diff options
Diffstat (limited to 'drivers/md/bcache/writeback.c')
| -rw-r--r-- | drivers/md/bcache/writeback.c | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c index 6e1d2fde43df..f82ffb2e9b9b 100644 --- a/drivers/md/bcache/writeback.c +++ b/drivers/md/bcache/writeback.c @@ -356,6 +356,27 @@ static void read_dirty(struct cached_dev *dc) delay = writeback_delay(dc, size); + /* If the control system would wait for at least half a + * second, and there's been no reqs hitting the backing disk + * for awhile: use an alternate mode where we have at most + * one contiguous set of writebacks in flight at a time. If + * someone wants to do IO it will be quick, as it will only + * have to contend with one operation in flight, and we'll + * be round-tripping data to the backing disk as quickly as + * it can accept it. + */ + if (delay >= HZ / 2) { + /* 3 means at least 1.5 seconds, up to 7.5 if we + * have slowed way down. + */ + if (atomic_inc_return(&dc->backing_idle) >= 3) { + /* Wait for current I/Os to finish */ + closure_sync(&cl); + /* And immediately launch a new set. */ + delay = 0; + } + } + while (!kthread_should_stop() && delay) { schedule_timeout_interruptible(delay); delay = writeback_delay(dc, 0); |