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| author | Shaohua Li <shli@fb.com> | 2017-03-27 19:51:36 +0200 |
|---|---|---|
| committer | Jens Axboe <axboe@fb.com> | 2017-03-28 16:02:20 +0200 |
| commit | 06cceedcca67a93ac7f7aa93bbd9980c7496d14e (patch) | |
| tree | af55df52adb802cb6dc7e63068165a4b8ccfc4d2 /block/blk-throttle.c | |
| parent | blk-throttle: add downgrade logic (diff) | |
| download | linux-06cceedcca67a93ac7f7aa93bbd9980c7496d14e.tar.xz linux-06cceedcca67a93ac7f7aa93bbd9980c7496d14e.zip | |
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 <shli@fb.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'block/blk-throttle.c')
| -rw-r--r-- | block/blk-throttle.c | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/block/blk-throttle.c b/block/blk-throttle.c index 7878ec1ed5e8..2073b4839ba5 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); |