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Code Issues Releases Wiki Activity

bcachefs: Improve btree key cache shrinker

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The shrinker should start scanning for entries that can be freed oldest
to newest - this way, we can avoid scanning a lot of entries that are
too new to be freed.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet 2020-11-19 15:38:27 -05:00 committed by Kent Overstreet
parent 4e92cbb642
commit 125907203c
2 changed files with 49 additions and 50 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

95
fs/bcachefs/btree_key_cache.c
View file

@ -78,10 +78,13 @@ static void bkey_cached_free(struct btree_key_cache *bc,
{
struct bch_fs *c = container_of(bc, struct bch_fs, btree_key_cache);
BUG_ON(test_bit(BKEY_CACHED_DIRTY, &ck->flags));
ck->btree_trans_barrier_seq =
start_poll_synchronize_srcu(&c->btree_trans_barrier);
list_move(&ck->list, &bc->freed);
list_move_tail(&ck->list, &bc->freed);
bc->nr_freed++;
kfree(ck->k);
ck->k = NULL;
@ -96,9 +99,21 @@ bkey_cached_alloc(struct btree_key_cache *c)
{
struct bkey_cached *ck;
list_for_each_entry(ck, &c->freed, list)
if (bkey_cached_lock_for_evict(ck))
list_for_each_entry_reverse(ck, &c->freed, list)
if (bkey_cached_lock_for_evict(ck)) {
c->nr_freed--;
return ck;
}
ck = kmem_cache_alloc(bch2_key_cache, GFP_NOFS|__GFP_ZERO);
if (likely(ck)) {
INIT_LIST_HEAD(&ck->list);
six_lock_init(&ck->c.lock);
lockdep_set_novalidate_class(&ck->c.lock);
BUG_ON(!six_trylock_intent(&ck->c.lock));
BUG_ON(!six_trylock_write(&ck->c.lock));
return ck;
}
list_for_each_entry(ck, &c->clean, list)
if (bkey_cached_lock_for_evict(ck)) {
@ -106,17 +121,7 @@ bkey_cached_alloc(struct btree_key_cache *c)
return ck;
}
ck = kmem_cache_alloc(bch2_key_cache, GFP_NOFS|__GFP_ZERO);
if (!ck)
return NULL;
INIT_LIST_HEAD(&ck->list);
six_lock_init(&ck->c.lock);
lockdep_set_novalidate_class(&ck->c.lock);
BUG_ON(!six_trylock_intent(&ck->c.lock));
BUG_ON(!six_trylock_write(&ck->c.lock));
return ck;
return NULL;
}
static struct bkey_cached *
@ -135,8 +140,7 @@ btree_key_cache_create(struct btree_key_cache *c,
ck->key.btree_id = btree_id;
ck->key.pos = pos;
ck->valid = false;
BUG_ON(ck->flags);
ck->flags = 1U << BKEY_CACHED_ACCESSED;
if (rhashtable_lookup_insert_fast(&c->table,
&ck->hash,
@ -293,6 +297,9 @@ int bch2_btree_iter_traverse_cached(struct btree_iter *iter)
goto err;
}
if (!test_bit(BKEY_CACHED_ACCESSED, &ck->flags))
set_bit(BKEY_CACHED_ACCESSED, &ck->flags);
iter->uptodate = BTREE_ITER_NEED_PEEK;
bch2_btree_iter_downgrade(iter);
return ret;
@ -512,28 +519,34 @@ static unsigned long bch2_btree_key_cache_scan(struct shrinker *shrink,
flags = memalloc_nofs_save();
/*
* Newest freed entries are at the end of the list - once we hit one
* that's too new to be freed, we can bail out:
*/
list_for_each_entry_safe(ck, t, &bc->freed, list) {
if (!poll_state_synchronize_srcu(&c->btree_trans_barrier,
ck->btree_trans_barrier_seq))
break;
list_del(&ck->list);
kmem_cache_free(bch2_key_cache, ck);
bc->nr_freed--;
scanned++;
if (poll_state_synchronize_srcu(&c->btree_trans_barrier,
ck->btree_trans_barrier_seq)) {
list_del(&ck->list);
kmem_cache_free(bch2_key_cache, ck);
freed++;
}
if (scanned >= nr)
goto out;
freed++;
}
list_for_each_entry_safe(ck, t, &bc->clean, list) {
scanned++;
if (scanned >= nr)
goto out;
if (bkey_cached_lock_for_evict(ck)) {
list_for_each_entry_safe(ck, t, &bc->clean, list) {
if (test_bit(BKEY_CACHED_ACCESSED, &ck->flags))
clear_bit(BKEY_CACHED_ACCESSED, &ck->flags);
else if (bkey_cached_lock_for_evict(ck)) {
bkey_cached_evict(bc, ck);
bkey_cached_free(bc, ck);
}
scanned++;
if (scanned >= nr) {
if (&t->list != &bc->clean)
list_move_tail(&bc->clean, &t->list);
@ -602,6 +615,7 @@ int bch2_fs_btree_key_cache_init(struct btree_key_cache *bc)
{
struct bch_fs *c = container_of(bc, struct bch_fs, btree_key_cache);
bc->shrink.seeks = 1;
bc->shrink.count_objects = bch2_btree_key_cache_count;
bc->shrink.scan_objects = bch2_btree_key_cache_scan;
@ -611,26 +625,9 @@ int bch2_fs_btree_key_cache_init(struct btree_key_cache *bc)
void bch2_btree_key_cache_to_text(struct printbuf *out, struct btree_key_cache *c)
{
struct bucket_table *tbl;
struct bkey_cached *ck;
struct rhash_head *pos;
size_t i;
mutex_lock(&c->lock);
tbl = rht_dereference_rcu(c->table.tbl, &c->table);
for (i = 0; i < tbl->size; i++) {
rht_for_each_entry_rcu(ck, pos, tbl, i, hash) {
pr_buf(out, "%s:",
bch2_btree_ids[ck->key.btree_id]);
bch2_bpos_to_text(out, ck->key.pos);
if (test_bit(BKEY_CACHED_DIRTY, &ck->flags))
pr_buf(out, " journal seq %llu", ck->journal.seq);
pr_buf(out, "\n");
}
}
mutex_unlock(&c->lock);
pr_buf(out, "nr_freed:\t%zu\n", c->nr_freed);
pr_buf(out, "nr_keys:\t%zu\n", c->nr_keys);
pr_buf(out, "nr_dirty:\t%zu\n", c->nr_dirty);
}
void bch2_btree_key_cache_exit(void)

4
fs/bcachefs/btree_types.h
View file

@ -298,6 +298,7 @@ struct btree_key_cache {
struct list_head dirty;
struct shrinker shrink;
size_t nr_freed;
size_t nr_keys;
size_t nr_dirty;
};
@ -307,7 +308,8 @@ struct bkey_cached_key {
struct bpos pos;
} __attribute__((packed, aligned(4)));
#define BKEY_CACHED_DIRTY 0
#define BKEY_CACHED_ACCESSED 0
#define BKEY_CACHED_DIRTY 1
struct bkey_cached {
struct btree_bkey_cached_common c;