3 #include "btree_cache.h"
5 #include "btree_iter.h"
6 #include "btree_locking.h"
10 #include <linux/prefetch.h>
11 #include <trace/events/bcachefs.h>
13 #define DEF_BTREE_ID(kwd, val, name) name,
15 const char * const bch2_btree_ids[] = {
16 DEFINE_BCH_BTREE_IDS()
22 void bch2_recalc_btree_reserve(struct bch_fs *c)
24 unsigned i, reserve = 16;
26 if (!c->btree_roots[0].b)
29 for (i = 0; i < BTREE_ID_NR; i++)
30 if (c->btree_roots[i].b)
31 reserve += min_t(unsigned, 1,
32 c->btree_roots[i].b->level) * 8;
34 c->btree_cache.reserve = reserve;
37 static inline unsigned btree_cache_can_free(struct btree_cache *bc)
39 return max_t(int, 0, bc->used - bc->reserve);
42 static void __btree_node_data_free(struct bch_fs *c, struct btree *b)
44 EBUG_ON(btree_node_write_in_flight(b));
46 kvpfree(b->data, btree_bytes(c));
48 bch2_btree_keys_free(b);
51 static void btree_node_data_free(struct bch_fs *c, struct btree *b)
53 struct btree_cache *bc = &c->btree_cache;
55 __btree_node_data_free(c, b);
57 list_move(&b->list, &bc->freed);
60 static int bch2_btree_cache_cmp_fn(struct rhashtable_compare_arg *arg,
63 const struct btree *b = obj;
64 const u64 *v = arg->key;
66 return PTR_HASH(&b->key) == *v ? 0 : 1;
69 static const struct rhashtable_params bch_btree_cache_params = {
70 .head_offset = offsetof(struct btree, hash),
71 .key_offset = offsetof(struct btree, key.v),
72 .key_len = sizeof(struct bch_extent_ptr),
73 .obj_cmpfn = bch2_btree_cache_cmp_fn,
76 static void btree_node_data_alloc(struct bch_fs *c, struct btree *b, gfp_t gfp)
78 struct btree_cache *bc = &c->btree_cache;
80 b->data = kvpmalloc(btree_bytes(c), gfp);
84 if (bch2_btree_keys_alloc(b, btree_page_order(c), gfp))
88 list_move(&b->list, &bc->freeable);
91 kvpfree(b->data, btree_bytes(c));
93 list_move(&b->list, &bc->freed);
96 static struct btree *btree_node_mem_alloc(struct bch_fs *c, gfp_t gfp)
98 struct btree *b = kzalloc(sizeof(struct btree), gfp);
102 bkey_extent_init(&b->key);
103 six_lock_init(&b->lock);
104 INIT_LIST_HEAD(&b->list);
105 INIT_LIST_HEAD(&b->write_blocked);
107 btree_node_data_alloc(c, b, gfp);
108 return b->data ? b : NULL;
111 /* Btree in memory cache - hash table */
113 void bch2_btree_node_hash_remove(struct btree_cache *bc, struct btree *b)
115 rhashtable_remove_fast(&bc->table, &b->hash, bch_btree_cache_params);
117 /* Cause future lookups for this node to fail: */
118 bkey_i_to_extent(&b->key)->v._data[0] = 0;
121 int __bch2_btree_node_hash_insert(struct btree_cache *bc, struct btree *b)
123 return rhashtable_lookup_insert_fast(&bc->table, &b->hash,
124 bch_btree_cache_params);
127 int bch2_btree_node_hash_insert(struct btree_cache *bc, struct btree *b,
128 unsigned level, enum btree_id id)
135 mutex_lock(&bc->lock);
136 ret = __bch2_btree_node_hash_insert(bc, b);
138 list_add(&b->list, &bc->live);
139 mutex_unlock(&bc->lock);
145 static inline struct btree *btree_cache_find(struct btree_cache *bc,
146 const struct bkey_i *k)
148 return rhashtable_lookup_fast(&bc->table, &PTR_HASH(k),
149 bch_btree_cache_params);
153 * this version is for btree nodes that have already been freed (we're not
154 * reaping a real btree node)
156 static int __btree_node_reclaim(struct bch_fs *c, struct btree *b, bool flush)
158 struct btree_cache *bc = &c->btree_cache;
161 lockdep_assert_held(&bc->lock);
163 if (!six_trylock_intent(&b->lock))
166 if (!six_trylock_write(&b->lock))
167 goto out_unlock_intent;
169 if (btree_node_noevict(b))
172 if (!btree_node_may_write(b))
175 if (btree_node_dirty(b) ||
176 btree_node_write_in_flight(b) ||
177 btree_node_read_in_flight(b)) {
181 wait_on_bit_io(&b->flags, BTREE_NODE_read_in_flight,
182 TASK_UNINTERRUPTIBLE);
185 * Using the underscore version because we don't want to compact
186 * bsets after the write, since this node is about to be evicted
187 * - unless btree verify mode is enabled, since it runs out of
188 * the post write cleanup:
190 if (verify_btree_ondisk(c))
191 bch2_btree_node_write(c, b, SIX_LOCK_intent);
193 __bch2_btree_node_write(c, b, SIX_LOCK_read);
195 /* wait for any in flight btree write */
196 btree_node_wait_on_io(b);
199 if (PTR_HASH(&b->key) && !ret)
200 trace_btree_node_reap(c, b);
203 six_unlock_write(&b->lock);
205 six_unlock_intent(&b->lock);
210 static int btree_node_reclaim(struct bch_fs *c, struct btree *b)
212 return __btree_node_reclaim(c, b, false);
215 static int btree_node_write_and_reclaim(struct bch_fs *c, struct btree *b)
217 return __btree_node_reclaim(c, b, true);
220 static unsigned long bch2_btree_cache_scan(struct shrinker *shrink,
221 struct shrink_control *sc)
223 struct bch_fs *c = container_of(shrink, struct bch_fs,
225 struct btree_cache *bc = &c->btree_cache;
227 unsigned long nr = sc->nr_to_scan;
228 unsigned long can_free;
229 unsigned long touched = 0;
230 unsigned long freed = 0;
233 if (btree_shrinker_disabled(c))
236 /* Return -1 if we can't do anything right now */
237 if (sc->gfp_mask & __GFP_IO)
238 mutex_lock(&bc->lock);
239 else if (!mutex_trylock(&bc->lock))
243 * It's _really_ critical that we don't free too many btree nodes - we
244 * have to always leave ourselves a reserve. The reserve is how we
245 * guarantee that allocating memory for a new btree node can always
246 * succeed, so that inserting keys into the btree can always succeed and
247 * IO can always make forward progress:
249 nr /= btree_pages(c);
250 can_free = btree_cache_can_free(bc);
251 nr = min_t(unsigned long, nr, can_free);
254 list_for_each_entry_safe(b, t, &bc->freeable, list) {
261 !btree_node_reclaim(c, b)) {
262 btree_node_data_free(c, b);
263 six_unlock_write(&b->lock);
264 six_unlock_intent(&b->lock);
269 list_for_each_entry_safe(b, t, &bc->live, list) {
274 if (&t->list != &bc->live)
275 list_move_tail(&bc->live, &t->list);
279 if (!btree_node_accessed(b) &&
280 !btree_node_reclaim(c, b)) {
281 /* can't call bch2_btree_node_hash_remove under lock */
283 if (&t->list != &bc->live)
284 list_move_tail(&bc->live, &t->list);
286 btree_node_data_free(c, b);
287 mutex_unlock(&bc->lock);
289 bch2_btree_node_hash_remove(bc, b);
290 six_unlock_write(&b->lock);
291 six_unlock_intent(&b->lock);
296 if (sc->gfp_mask & __GFP_IO)
297 mutex_lock(&bc->lock);
298 else if (!mutex_trylock(&bc->lock))
302 clear_btree_node_accessed(b);
305 mutex_unlock(&bc->lock);
307 return (unsigned long) freed * btree_pages(c);
310 static unsigned long bch2_btree_cache_count(struct shrinker *shrink,
311 struct shrink_control *sc)
313 struct bch_fs *c = container_of(shrink, struct bch_fs,
315 struct btree_cache *bc = &c->btree_cache;
317 if (btree_shrinker_disabled(c))
320 return btree_cache_can_free(bc) * btree_pages(c);
323 void bch2_fs_btree_cache_exit(struct bch_fs *c)
325 struct btree_cache *bc = &c->btree_cache;
329 if (bc->shrink.list.next)
330 unregister_shrinker(&bc->shrink);
332 mutex_lock(&bc->lock);
334 #ifdef CONFIG_BCACHEFS_DEBUG
336 list_move(&c->verify_data->list, &bc->live);
338 kvpfree(c->verify_ondisk, btree_bytes(c));
341 for (i = 0; i < BTREE_ID_NR; i++)
342 if (c->btree_roots[i].b)
343 list_add(&c->btree_roots[i].b->list, &bc->live);
345 list_splice(&bc->freeable, &bc->live);
347 while (!list_empty(&bc->live)) {
348 b = list_first_entry(&bc->live, struct btree, list);
350 BUG_ON(btree_node_read_in_flight(b) ||
351 btree_node_write_in_flight(b));
353 if (btree_node_dirty(b))
354 bch2_btree_complete_write(c, b, btree_current_write(b));
355 clear_btree_node_dirty(b);
357 btree_node_data_free(c, b);
360 while (!list_empty(&bc->freed)) {
361 b = list_first_entry(&bc->freed, struct btree, list);
366 mutex_unlock(&bc->lock);
368 if (bc->table_init_done)
369 rhashtable_destroy(&bc->table);
372 int bch2_fs_btree_cache_init(struct bch_fs *c)
374 struct btree_cache *bc = &c->btree_cache;
378 pr_verbose_init(c->opts, "");
380 ret = rhashtable_init(&bc->table, &bch_btree_cache_params);
384 bc->table_init_done = true;
386 bch2_recalc_btree_reserve(c);
388 for (i = 0; i < bc->reserve; i++)
389 if (!btree_node_mem_alloc(c, GFP_KERNEL)) {
394 list_splice_init(&bc->live, &bc->freeable);
396 #ifdef CONFIG_BCACHEFS_DEBUG
397 mutex_init(&c->verify_lock);
399 c->verify_ondisk = kvpmalloc(btree_bytes(c), GFP_KERNEL);
400 if (!c->verify_ondisk) {
405 c->verify_data = btree_node_mem_alloc(c, GFP_KERNEL);
406 if (!c->verify_data) {
411 list_del_init(&c->verify_data->list);
414 bc->shrink.count_objects = bch2_btree_cache_count;
415 bc->shrink.scan_objects = bch2_btree_cache_scan;
416 bc->shrink.seeks = 4;
417 bc->shrink.batch = btree_pages(c) * 2;
418 register_shrinker(&bc->shrink);
420 pr_verbose_init(c->opts, "ret %i", ret);
424 void bch2_fs_btree_cache_init_early(struct btree_cache *bc)
426 mutex_init(&bc->lock);
427 INIT_LIST_HEAD(&bc->live);
428 INIT_LIST_HEAD(&bc->freeable);
429 INIT_LIST_HEAD(&bc->freed);
433 * We can only have one thread cannibalizing other cached btree nodes at a time,
434 * or we'll deadlock. We use an open coded mutex to ensure that, which a
435 * cannibalize_bucket() will take. This means every time we unlock the root of
436 * the btree, we need to release this lock if we have it held.
438 void bch2_btree_cache_cannibalize_unlock(struct bch_fs *c)
440 struct btree_cache *bc = &c->btree_cache;
442 if (bc->alloc_lock == current) {
443 trace_btree_node_cannibalize_unlock(c);
444 bc->alloc_lock = NULL;
445 closure_wake_up(&bc->alloc_wait);
449 int bch2_btree_cache_cannibalize_lock(struct bch_fs *c, struct closure *cl)
451 struct btree_cache *bc = &c->btree_cache;
452 struct task_struct *old;
454 old = cmpxchg(&bc->alloc_lock, NULL, current);
455 if (old == NULL || old == current)
459 trace_btree_node_cannibalize_lock_fail(c);
463 closure_wait(&bc->alloc_wait, cl);
465 /* Try again, after adding ourselves to waitlist */
466 old = cmpxchg(&bc->alloc_lock, NULL, current);
467 if (old == NULL || old == current) {
469 closure_wake_up(&bc->alloc_wait);
473 trace_btree_node_cannibalize_lock_fail(c);
477 trace_btree_node_cannibalize_lock(c);
481 static struct btree *btree_node_cannibalize(struct bch_fs *c)
483 struct btree_cache *bc = &c->btree_cache;
486 list_for_each_entry_reverse(b, &bc->live, list)
487 if (!btree_node_reclaim(c, b))
491 list_for_each_entry_reverse(b, &bc->live, list)
492 if (!btree_node_write_and_reclaim(c, b))
496 * Rare case: all nodes were intent-locked.
499 WARN_ONCE(1, "btree cache cannibalize failed\n");
504 struct btree *bch2_btree_node_mem_alloc(struct bch_fs *c)
506 struct btree_cache *bc = &c->btree_cache;
508 u64 start_time = local_clock();
510 mutex_lock(&bc->lock);
513 * btree_free() doesn't free memory; it sticks the node on the end of
514 * the list. Check if there's any freed nodes there:
516 list_for_each_entry(b, &bc->freeable, list)
517 if (!btree_node_reclaim(c, b))
521 * We never free struct btree itself, just the memory that holds the on
522 * disk node. Check the freed list before allocating a new one:
524 list_for_each_entry(b, &bc->freed, list)
525 if (!btree_node_reclaim(c, b)) {
526 btree_node_data_alloc(c, b, __GFP_NOWARN|GFP_NOIO);
530 six_unlock_write(&b->lock);
531 six_unlock_intent(&b->lock);
535 b = btree_node_mem_alloc(c, __GFP_NOWARN|GFP_NOIO);
539 BUG_ON(!six_trylock_intent(&b->lock));
540 BUG_ON(!six_trylock_write(&b->lock));
542 BUG_ON(btree_node_hashed(b));
543 BUG_ON(btree_node_write_in_flight(b));
545 list_del_init(&b->list);
546 mutex_unlock(&bc->lock);
553 b->whiteout_u64s = 0;
554 b->uncompacted_whiteout_u64s = 0;
555 bch2_btree_keys_init(b, &c->expensive_debug_checks);
557 bch2_time_stats_update(&c->times[BCH_TIME_btree_node_mem_alloc],
562 /* Try to cannibalize another cached btree node: */
563 if (bc->alloc_lock == current) {
564 b = btree_node_cannibalize(c);
565 list_del_init(&b->list);
566 mutex_unlock(&bc->lock);
568 bch2_btree_node_hash_remove(bc, b);
570 trace_btree_node_cannibalize(c);
574 mutex_unlock(&bc->lock);
575 return ERR_PTR(-ENOMEM);
578 /* Slowpath, don't want it inlined into btree_iter_traverse() */
579 static noinline struct btree *bch2_btree_node_fill(struct bch_fs *c,
580 struct btree_iter *iter,
581 const struct bkey_i *k,
583 enum six_lock_type lock_type,
586 struct btree_cache *bc = &c->btree_cache;
590 * Parent node must be locked, else we could read in a btree node that's
593 BUG_ON(!btree_node_locked(iter, level + 1));
594 BUG_ON(level >= BTREE_MAX_DEPTH);
596 b = bch2_btree_node_mem_alloc(c);
600 bkey_copy(&b->key, k);
601 if (bch2_btree_node_hash_insert(bc, b, level, iter->btree_id)) {
602 /* raced with another fill: */
604 /* mark as unhashed... */
605 bkey_i_to_extent(&b->key)->v._data[0] = 0;
607 mutex_lock(&bc->lock);
608 list_add(&b->list, &bc->freeable);
609 mutex_unlock(&bc->lock);
611 six_unlock_write(&b->lock);
612 six_unlock_intent(&b->lock);
617 * If the btree node wasn't cached, we can't drop our lock on
618 * the parent until after it's added to the cache - because
619 * otherwise we could race with a btree_split() freeing the node
620 * we're trying to lock.
622 * But the deadlock described below doesn't exist in this case,
623 * so it's safe to not drop the parent lock until here:
625 if (btree_node_read_locked(iter, level + 1))
626 btree_node_unlock(iter, level + 1);
628 bch2_btree_node_read(c, b, sync);
630 six_unlock_write(&b->lock);
633 six_unlock_intent(&b->lock);
637 if (lock_type == SIX_LOCK_read)
638 six_lock_downgrade(&b->lock);
644 * bch_btree_node_get - find a btree node in the cache and lock it, reading it
645 * in from disk if necessary.
647 * If IO is necessary and running under generic_make_request, returns -EAGAIN.
649 * The btree node will have either a read or a write lock held, depending on
650 * the @write parameter.
652 struct btree *bch2_btree_node_get(struct bch_fs *c, struct btree_iter *iter,
653 const struct bkey_i *k, unsigned level,
654 enum six_lock_type lock_type,
657 struct btree_cache *bc = &c->btree_cache;
662 * XXX: locking optimization
664 * we can make the locking looser here - caller can drop lock on parent
665 * node before locking child node (and potentially blocking): we just
666 * have to have bch2_btree_node_fill() call relock on the parent and
667 * return -EINTR if that fails
669 EBUG_ON(!btree_node_locked(iter, level + 1));
670 EBUG_ON(level >= BTREE_MAX_DEPTH);
673 b = btree_cache_find(bc, k);
678 * We must have the parent locked to call bch2_btree_node_fill(),
679 * else we could read in a btree node from disk that's been
682 b = bch2_btree_node_fill(c, iter, k, level, lock_type, true);
684 /* We raced and found the btree node in the cache */
692 * There's a potential deadlock with splits and insertions into
693 * interior nodes we have to avoid:
695 * The other thread might be holding an intent lock on the node
696 * we want, and they want to update its parent node so they're
697 * going to upgrade their intent lock on the parent node to a
700 * But if we're holding a read lock on the parent, and we're
701 * trying to get the intent lock they're holding, we deadlock.
703 * So to avoid this we drop the read locks on parent nodes when
704 * we're starting to take intent locks - and handle the race.
706 * The race is that they might be about to free the node we
707 * want, and dropping our read lock on the parent node lets them
708 * update the parent marking the node we want as freed, and then
711 * To guard against this, btree nodes are evicted from the cache
712 * when they're freed - and PTR_HASH() is zeroed out, which we
713 * check for after we lock the node.
715 * Then, bch2_btree_node_relock() on the parent will fail - because
716 * the parent was modified, when the pointer to the node we want
717 * was removed - and we'll bail out:
719 if (btree_node_read_locked(iter, level + 1))
720 btree_node_unlock(iter, level + 1);
722 if (!btree_node_lock(b, k->k.p, level, iter,
723 lock_type, may_drop_locks))
724 return ERR_PTR(-EINTR);
726 if (unlikely(PTR_HASH(&b->key) != PTR_HASH(k) ||
729 six_unlock_type(&b->lock, lock_type);
730 if (bch2_btree_node_relock(iter, level + 1))
734 return ERR_PTR(-EINTR);
738 wait_on_bit_io(&b->flags, BTREE_NODE_read_in_flight,
739 TASK_UNINTERRUPTIBLE);
741 prefetch(b->aux_data);
743 for_each_bset(b, t) {
744 void *p = (u64 *) b->aux_data + t->aux_data_offset;
746 prefetch(p + L1_CACHE_BYTES * 0);
747 prefetch(p + L1_CACHE_BYTES * 1);
748 prefetch(p + L1_CACHE_BYTES * 2);
751 /* avoid atomic set bit if it's not needed: */
752 if (btree_node_accessed(b))
753 set_btree_node_accessed(b);
755 if (unlikely(btree_node_read_error(b))) {
756 six_unlock_type(&b->lock, lock_type);
757 return ERR_PTR(-EIO);
760 EBUG_ON(b->btree_id != iter->btree_id ||
761 BTREE_NODE_LEVEL(b->data) != level ||
762 bkey_cmp(b->data->max_key, k->k.p));
767 struct btree *bch2_btree_node_get_sibling(struct bch_fs *c,
768 struct btree_iter *iter,
771 enum btree_node_sibling sib)
773 struct btree *parent;
774 struct btree_node_iter node_iter;
775 struct bkey_packed *k;
777 struct btree *ret = NULL;
778 unsigned level = b->level;
780 parent = btree_iter_node(iter, level + 1);
784 if (!bch2_btree_node_relock(iter, level + 1))
787 node_iter = iter->l[parent->level].iter;
789 k = bch2_btree_node_iter_peek_all(&node_iter, parent);
790 BUG_ON(bkey_cmp_left_packed(parent, k, &b->key.k.p));
792 k = sib == btree_prev_sib
793 ? bch2_btree_node_iter_prev(&node_iter, parent)
794 : (bch2_btree_node_iter_advance(&node_iter, parent),
795 bch2_btree_node_iter_peek(&node_iter, parent));
799 bch2_bkey_unpack(parent, &tmp.k, k);
801 ret = bch2_btree_node_get(c, iter, &tmp.k, level,
802 SIX_LOCK_intent, may_drop_locks);
804 if (PTR_ERR_OR_ZERO(ret) == -EINTR && may_drop_locks) {
805 struct btree_iter *linked;
807 if (!bch2_btree_node_relock(iter, level + 1))
811 * We might have got -EINTR because trylock failed, and we're
812 * holding other locks that would cause us to deadlock:
814 for_each_linked_btree_iter(iter, linked)
815 if (btree_iter_cmp(iter, linked) < 0)
816 __bch2_btree_iter_unlock(linked);
818 if (sib == btree_prev_sib)
819 btree_node_unlock(iter, level);
821 ret = bch2_btree_node_get(c, iter, &tmp.k, level,
822 SIX_LOCK_intent, may_drop_locks);
825 * before btree_iter_relock() calls btree_iter_verify_locks():
827 if (btree_lock_want(iter, level + 1) == BTREE_NODE_UNLOCKED)
828 btree_node_unlock(iter, level + 1);
830 if (!bch2_btree_node_relock(iter, level)) {
831 btree_iter_set_dirty(iter, BTREE_ITER_NEED_RELOCK);
834 six_unlock_intent(&ret->lock);
835 ret = ERR_PTR(-EINTR);
839 bch2_btree_iter_relock(iter);
842 if (btree_lock_want(iter, level + 1) == BTREE_NODE_UNLOCKED)
843 btree_node_unlock(iter, level + 1);
845 bch2_btree_iter_verify_locks(iter);
847 BUG_ON((!may_drop_locks || !IS_ERR(ret)) &&
848 (iter->uptodate >= BTREE_ITER_NEED_RELOCK ||
849 !btree_node_locked(iter, level)));
851 if (!IS_ERR_OR_NULL(ret)) {
852 struct btree *n1 = ret, *n2 = b;
854 if (sib != btree_prev_sib)
857 BUG_ON(bkey_cmp(btree_type_successor(n1->btree_id,
865 bch2_btree_iter_upgrade(iter, level + 2, true);
866 ret = ERR_PTR(-EINTR);
870 void bch2_btree_node_prefetch(struct bch_fs *c, struct btree_iter *iter,
871 const struct bkey_i *k, unsigned level)
873 struct btree_cache *bc = &c->btree_cache;
876 BUG_ON(!btree_node_locked(iter, level + 1));
877 BUG_ON(level >= BTREE_MAX_DEPTH);
880 b = btree_cache_find(bc, k);
886 bch2_btree_node_fill(c, iter, k, level, SIX_LOCK_read, false);
889 void bch2_btree_node_to_text(struct printbuf *out, struct bch_fs *c,
892 const struct bkey_format *f = &b->format;
893 struct bset_stats stats;
895 memset(&stats, 0, sizeof(stats));
897 bch2_btree_keys_stats(b, &stats);
900 "l %u %llu:%llu - %llu:%llu:\n"
903 b->data->min_key.inode,
904 b->data->min_key.offset,
905 b->data->max_key.inode,
906 b->data->max_key.offset);
907 bch2_val_to_text(out, c, BKEY_TYPE_BTREE,
908 bkey_i_to_s_c(&b->key));
910 " format: u64s %u fields %u %u %u %u %u\n"
911 " unpack fn len: %u\n"
912 " bytes used %zu/%zu (%zu%% full)\n"
913 " sib u64s: %u, %u (merge threshold %zu)\n"
914 " nr packed keys %u\n"
915 " nr unpacked keys %u\n"
917 " failed unpacked %zu\n"
919 " failed overflow %zu\n",
921 f->bits_per_field[0],
922 f->bits_per_field[1],
923 f->bits_per_field[2],
924 f->bits_per_field[3],
925 f->bits_per_field[4],
927 b->nr.live_u64s * sizeof(u64),
928 btree_bytes(c) - sizeof(struct btree_node),
929 b->nr.live_u64s * 100 / btree_max_u64s(c),
932 BTREE_FOREGROUND_MERGE_THRESHOLD(c),
936 stats.failed_unpacked,
938 stats.failed_overflow);