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dkim=pass header.d=linaro.org header.s=google header.b=uz4sGI+1; spf=pass (imf08.hostedemail.com: domain of vincent.guittot@linaro.org designates 209.85.208.180 as permitted sender) smtp.mailfrom=vincent.guittot@linaro.org; dmarc=pass (policy=none) header.from=linaro.org X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: C0C971600B4 X-Stat-Signature: b4njkkik717b5gcqgfp47n48iqn9kazy X-Rspam-User: X-HE-Tag: 1663335426-321968 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hi Hillf, On Fri, 16 Sept 2022 at 14:03, Hillf Danton wrote: > > Hello Vincent > > On 16 Sep 2022 10:03:02 +0200 Vincent Guittot wrote: > > > > @@ -4606,6 +4608,7 @@ check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr) > > > > se = __pick_first_entity(cfs_rq); > > delta = curr->vruntime - se->vruntime; > > + delta -= wakeup_latency_gran(curr, se); > > > > if (delta < 0) > > return; > > What is derived from the latency nice you added is the runtime granulaity > which has a role in preempting the current task. > > Given the same defination of latency nice as the nice, the runtime granularity > can be computed without introducing the latency nice. > > Only for thoughts now. > > Hillf > > +++ b/kernel/sched/fair.c > @@ -4569,7 +4569,7 @@ dequeue_entity(struct cfs_rq *cfs_rq, st > static void > check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr) > { > - unsigned long ideal_runtime, delta_exec; > + unsigned long ideal_runtime, delta_exec, granu; > struct sched_entity *se; > s64 delta; > > @@ -4594,6 +4594,14 @@ check_preempt_tick(struct cfs_rq *cfs_rq > return; > > se = __pick_first_entity(cfs_rq); > + > + granu = sysctl_sched_min_granularity + > + (ideal_runtime - sysctl_sched_min_granularity) * > + (se->latency_nice + 20) / LATENCY_NICE_WIDTH; There is no latency_nice field in se but a latency_offset instead Also at this step, we are sure that curr has run at least sysctl_sched_min_granularity and we want now to compare curr vruntime with first se's one. We take the latency offset into account to make sure we will not preempt curr too early > + > + if (delta_exec < granu) > + return; > + > delta = curr->vruntime - se->vruntime; > > if (delta < 0)