From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:48048 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1031100AbeCSSVU (ORCPT ); Mon, 19 Mar 2018 14:21:20 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Shaohua Li , Jens Axboe , Sasha Levin Subject: [PATCH 4.9 078/241] blk-throttle: make sure expire time isnt too big Date: Mon, 19 Mar 2018 19:05:43 +0100 Message-Id: <20180319180754.432758367@linuxfoundation.org> In-Reply-To: <20180319180751.172155436@linuxfoundation.org> References: <20180319180751.172155436@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Shaohua Li [ 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 Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- block/blk-throttle.c | 11 +++++++++++ 1 file changed, 11 insertions(+) --- a/block/blk-throttle.c +++ b/block/blk-throttle.c @@ -499,6 +499,17 @@ static void throtl_dequeue_tg(struct thr 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);