From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, UNPARSEABLE_RELAY autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7A3E4C04AB5 for ; Thu, 6 Jun 2019 14:11:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5B6AB20673 for ; Thu, 6 Jun 2019 14:11:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728011AbfFFOLl (ORCPT ); Thu, 6 Jun 2019 10:11:41 -0400 Received: from out30-130.freemail.mail.aliyun.com ([115.124.30.130]:35153 "EHLO out30-130.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726092AbfFFOLl (ORCPT ); Thu, 6 Jun 2019 10:11:41 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R171e4;CH=green;DM=||false|;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e07486;MF=xlpang@linux.alibaba.com;NM=1;PH=DS;RN=5;SR=0;TI=SMTPD_---0TTaIHVa_1559830289; Received: from xunleideMacBook-Pro.local(mailfrom:xlpang@linux.alibaba.com fp:SMTPD_---0TTaIHVa_1559830289) by smtp.aliyun-inc.com(127.0.0.1); Thu, 06 Jun 2019 22:11:30 +0800 Reply-To: xlpang@linux.alibaba.com Subject: Re: [PATCH] sched/fair: don't push cfs_bandwith slack timers forward To: bsegall@google.com, linux-kernel@vger.kernel.org, Peter Zijlstra Cc: Ingo Molnar , Phil Auld References: From: Xunlei Pang Message-ID: Date: Thu, 6 Jun 2019 22:11:29 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=gbk Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2019/6/6 AM 4:06, bsegall@google.com wrote: > When a cfs_rq sleeps and returns its quota, we delay for 5ms before > waking any throttled cfs_rqs to coalesce with other cfs_rqs going to > sleep, as this has has to be done outside of the rq lock we hold. two "has". > > The current code waits for 5ms without any sleeps, instead of waiting > for 5ms from the first sleep, which can delay the unthrottle more than > we want. Switch this around so that we can't push this forward forever. > > This requires an extra flag rather than using hrtimer_active, since we > need to start a new timer if the current one is in the process of > finishing. > > Signed-off-by: Ben Segall > --- We've also suffered from this performance issue recently: Reviewed-by: Xunlei Pang > kernel/sched/fair.c | 7 +++++++ > kernel/sched/sched.h | 1 + > 2 files changed, 8 insertions(+) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 8213ff6e365d..2ead252cfa32 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -4729,6 +4729,11 @@ static void start_cfs_slack_bandwidth(struct cfs_bandwidth *cfs_b) > if (runtime_refresh_within(cfs_b, min_left)) > return; > > + /* don't push forwards an existing deferred unthrottle */ > + if (cfs_b->slack_started) > + return; > + cfs_b->slack_started = true; > + > hrtimer_start(&cfs_b->slack_timer, > ns_to_ktime(cfs_bandwidth_slack_period), > HRTIMER_MODE_REL); > @@ -4782,6 +4787,7 @@ static void do_sched_cfs_slack_timer(struct cfs_bandwidth *cfs_b) > > /* confirm we're still not at a refresh boundary */ > raw_spin_lock_irqsave(&cfs_b->lock, flags); > + cfs_b->slack_started = false; > if (cfs_b->distribute_running) { > raw_spin_unlock_irqrestore(&cfs_b->lock, flags); > return; > @@ -4920,6 +4926,7 @@ void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) > hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); > cfs_b->slack_timer.function = sched_cfs_slack_timer; > cfs_b->distribute_running = 0; > + cfs_b->slack_started = false; > } > > static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) > diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h > index efa686eeff26..60219acda94b 100644 > --- a/kernel/sched/sched.h > +++ b/kernel/sched/sched.h > @@ -356,6 +356,7 @@ struct cfs_bandwidth { > u64 throttled_time; > > bool distribute_running; > + bool slack_started; > #endif > }; > >