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[71.255.246.27]) by smtp.gmail.com with ESMTPSA id b35sm1567396qtc.9.2020.02.13.06.11.38 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 13 Feb 2020 06:11:39 -0800 (PST) Subject: Re: [Patch v9 1/8] sched/pelt: Add support to track thermal pressure To: Amit Kucheria References: <1580250967-4386-1-git-send-email-thara.gopinath@linaro.org> <1580250967-4386-2-git-send-email-thara.gopinath@linaro.org> Cc: Ingo Molnar , Peter Zijlstra , ionela.voinescu@arm.com, Vincent Guittot , Dietmar Eggemann , Zhang Rui , qperret@google.com, Daniel Lezcano , Viresh Kumar , Steven Rostedt , Will Deacon , Catalin Marinas , Sudeep Holla , Juri Lelli , corbet@lwn.net, LKML , Amit Daniel Kachhap , Javi Merino From: Thara Gopinath Message-ID: <5E455919.5090506@linaro.org> Date: Thu, 13 Feb 2020 09:11:37 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/13/2020 07:29 AM, Amit Kucheria wrote: > On Wed, Jan 29, 2020 at 4:06 AM Thara Gopinath > wrote: >> >> Extrapolating on the existing framework to track rt/dl utilization using >> pelt signals, add a similar mechanism to track thermal pressure. The >> difference here from rt/dl utilization tracking is that, instead of >> tracking time spent by a cpu running a rt/dl task through util_avg, the >> average thermal pressure is tracked through load_avg. This is because >> thermal pressure signal is weighted "delta" capacity and is not >> binary(util_avg is binary). "delta capacity" here means delta between the >> actual capacity of a cpu and the decreased capacity a cpu due to a thermal >> event. >> >> In order to track average thermal pressure, a new sched_avg variable >> avg_thermal is introduced. Function update_thermal_load_avg can be called >> to do the periodic bookkeeping (accumulate, decay and average) of the >> thermal pressure. >> >> Signed-off-by: Thara Gopinath >> Reviewed-by: Vincent Guittot >> --- >> >> v6->v7: >> - Added CONFIG_HAVE_SCHED_THERMAL_PRESSURE to stub out >> update_thermal_load_avg in unsupported architectures as per >> review comments from Peter, Dietmar and Quentin. >> - Updated comment for update_thermal_load_avg as per review >> comments from Peter and Dietmar. >> v7->v8: >> - Fixed typo in defining update_thermal_load_avg which was >> causing build errors (reported by kbuild test report) >> v8->v9: >> - Defined thermal_load_avg to read rq->avg_thermal.load_avg and >> avoid cacheline miss in unsupported cases as per Peter's >> suggestion. >> >> include/trace/events/sched.h | 4 ++++ >> init/Kconfig | 4 ++++ >> kernel/sched/pelt.c | 31 +++++++++++++++++++++++++++++++ >> kernel/sched/pelt.h | 31 +++++++++++++++++++++++++++++++ >> kernel/sched/sched.h | 3 +++ >> 5 files changed, 73 insertions(+) >> >> diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h >> index 420e80e..a8fb667 100644 >> --- a/include/trace/events/sched.h >> +++ b/include/trace/events/sched.h >> @@ -613,6 +613,10 @@ DECLARE_TRACE(pelt_dl_tp, >> TP_PROTO(struct rq *rq), >> TP_ARGS(rq)); >> >> +DECLARE_TRACE(pelt_thermal_tp, >> + TP_PROTO(struct rq *rq), >> + TP_ARGS(rq)); >> + >> DECLARE_TRACE(pelt_irq_tp, >> TP_PROTO(struct rq *rq), >> TP_ARGS(rq)); >> diff --git a/init/Kconfig b/init/Kconfig >> index bd9f1fd..055c3bf 100644 >> --- a/init/Kconfig >> +++ b/init/Kconfig >> @@ -463,6 +463,10 @@ config HAVE_SCHED_AVG_IRQ >> depends on IRQ_TIME_ACCOUNTING || PARAVIRT_TIME_ACCOUNTING >> depends on SMP >> >> +config HAVE_SCHED_THERMAL_PRESSURE >> + bool "Enable periodic averaging of thermal pressure" >> + depends on SMP >> + >> config BSD_PROCESS_ACCT >> bool "BSD Process Accounting" >> depends on MULTIUSER >> diff --git a/kernel/sched/pelt.c b/kernel/sched/pelt.c >> index bd006b7..5d1fbf0 100644 >> --- a/kernel/sched/pelt.c >> +++ b/kernel/sched/pelt.c >> @@ -367,6 +367,37 @@ int update_dl_rq_load_avg(u64 now, struct rq *rq, int running) >> return 0; >> } >> >> +#ifdef CONFIG_HAVE_SCHED_THERMAL_PRESSURE >> +/* >> + * thermal: >> + * >> + * load_sum = \Sum se->avg.load_sum but se->avg.load_sum is not tracked >> + * >> + * util_avg and runnable_load_avg are not supported and meaningless. >> + * >> + * Unlike rt/dl utilization tracking that track time spent by a cpu >> + * running a rt/dl task through util_avg, the average thermal pressure is >> + * tracked through load_avg. This is because thermal pressure signal is >> + * weighted "delta" capacity and is not binary(util_avg is binary). "delta > > May I suggest a slight rewording here and in the commit description, > > This is because the thermal pressure signal is weighted "delta" > capacity unlike util_avg which is binary. Sure! Will fix it. > > It would also help, if you expanded on what you mean by binary in the > commit description and how the delta capacity is weighted. I don't understand this. Binary means 0 or 1. delta capacity is time weighted, i will update this. > >> + * capacity" here means delta between the actual capacity of a cpu and the >> + * decreased capacity a cpu due to a thermal event. > > Use consistent wording throughout the series - either capped or > decreased capacity. > >> + */ > > This could be shortened to: > > Delta capacity of cpu = Actual capacity - Capped capacity due to thermal event Will fix this. > >> +int update_thermal_load_avg(u64 now, struct rq *rq, u64 capacity) >> +{ >> + if (___update_load_sum(now, &rq->avg_thermal, >> + capacity, >> + capacity, >> + capacity)) { >> + ___update_load_avg(&rq->avg_thermal, 1, 1); >> + trace_pelt_thermal_tp(rq); >> + return 1; >> + } >> + >> + return 0; >> +} >> +#endif >> + >> #ifdef CONFIG_HAVE_SCHED_AVG_IRQ >> /* >> * irq: >> diff --git a/kernel/sched/pelt.h b/kernel/sched/pelt.h >> index afff644..916979a 100644 >> --- a/kernel/sched/pelt.h >> +++ b/kernel/sched/pelt.h >> @@ -7,6 +7,26 @@ int __update_load_avg_cfs_rq(u64 now, struct cfs_rq *cfs_rq); >> int update_rt_rq_load_avg(u64 now, struct rq *rq, int running); >> int update_dl_rq_load_avg(u64 now, struct rq *rq, int running); >> >> +#ifdef CONFIG_HAVE_SCHED_THERMAL_PRESSURE >> +int update_thermal_load_avg(u64 now, struct rq *rq, u64 capacity); >> + >> +static inline u64 thermal_load_avg(struct rq *rq) >> +{ >> + return READ_ONCE(rq->avg_thermal.load_avg); >> +} >> +#else >> +static inline int >> +update_thermal_load_avg(u64 now, struct rq *rq, u64 capacity) >> +{ >> + return 0; >> +} >> + >> +static inline u64 thermal_load_avg(struct rq *rq) >> +{ >> + return 0; >> +} >> +#endif >> + >> #ifdef CONFIG_HAVE_SCHED_AVG_IRQ >> int update_irq_load_avg(struct rq *rq, u64 running); >> #else >> @@ -159,6 +179,17 @@ update_dl_rq_load_avg(u64 now, struct rq *rq, int running) >> } >> >> static inline int >> +update_thermal_load_avg(u64 now, struct rq *rq, u64 capacity) >> +{ >> + return 0; >> +} >> + >> +static inline u64 thermal_load_avg(struct rq *rq) >> +{ >> + return 0; >> +} >> + >> +static inline int >> update_irq_load_avg(struct rq *rq, u64 running) >> { >> return 0; >> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h >> index 1a88dc8..1f256cb 100644 >> --- a/kernel/sched/sched.h >> +++ b/kernel/sched/sched.h >> @@ -944,6 +944,9 @@ struct rq { >> #ifdef CONFIG_HAVE_SCHED_AVG_IRQ >> struct sched_avg avg_irq; >> #endif >> +#ifdef CONFIG_HAVE_SCHED_THERMAL_PRESSURE >> + struct sched_avg avg_thermal; >> +#endif >> u64 idle_stamp; >> u64 avg_idle; >> >> -- >> 2.1.4 >> -- Warm Regards Thara