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[81.157.90.255]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-42127069305sm95128755e9.22.2024.06.01.15.40.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 01 Jun 2024 15:40:18 -0700 (PDT) Date: Sat, 1 Jun 2024 23:40:17 +0100 From: Qais Yousef To: "Rafael J. Wysocki" , Viresh Kumar , Ingo Molnar , Peter Zijlstra , Vincent Guittot , Juri Lelli Cc: Steven Rostedt , Dietmar Eggemann , Ben Segall , Mel Gorman , Daniel Bristot de Oliveira , Valentin Schneider , Christian Loehle , Hongyan Xia , John Stultz , linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v5] sched: Consolidate cpufreq updates Message-ID: <20240601224017.qku2mhbaz4vsh3a3@airbuntu> References: <20240530104653.1234004-1-qyousef@layalina.io> Precedence: bulk X-Mailing-List: linux-pm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20240530104653.1234004-1-qyousef@layalina.io> On 05/30/24 11:46, Qais Yousef wrote: > +static __always_inline void > +__update_cpufreq_ctx_switch(struct rq *rq, struct task_struct *prev) > +{ I found a problem here. We should check if prev was sugov task. I hit a corner case where we were constantly switching between RT task and sugov. if (prev && prev->dl.flags & SCHED_FLAG_SUGOV) { /* Sugov just did an update, don't be too aggressive */ return; } > +#ifdef CONFIG_CPU_FREQ > + /* > + * RT and DL should always send a freq update. But we can do some > + * simple checks to avoid it when we know it's not necessary. > + * > + * iowait_boost will always trigger a freq update too. > + * > + * Fair tasks will only trigger an update if the root cfs_rq has > + * decayed. > + * > + * Everything else should do nothing. > + */ > + switch (current->policy) { > + case SCHED_NORMAL: > + case SCHED_BATCH: > + if (unlikely(current->in_iowait)) { > + cpufreq_update_util(rq, SCHED_CPUFREQ_IOWAIT | SCHED_CPUFREQ_FORCE_UPDATE); > + return; > + } > + > +#ifdef CONFIG_SMP > + if (unlikely(rq->cfs.decayed)) { > + rq->cfs.decayed = false; > + cpufreq_update_util(rq, 0); > + return; > + } > +#endif > + return; > + case SCHED_FIFO: > + case SCHED_RR: > + if (prev && rt_policy(prev->policy)) { > +#ifdef CONFIG_UCLAMP_TASK > + unsigned long curr_uclamp_min = uclamp_eff_value(current, UCLAMP_MIN); > + unsigned long prev_uclamp_min = uclamp_eff_value(prev, UCLAMP_MIN); > + > + if (curr_uclamp_min == prev_uclamp_min) > +#endif > + return; > + } > +#ifdef CONFIG_SMP > + /* Stopper task masquerades as RT */ > + if (unlikely(current->sched_class == &stop_sched_class)) > + return; > +#endif > + cpufreq_update_util(rq, SCHED_CPUFREQ_FORCE_UPDATE); > + return; > + case SCHED_DEADLINE: > + if (current->dl.flags & SCHED_FLAG_SUGOV) { > + /* Ignore sugov kthreads, they're responding to our requests */ > + return; > + } > + cpufreq_update_util(rq, SCHED_CPUFREQ_FORCE_UPDATE); > + return; > + default: > + return; > + } > +#endif > +}