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[73.71.82.80]) by smtp.gmail.com with ESMTPSA id f80sm13989754pfa.160.2021.05.25.14.25.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 25 May 2021 14:25:43 -0700 (PDT) From: Benjamin Segall To: Peter Zijlstra Cc: changhuaixin , Dietmar Eggemann , dtcccc@linux.alibaba.com, Juri Lelli , khlebnikov@yandex-team.ru, open list , Mel Gorman , Ingo Molnar , Odin Ugedal , Odin Ugedal , pauld@redhead.com, Paul Turner , Steven Rostedt , Shanpei Chen , Tejun Heo , Vincent Guittot , xiyou.wangcong@gmail.com Subject: Re: [PATCH v5 1/3] sched/fair: Introduce the burstable CFS controller References: <20210520123419.8039-1-changhuaixin@linux.alibaba.com> <20210520123419.8039-2-changhuaixin@linux.alibaba.com> Date: Tue, 25 May 2021 14:25:33 -0700 In-Reply-To: (Peter Zijlstra's message of "Tue, 25 May 2021 12:47:23 +0200") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Peter Zijlstra writes: > On Mon, May 24, 2021 at 08:42:03PM +0800, changhuaixin wrote: > >> >> static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg) >> >> @@ -4651,6 +4666,9 @@ static int __assign_cfs_rq_runtime(struct cfs_bandwidth *cfs_b, >> >> if (cfs_b->quota == RUNTIME_INF) >> >> amount = min_amount; >> >> else { >> >> + if (!cfs_b->period_active) >> >> + __refill_cfs_bandwidth_runtime(cfs_b); >> > >> > Why this call? >> >> As the cfs bandwidth timer stops on idle with runtime unfilled, refill runtime when it restarts to make >> use of the underrun when period timer stops. Another way to do this might be: >> >> throttled = !list_empty(&cfs_b->throttled_cfs_rq); >> cfs_b->nr_periods += overrun; >> >> + __refill_cfs_bandwidth_runtime(cfs_b); >> + >> /* >> * idle depends on !throttled (for the case of a large deficit), and if >> * we're going inactive then everything else can be deferred >> */ >> if (cfs_b->idle && !throttled) >> goto out_deactivate; >> >> - __refill_cfs_bandwidth_runtime(cfs_b); >> - >> if (!throttled) { >> > > Ben, do you have a preference? I think I prefer the latter, possibly with a /* Refill extra burst quota even if cfs_b->idle */