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bcachefs: Avoid flushing the journal in the discard path

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When issuing discards, we may need to flush the journal if there's too
many buckets that can't be discarded until a journal flush.

But the heuristic was bad; we should be comparing the number of buckets
that need to flushes against the number of free buckets, not the number
of buckets we saw.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet 2024-01-15 17:56:22 -05:00
parent 189c176c5d
commit a6548c8b5e
1 changed files with 41 additions and 19 deletions
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60
fs/bcachefs/alloc_background.c
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@ -1604,13 +1604,36 @@ int bch2_check_alloc_to_lru_refs(struct bch_fs *c)
return ret; return ret;
} }
struct discard_buckets_state {
u64 seen;
u64 open;
u64 need_journal_commit;
u64 discarded;
struct bch_dev *ca;
u64 need_journal_commit_this_dev;
};
static void discard_buckets_next_dev(struct bch_fs *c, struct discard_buckets_state *s, struct bch_dev *ca)
{
if (s->ca == ca)
return;
if (s->ca && s->need_journal_commit_this_dev >
bch2_dev_usage_read(s->ca).d[BCH_DATA_free].buckets)
bch2_journal_flush_async(&c->journal, NULL);
if (s->ca)
percpu_ref_put(&s->ca->ref);
if (ca)
percpu_ref_get(&ca->ref);
s->ca = ca;
s->need_journal_commit_this_dev = 0;
}
static int bch2_discard_one_bucket(struct btree_trans *trans, static int bch2_discard_one_bucket(struct btree_trans *trans,
struct btree_iter *need_discard_iter, struct btree_iter *need_discard_iter,
struct bpos *discard_pos_done, struct bpos *discard_pos_done,
u64 *seen, struct discard_buckets_state *s)
u64 *open,
u64 *need_journal_commit,
u64 *discarded)
{ {
struct bch_fs *c = trans->c; struct bch_fs *c = trans->c;
struct bpos pos = need_discard_iter->pos; struct bpos pos = need_discard_iter->pos;
@ -1622,20 +1645,24 @@ static int bch2_discard_one_bucket(struct btree_trans *trans,
int ret = 0; int ret = 0;
ca = bch_dev_bkey_exists(c, pos.inode); ca = bch_dev_bkey_exists(c, pos.inode);
if (!percpu_ref_tryget(&ca->io_ref)) { if (!percpu_ref_tryget(&ca->io_ref)) {
bch2_btree_iter_set_pos(need_discard_iter, POS(pos.inode + 1, 0)); bch2_btree_iter_set_pos(need_discard_iter, POS(pos.inode + 1, 0));
return 0; return 0;
} }
discard_buckets_next_dev(c, s, ca);
if (bch2_bucket_is_open_safe(c, pos.inode, pos.offset)) { if (bch2_bucket_is_open_safe(c, pos.inode, pos.offset)) {
(*open)++; s->open++;
goto out; goto out;
} }
if (bch2_bucket_needs_journal_commit(&c->buckets_waiting_for_journal, if (bch2_bucket_needs_journal_commit(&c->buckets_waiting_for_journal,
c->journal.flushed_seq_ondisk, c->journal.flushed_seq_ondisk,
pos.inode, pos.offset)) { pos.inode, pos.offset)) {
(*need_journal_commit)++; s->need_journal_commit++;
s->need_journal_commit_this_dev++;
goto out; goto out;
} }
@ -1711,9 +1738,9 @@ write:
goto out; goto out;
count_event(c, bucket_discard); count_event(c, bucket_discard);
(*discarded)++; s->discarded++;
out: out:
(*seen)++; s->seen++;
bch2_trans_iter_exit(trans, &iter); bch2_trans_iter_exit(trans, &iter);
percpu_ref_put(&ca->io_ref); percpu_ref_put(&ca->io_ref);
printbuf_exit(&buf); printbuf_exit(&buf);
@ -1723,7 +1750,7 @@ out:
static void bch2_do_discards_work(struct work_struct *work) static void bch2_do_discards_work(struct work_struct *work)
{ {
struct bch_fs *c = container_of(work, struct bch_fs, discard_work); struct bch_fs *c = container_of(work, struct bch_fs, discard_work);
u64 seen = 0, open = 0, need_journal_commit = 0, discarded = 0; struct discard_buckets_state s = {};
struct bpos discard_pos_done = POS_MAX; struct bpos discard_pos_done = POS_MAX;
int ret; int ret;
@ -1735,19 +1762,14 @@ static void bch2_do_discards_work(struct work_struct *work)
ret = bch2_trans_run(c, ret = bch2_trans_run(c,
for_each_btree_key(trans, iter, for_each_btree_key(trans, iter,
BTREE_ID_need_discard, POS_MIN, 0, k, BTREE_ID_need_discard, POS_MIN, 0, k,
bch2_discard_one_bucket(trans, &iter, &discard_pos_done, bch2_discard_one_bucket(trans, &iter, &discard_pos_done, &s)));
&seen,
&open,
&need_journal_commit,
&discarded)));
if (need_journal_commit * 2 > seen) discard_buckets_next_dev(c, &s, NULL);
bch2_journal_flush_async(&c->journal, NULL);
trace_discard_buckets(c, s.seen, s.open, s.need_journal_commit, s.discarded,
bch2_err_str(ret));
bch2_write_ref_put(c, BCH_WRITE_REF_discard); bch2_write_ref_put(c, BCH_WRITE_REF_discard);
trace_discard_buckets(c, seen, open, need_journal_commit, discarded,
bch2_err_str(ret));
} }
void bch2_do_discards(struct bch_fs *c) void bch2_do_discards(struct bch_fs *c)