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authorShaohua Li <shli@fb.com>2017-03-27 10:51:36 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2018-03-22 09:23:22 +0100
commitfc23c57dbf90e2c9d5e1e394def93b4d2f190dbd (patch)
tree9c236a86543c6648cbe1c668dd2e719a107edb25 /block
parent610c3618669fd609d4ed2c199d64b26f1e41549a (diff)
blk-throttle: make sure expire time isn't too big
[ Upstream commit 06cceedcca67a93ac7f7aa93bbd9980c7496d14e ] 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> Signed-off-by: Sasha Levin <alexander.levin@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'block')
-rw-r--r--block/blk-throttle.c11
1 files changed, 11 insertions, 0 deletions
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 2149a1ddbacf..17bdd6b55beb 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -505,6 +505,17 @@ 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);