From c2a4f3183a1248f615a695fbd8905da55ad11bba Mon Sep 17 00:00:00 2001 From: Kent Overstreet Date: Mon, 23 Sep 2013 23:17:31 -0700 Subject: bcache: Fix a writeback performance regression Background writeback works by scanning the btree for dirty data and adding those keys into a fixed size buffer, then for each dirty key in the keybuf writing it to the backing device. When read_dirty() finishes and it's time to scan for more dirty data, we need to wait for the outstanding writeback IO to finish - they still take up slots in the keybuf (so that foreground writes can check for them to avoid races) - without that wait, we'll continually rescan when we'll be able to add at most a key or two to the keybuf, and that takes locks that starves foreground IO. Doh. Signed-off-by: Kent Overstreet Cc: linux-stable # >= v3.10 Signed-off-by: Linus Torvalds --- drivers/md/bcache/util.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) (limited to 'drivers/md/bcache/util.c') diff --git a/drivers/md/bcache/util.c b/drivers/md/bcache/util.c index 98eb81159a22..420dad545c7d 100644 --- a/drivers/md/bcache/util.c +++ b/drivers/md/bcache/util.c @@ -190,7 +190,16 @@ void bch_time_stats_update(struct time_stats *stats, uint64_t start_time) stats->last = now ?: 1; } -unsigned bch_next_delay(struct ratelimit *d, uint64_t done) +/** + * bch_next_delay() - increment @d by the amount of work done, and return how + * long to delay until the next time to do some work. + * + * @d - the struct bch_ratelimit to update + * @done - the amount of work done, in arbitrary units + * + * Returns the amount of time to delay by, in jiffies + */ +uint64_t bch_next_delay(struct bch_ratelimit *d, uint64_t done) { uint64_t now = local_clock(); -- cgit v1.2.3