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bcache: don't set max writeback rate if gc is running 

When gc is running, user space I/O processes may wait inside
bcache code, so no new I/O coming. Indeed this is not a real idle
time, maximum writeback rate should not be set in such situation.
Otherwise a faster writeback thread may compete locks with gc thread
and makes garbage collection slower, which results a longer I/O
freeze period.

This patch checks c->gc_mark_valid in set_at_max_writeback_rate(). If
c->gc_mark_valid is 0 (gc running), set_at_max_writeback_rate() returns
false, then update_writeback_rate() will not set writeback rate to
maximum value even c->idle_counter reaches an idle threshold.

Now writeback thread won't interfere gc thread performance.

Signed-off-by: Coly Li <colyli@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Coly Li 2019-06-28 19:59:24 +08:00 committed by Jens Axboe
parent a5b47a40be
commit 141df8bb5d
1 changed files with 3 additions and 0 deletions
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3
drivers/md/bcache/writeback.c
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@ -122,6 +122,9 @@ static void __update_writeback_rate(struct cached_dev *dc)
static bool set_at_max_writeback_rate(struct cache_set *c,
struct cached_dev *dc)
{
/* Don't set max writeback rate if gc is running */
if (!c->gc_mark_valid)
return false;
/*
* Idle_counter is increased everytime when update_writeback_rate() is
* called. If all backing devices attached to the same cache set have