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Thu, 22 Jan 2026 02:53:57 -0800 (PST) Received: from jlelli-thinkpadt14gen4.remote.csb ([151.29.129.40]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-48042c598b9sm48029415e9.18.2026.01.22.02.53.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 22 Jan 2026 02:53:56 -0800 (PST) Date: Thu, 22 Jan 2026 11:53:34 +0100 From: Juri Lelli To: Peter Zijlstra Cc: tglx@linutronix.de, arnd@arndb.de, anna-maria@linutronix.de, frederic@kernel.org, luto@kernel.org, mingo@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, linux-kernel@vger.kernel.org, oliver.sang@intel.com Subject: Re: [PATCH v2 1/6] sched/eevdf: Fix HRTICK duration Message-ID: References: <20260121162010.647043073@infradead.org> <20260121162507.525037175@infradead.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260121162507.525037175@infradead.org> Hello, On 21/01/26 17:20, Peter Zijlstra wrote: > The nominal duration for an EEVDF task to run is until its deadline. > At which point the deadline is moved ahead and a new task selection is > done. > > Try and predict the time 'lost' to higher scheduling classes. Since > this is an estimate, the timer can be both early or late. In case it > is early task_tick_fair() will take the !need_resched() path and > restarts the timer. > > Signed-off-by: Peter Zijlstra (Intel) > --- ... > @@ -6735,21 +6724,39 @@ static inline void sched_fair_update_sto > static void hrtick_start_fair(struct rq *rq, struct task_struct *p) > { > struct sched_entity *se = &p->se; > + unsigned long scale = 1024; > + unsigned long util = 0; > + u64 vdelta; > + u64 delta; > > WARN_ON_ONCE(task_rq(p) != rq); > > - if (rq->cfs.h_nr_queued > 1) { > - u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime; > - u64 slice = se->slice; > - s64 delta = slice - ran; > - > - if (delta < 0) { > - if (task_current_donor(rq, p)) > - resched_curr(rq); > - return; > - } > - hrtick_start(rq, delta); > + if (rq->cfs.h_nr_queued <= 1) > + return; > + > + /* > + * Compute time until virtual deadline > + */ > + vdelta = se->deadline - se->vruntime; > + if ((s64)vdelta < 0) { > + if (task_current_donor(rq, p)) > + resched_curr(rq); > + return; > + } > + delta = (se->load.weight * vdelta) / NICE_0_LOAD; Nit.. guess we don't fear overflow since vdelta should be bounded anyway. Reviewed-by: Juri Lelli Thanks, Juri