_unlock_write(&b->lock);
621 six_unlock_intent(&b->lock);
626 * If the btree node wasn't cached, we can't drop our lock on
627 * the parent until after it's added to the cache - because
628 * otherwise we could race with a btree_split() freeing the node
629 * we're trying to lock.
631 * But the deadlock described below doesn't exist in this case,
632 * so it's safe to not drop the parent lock until here:
634 if (btree_node_read_locked(iter, level + 1))
635 btree_node_unlock(iter, level + 1);
637 bch2_btree_node_read(c, b, sync);
639 six_unlock_write(&b->lock);
642 six_unlock_intent(&b->lock);
646 if (lock_type == SIX_LOCK_read)
647 six_lock_downgrade(&b->lock);
653 * bch_btree_node_get - find a btree node in the cache and lock it, reading it
654 * in from disk if necessary.
656 * If IO is necessary and running under generic_make_request, returns -EAGAIN.
658 * The btree node will have either a read or a write lock held, depending on
659 * the @write parameter.
661 struct btree *bch2_btree_node_get(struct bch_fs *c, struct btree_iter *iter,
662 const struct bkey_i *k, unsigned level,
663 enum six_lock_type lock_type)
665 struct btree_cache *bc = &c->btree_cache;
670 * XXX: locking optimization
672 * we can make the locking looser here - caller can drop lock on parent
673 * node before locking child node (and potentially blocking): we just
674 * have to have bch2_btree_node_fill() call relock on the parent and
675 * return -EINTR if that fails
677 EBUG_ON(!btree_node_locked(iter, level + 1));
678 EBUG_ON(level >= BTREE_MAX_DEPTH);
680 b = btree_cache_find(bc, k);
683 * We must have the parent locked to call bch2_btree_node_fill(),
684 * else we could read in a btree node from disk that's been
687 b = bch2_btree_node_fill(c, iter, k, level, lock_type, true);
689 /* We raced and found the btree node in the cache */
697 * There's a potential deadlock with splits and insertions into
698 * interior nodes we have to avoid:
700 * The other thread might be holding an intent lock on the node
701 * we want, and they want to update its parent node so they're
702 * going to upgrade their intent lock on the parent node to a
705 * But if we're holding a read lock on the parent, and we're
706 * trying to get the intent lock they're holding, we deadlock.
708 * So to avoid this we drop the read locks on parent nodes when
709 * we're starting to take intent locks - and handle the race.
711 * The race is that they might be about to free the node we
712 * want, and dropping our read lock on the parent node lets them
713 * update the parent marking the node we want as freed, and then
716 * To guard against this, btree nodes are evicted from the cache
717 * when they're freed - and PTR_HASH() is zeroed out, which we
718 * check for after we lock the node.
720 * Then, bch2_btree_node_relock() on the parent will fail - because
721 * the parent was modified, when the pointer to the node we want
722 * was removed - and we'll bail out:
724 if (btree_node_read_locked(iter, level + 1))
725 btree_node_unlock(iter, level + 1);
727 if (!btree_node_lock(b, k->k.p, level, iter, lock_type))
728 return ERR_PTR(-EINTR);
730 if (unlikely(PTR_HASH(&b->key) != PTR_HASH(k) ||
733 six_unlock_type(&b->lock, lock_type);
734 if (bch2_btree_node_relock(iter, level + 1))
737 trace_trans_restart_btree_node_reused(iter->trans->ip);
738 return ERR_PTR(-EINTR);
742 wait_on_bit_io(&b->flags, BTREE_NODE_read_in_flight,
743 TASK_UNINTERRUPTIBLE);
745 prefetch(b->aux_data);
747 for_each_bset(b, t) {
748 void *p = (u64 *) b->aux_data + t->aux_data_offset;
750 prefetch(p + L1_CACHE_BYTES * 0);
751 prefetch(p + L1_CACHE_BYTES * 1);
752 prefetch(p + L1_CACHE_BYTES * 2);
755 /* avoid atomic set bit if it's not needed: */
756 if (btree_node_accessed(b))
757 set_btree_node_accessed(b);
759 if (unlikely(btree_node_read_error(b))) {
760 six_unlock_type(&b->lock, lock_type);
761 return ERR_PTR(-EIO);
764 EBUG_ON(b->btree_id != iter->btree_id ||
765 BTREE_NODE_LEVEL(b->data) != level ||
766 bkey_cmp(b->data->max_key, k->k.p));
771 struct btree *bch2_btree_node_get_sibling(struct bch_fs *c,
772 struct btree_iter *iter,
774 enum btree_node_sibling sib)
776 struct btree_trans *trans = iter->trans;
777 struct btree *parent;
778 struct btree_node_iter node_iter;
779 struct bkey_packed *k;
781 struct btree *ret = NULL;
782 unsigned level = b->level;
784 parent = btree_iter_node(iter, level + 1);
788 if (!bch2_btree_node_relock(iter, level + 1)) {
789 ret = ERR_PTR(-EINTR);
793 node_iter = iter->l[parent->level].iter;
795 k = bch2_btree_node_iter_peek_all(&node_iter, parent);
796 BUG_ON(bkey_cmp_left_packed(parent, k, &b->key.k.p));
798 k = sib == btree_prev_sib
799 ? bch2_btree_node_iter_prev(&node_iter, parent)
800 : (bch2_btree_node_iter_advance(&node_iter, parent),
801 bch2_btree_node_iter_peek(&node_iter, parent));
805 bch2_bkey_unpack(parent, &tmp.k, k);
807 ret = bch2_btree_node_get(c, iter, &tmp.k, level,
810 if (PTR_ERR_OR_ZERO(ret) == -EINTR && !trans->nounlock) {
811 struct btree_iter *linked;
813 if (!bch2_btree_node_relock(iter, level + 1))
817 * We might have got -EINTR because trylock failed, and we're
818 * holding other locks that would cause us to deadlock:
820 trans_for_each_iter(trans, linked)
821 if (btree_iter_cmp(iter, linked) < 0)
822 __bch2_btree_iter_unlock(linked);
824 if (sib == btree_prev_sib)
825 btree_node_unlock(iter, level);
827 ret = bch2_btree_node_get(c, iter, &tmp.k, level,
831 * before btree_iter_relock() calls btree_iter_verify_locks():
833 if (btree_lock_want(iter, level + 1) == BTREE_NODE_UNLOCKED)
834 btree_node_unlock(iter, level + 1);
836 if (!bch2_btree_node_relock(iter, level)) {
837 btree_iter_set_dirty(iter, BTREE_ITER_NEED_RELOCK);
840 six_unlock_intent(&ret->lock);
841 ret = ERR_PTR(-EINTR);
845 bch2_trans_relock(trans);
848 if (btree_lock_want(iter, level + 1) == BTREE_NODE_UNLOCKED)
849 btree_node_unlock(iter, level + 1);
851 if (PTR_ERR_OR_ZERO(ret) == -EINTR)
852 bch2_btree_iter_upgrade(iter, level + 2);
854 BUG_ON(!IS_ERR(ret) && !btree_node_locked(iter, level));
856 if (!IS_ERR_OR_NULL(ret)) {
857 struct btree *n1 = ret, *n2 = b;
859 if (sib != btree_prev_sib)
862 BUG_ON(bkey_cmp(btree_type_successor(n1->btree_id,
867 bch2_btree_trans_verify_locks(trans);
872 void bch2_btree_node_prefetch(struct bch_fs *c, struct btree_iter *iter,
873 const struct bkey_i *k, unsigned level)
875 struct btree_cache *bc = &c->btree_cache;
878 BUG_ON(!btree_node_locked(iter, level + 1));
879 BUG_ON(level >= BTREE_MAX_DEPTH);
881 b = btree_cache_find(bc, k);
885 bch2_btree_node_fill(c, iter, k, level, SIX_LOCK_read, false);
888 void bch2_btree_node_to_text(struct printbuf *out, struct bch_fs *c,
891 const struct bkey_format *f = &b->format;
892 struct bset_stats stats;
894 memset(&stats, 0, sizeof(stats));
896 bch2_btree_keys_stats(b, &stats);
899 "l %u %llu:%llu - %llu:%llu:\n"
902 b->data->min_key.inode,
903 b->data->min_key.offset,
904 b->data->max_key.inode,
905 b->data->max_key.offset);
906 bch2_val_to_text(out, c, bkey_i_to_s_c(&b->key));
908 " format: u64s %u fields %u %u %u %u %u\n"
909 " unpack fn len: %u\n"
910 " bytes used %zu/%zu (%zu%% full)\n"
911 " sib u64s: %u, %u (merge threshold %zu)\n"
912 " nr packed keys %u\n"
913 " nr unpacked keys %u\n"
915 " failed unpacked %zu\n"
917 " failed overflow %zu\n",
919 f->bits_per_field[0],
920 f->bits_per_field[1],
921 f->bits_per_field[2],
922 f->bits_per_field[3],
923 f->bits_per_field[4],
925 b->nr.live_u64s * sizeof(u64),
926 btree_bytes(c) - sizeof(struct btree_node),
927 b->nr.live_u64s * 100 / btree_max_u64s(c),
930 BTREE_FOREGROUND_MERGE_THRESHOLD(c),
934 stats.failed_unpacked,
936 stats.failed_overflow);