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bcachefs: Unlock in bch2_trans_begin() if we've held locks more than 10us

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We try to ensure we never hold btree locks for too long - bcachefs tries
to be soft realtime. This adds a check when restarting a transaction,
where a transaction restart is cheap - if we've been holding locks for
too long, drop and retake them.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
This commit is contained in:
Kent Overstreet 2022-07-13 06:03:21 -04:00 committed by Kent Overstreet
parent a1783320d4
commit 43de721a33
2 changed files with 12 additions and 1 deletions
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10
fs/bcachefs/btree_iter.c
View file

@ -3224,12 +3224,19 @@ void bch2_trans_begin(struct btree_trans *trans)
path->preserve = false;
}
bch2_trans_cond_resched(trans);
if (!trans->restarted &&
(need_resched() ||
ktime_get_ns() - trans->last_begin_time > BTREE_TRANS_MAX_LOCK_HOLD_TIME_NS)) {
bch2_trans_unlock(trans);
cond_resched();
bch2_trans_relock(trans);
}
if (trans->restarted)
bch2_btree_path_traverse_all(trans);
trans->restarted = false;
trans->last_begin_time = ktime_get_ns();
}
static void bch2_trans_alloc_paths(struct btree_trans *trans, struct bch_fs *c)
@ -3259,6 +3266,7 @@ void __bch2_trans_init(struct btree_trans *trans, struct bch_fs *c,
memset(trans, 0, sizeof(*trans));
trans->c = c;
trans->fn = fn;
trans->last_begin_time = ktime_get_ns();
trans->task = current;
trans->journal_replay_not_finished =
!test_bit(JOURNAL_REPLAY_DONE, &c->journal.flags);

3
fs/bcachefs/btree_types.h
View file

@ -382,10 +382,13 @@ struct btree_trans_commit_hook {
#define BTREE_TRANS_MEM_MAX (1U << 16)
#define BTREE_TRANS_MAX_LOCK_HOLD_TIME_NS 10000
struct btree_trans {
struct bch_fs *c;
const char *fn;
struct list_head list;
u64 last_begin_time;
struct btree *locking;
unsigned locking_path_idx;
struct bpos locking_pos;