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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 92FDEC3A5A0 for ; Mon, 19 Aug 2019 17:34:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 708D022CE8 for ; Mon, 19 Aug 2019 17:34:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727988AbfHSReR (ORCPT ); Mon, 19 Aug 2019 13:34:17 -0400 Received: from foss.arm.com ([217.140.110.172]:57838 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726905AbfHSReR (ORCPT ); Mon, 19 Aug 2019 13:34:17 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 5EA4A360; Mon, 19 Aug 2019 10:34:16 -0700 (PDT) Received: from [10.1.194.37] (e113632-lin.cambridge.arm.com [10.1.194.37]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 351333F246; Mon, 19 Aug 2019 10:34:15 -0700 (PDT) Subject: Re: [PATCH] sched/fair: don't assign runtime for throttled cfs_rq From: Valentin Schneider To: Liangyan Cc: Ingo Molnar , Peter Zijlstra , linux-kernel@vger.kernel.org, shanpeic@linux.alibaba.com, xlpang@linux.alibaba.com, pjt@google.com References: <20190814180021.165389-1-liangyan.peng@linux.alibaba.com> <2994a6ee-9238-5285-3227-cb7084a834c8@arm.com> <7C1833A8-27A4-4755-9B1E-335C20207A66@linux.alibaba.com> <39d1affb-9cfa-208d-8bf4-f4c802e8c7f9@arm.com> <02BC41EE-6653-4473-91D4-CDEE53D8703D@linux.alibaba.com> Message-ID: <0004fb54-cdee-2197-1cbf-6e2111d39ed9@arm.com> Date: Mon, 19 Aug 2019 18:34:13 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=gbk Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 16/08/2019 18:19, Valentin Schneider wrote: [...] > Yeah it's probably pretty stupid. IIRC throttled cfs_rq means frozen > rq_clock, so any subsequent call to update_curr() on a throttled cfs_rq > should lead to an early bailout anyway due to delta_exec <= 0. > Did some more tracing, seems like the issue is we can make ->runtime_remaining positive in assign_cfs_rq_runtime() but not mark the cfs_rq as unthrottled. So AFAICT we'd need something like this: -----8<----- diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 1054d2cf6aaa..ffbb4dfc4b81 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4385,6 +4385,11 @@ static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq) return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time; } +static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq) +{ + return cfs_bandwidth_used() && cfs_rq->throttled; +} + /* returns 0 on failure to allocate runtime */ static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq) { @@ -4411,6 +4416,9 @@ static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq) cfs_rq->runtime_remaining += amount; + if (cfs_rq->runtime_remaining > 0 && cfs_rq_throttled(cfs_rq)) + unthrottle_cfs_rq(cfs_rq); + return cfs_rq->runtime_remaining > 0; } @@ -4439,11 +4447,6 @@ void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) __account_cfs_rq_runtime(cfs_rq, delta_exec); } -static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq) -{ - return cfs_bandwidth_used() && cfs_rq->throttled; -} - /* check whether cfs_rq, or any parent, is throttled */ static inline int throttled_hierarchy(struct cfs_rq *cfs_rq) { ----->8----- Does that make sense? If so we *may* want to add some ->runtime_remaining wrappers (e.g. {add/remove}_runtime()) and have the check in there to make sure it's not forgotten.