path: root/block/blk-throttle.c
diff options
authorShaohua Li <>2017-03-27 10:51:36 -0700
committerJens Axboe <>2017-03-28 08:02:20 -0600
commit06cceedcca67a93ac7f7aa93bbd9980c7496d14e (patch)
treeaf55df52adb802cb6dc7e63068165a4b8ccfc4d2 /block/blk-throttle.c
parent3f0abd806651df546f426f23490fec997dc87e5b (diff)
blk-throttle: make sure expire time isn't too big
cgroup could be throttled to a limit but when all cgroups cross high limit, queue enters a higher state and so the group should be throttled to a higher limit. It's possible the cgroup is sleeping because of throttle and other cgroups don't dispatch IO any more. In this case, nobody can trigger current downgrade/upgrade logic. To fix this issue, we could either set up a timer to wakeup the cgroup if other cgroups are idle or make sure this cgroup doesn't sleep too long. Setting up a timer means we must change the timer very frequently. This patch chooses the latter. Making cgroup sleep time not too big wouldn't change cgroup bps/iops, but could make it wakeup more frequently, which isn't a big issue because throtl_slice * 8 is already quite big. Signed-off-by: Shaohua Li <> Signed-off-by: Jens Axboe <>
Diffstat (limited to 'block/blk-throttle.c')
1 files changed, 11 insertions, 0 deletions
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 7878ec1..2073b48 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -590,6 +590,17 @@ static void throtl_dequeue_tg(struct throtl_grp *tg)
static void throtl_schedule_pending_timer(struct throtl_service_queue *sq,
unsigned long expires)
+ unsigned long max_expire = jiffies + 8 * throtl_slice;
+ /*
+ * Since we are adjusting the throttle limit dynamically, the sleep
+ * time calculated according to previous limit might be invalid. It's
+ * possible the cgroup sleep time is very long and no other cgroups
+ * have IO running so notify the limit changes. Make sure the cgroup
+ * doesn't sleep too long to avoid the missed notification.
+ */
+ if (time_after(expires, max_expire))
+ expires = max_expire;
mod_timer(&sq->pending_timer, expires);
throtl_log(sq, "schedule timer. delay=%lu jiffies=%lu",
expires - jiffies, jiffies);