| Message ID | 977d7661612aa15e1647690dd2d450ab5e3db1a6.1481833017.git.shli@fb.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu, Dec 15, 2016 at 12:32:58PM -0800, Shaohua Li wrote: > 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 <shli@fb.com> > --- > block/blk-throttle.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/block/blk-throttle.c b/block/blk-throttle.c > index 0f65fce..41ec72c 100644 > --- a/block/blk-throttle.c > +++ b/block/blk-throttle.c > @@ -588,6 +588,10 @@ 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; > + > + if (time_after(expires, max_expire)) > + expires = max_expire; A comment explaining why we need this would be nice. Thanks.
diff --git a/block/blk-throttle.c b/block/blk-throttle.c index 0f65fce..41ec72c 100644 --- a/block/blk-throttle.c +++ b/block/blk-throttle.c @@ -588,6 +588,10 @@ 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; + + 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);
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 <shli@fb.com> --- block/blk-throttle.c | 4 ++++ 1 file changed, 4 insertions(+)