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@xxxxxxx>
---
drivers/md/bcache/writeback.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c
index 73f0efac2b9f..262f7ef20992 100644
--- a/drivers/md/bcache/writeback.c
+++ b/drivers/md/bcache/writeback.c
@@ -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
--
2.16.4
