Commit 141df8bb authored Jun 28, 2019 by Coly Li Committed by Jens Axboe Jun 28, 2019

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>

parent a5b47a40

drivers/md/bcache/writeback.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -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

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