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bh=89iz/MxDzahCL/GLnt/CKfUxUo8O84OAzdIjlZFZ7g8=; b=VGfzmGH+U6l1FSSfwNPaIHuJvJX/14XcZR6YWXn8ou/EEvH+t26GdVM7H+BYKKIEsp olgoftucUVHvZezCqMqF2GwMlW9mIGMGSnPwU056AnisPKxuTJt0Wk/uK55sDrw0LNFp pQjVwucukPsFXWFPsgTgo7JWk4JFGfJUto+J0+bOx+0uo1QJzfH0zxDDXZluA6DBbPMv NdagEuXsjWjazD2QTs0Hqy35T8eR5alq2ZCRP+TM0Uz7vma1x0IOcUw4vWzhATrO5s0M Yobb++Yi+fFp//zATTTHdhrlHG+x0X+tjhj9BpEe1KjaA1evfDcas5pVv1EWEqyVnzQi cYuw== X-Gm-Message-State: AOAM530i0W8OiFWSuk3rFS7cP+cJosxjWhjOo4JdkUk86rd3PRl7vVsZ /6JztS5mhyz2IwE1jjTXEoXSe/XZF/b2nL/6C649vw== X-Google-Smtp-Source: ABdhPJyoVHirq6CcJFwkQEBzUDrKScJ7V8BH/zPmx4u3EL9V1Yxac0gXOMltOX/HG9NAlRotLr4Jl/kyb4QGE0RL6So= X-Received: by 2002:a05:6512:3385:: with SMTP id h5mr28656817lfg.154.1629791780173; Tue, 24 Aug 2021 00:56:20 -0700 (PDT) MIME-Version: 1.0 References: <20210820010403.946838-1-joshdon@google.com> <20210820010403.946838-4-joshdon@google.com> In-Reply-To: From: Vincent Guittot Date: Tue, 24 Aug 2021 09:56:09 +0200 Message-ID: Subject: Re: [PATCH v3 3/4] sched: reduce sched slice for SCHED_IDLE entities To: Josh Don Cc: Ingo Molnar , Peter Zijlstra , Juri Lelli , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Paul Turner , Oleg Rombakh , Viresh Kumar , Steve Sistare , Tejun Heo , Rik van Riel , linux-kernel Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 23 Aug 2021 at 19:40, Josh Don wrote: > > On Mon, Aug 23, 2021 at 3:08 AM Vincent Guittot > wrote: > > > > On Fri, 20 Aug 2021 at 03:04, Josh Don wrote: > > > > > > @@ -684,12 +696,13 @@ static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se) > > > for_each_sched_entity(se) { > > > struct load_weight *load; > > > struct load_weight lw; > > > + struct cfs_rq *qcfs_rq; > > > > > > - cfs_rq = cfs_rq_of(se); > > > - load = &cfs_rq->load; > > > + qcfs_rq = cfs_rq_of(se); > > > + load = &qcfs_rq->load; > > > > > > if (unlikely(!se->on_rq)) { > > > - lw = cfs_rq->load; > > > + lw = qcfs_rq->load; > > > > > > update_load_add(&lw, se->load.weight); > > > load = &lw; > > > @@ -697,8 +710,14 @@ static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se) > > > slice = __calc_delta(slice, se->load.weight, load); > > > } > > > > > > - if (sched_feat(BASE_SLICE)) > > > - slice = max(slice, (u64)sysctl_sched_min_granularity); > > > + if (sched_feat(BASE_SLICE)) { > > > + if (se_is_idle(init_se) && !sched_idle_cfs_rq(cfs_rq)) > > > > Like for place_entity, we should probably not dynamically switch > > between the 2 values below depending on the presence or not of non > > sched idle tasks and always use sysctl_sched_idle_min_granularity > > My reasoning here is that sched_slice is something we reasonably > expect to change as tasks enqueue/dequeue, and unlike place_entity() > it does not create fairness issues by messing with vruntime. > Additionally, it would be preferable to use the larger min granularity > on a cpu running only idle tasks. Fair enough Reviewed-by: Vincent Guittot