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[71.255.246.27]) by smtp.googlemail.com with ESMTPSA id j7sm6832565qkd.46.2019.11.05.10.49.49 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Tue, 05 Nov 2019 10:49:50 -0800 (PST) From: Thara Gopinath To: mingo@redhat.com, peterz@infradead.org, ionela.voinescu@arm.com, vincent.guittot@linaro.org, rui.zhang@intel.com, edubezval@gmail.com, qperret@google.com Cc: linux-kernel@vger.kernel.org, amit.kachhap@gmail.com, javi.merino@kernel.org, daniel.lezcano@linaro.org Subject: [Patch v5 2/6] sched/fair: Add infrastructure to store and update instantaneous thermal pressure Date: Tue, 5 Nov 2019 13:49:42 -0500 Message-Id: <1572979786-20361-3-git-send-email-thara.gopinath@linaro.org> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1572979786-20361-1-git-send-email-thara.gopinath@linaro.org> References: <1572979786-20361-1-git-send-email-thara.gopinath@linaro.org> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Add interface APIs to initialize, update/average, track, accumulate and decay thermal pressure per cpu basis. A per cpu variable thermal_pressure is introduced to keep track of instantaneous per cpu thermal pressure. Thermal pressure is the delta between maximum capacity and capped capacity due to a thermal event. API trigger_thermal_pressure_average is called for periodic accumulate and decay of the thermal pressure.This API passes on the instantaneous thermal pressure of a cpu to update_thermal_load_avg to do the necessary accumulate, decay and average. API update_thermal_pressure is for the system to update the thermal pressure by providing a capped maximum capacity. Considering, trigger_thermal_pressure_average reads thermal_pressure and update_thermal_pressure writes into thermal_pressure, one can argue for some sort of locking mechanism to avoid a stale value. But considering trigger_thermal_pressure_average can be called from a system critical path like scheduler tick function, a locking mechanism is not ideal. This means that it is possible the thermal_pressure value used to calculate average thermal pressure for a cpu can be stale for upto 1 tick period. Signed-off-by: Thara Gopinath --- v3->v4: - Dropped per cpu max_capacity_info struct and instead added a per delta_capacity variable to store the delta between maximum capacity and capped capacity. The delta is now calculated when thermal pressure is updated and not every tick. - Dropped populate_max_capacity_info api as only per cpu delta capacity is stored. - Renamed update_periodic_maxcap to trigger_thermal_pressure_average and update_maxcap_capacity to update_thermal_pressure. v4->v5: - As per Peter's review comments folded thermal.c into fair.c. - As per Ionela's review comments revamped update_thermal_pressure to take maximum available capacity as input instead of maximum capped frequency ration. --- include/linux/sched.h | 9 +++++++++ kernel/sched/fair.c | 37 +++++++++++++++++++++++++++++++++++++ 2 files changed, 46 insertions(+) diff --git a/include/linux/sched.h b/include/linux/sched.h index 263cf08..3c31084 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1993,6 +1993,15 @@ static inline void rseq_syscall(struct pt_regs *regs) #endif +#ifdef CONFIG_SMP +void update_thermal_pressure(int cpu, unsigned long capped_capacity); +#else +static inline void +update_thermal_pressure(int cpu, unsigned long capped_capacity) +{ +} +#endif + const struct sched_avg *sched_trace_cfs_rq_avg(struct cfs_rq *cfs_rq); char *sched_trace_cfs_rq_path(struct cfs_rq *cfs_rq, char *str, int len); int sched_trace_cfs_rq_cpu(struct cfs_rq *cfs_rq); diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 682a754..2e907cc 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -86,6 +86,12 @@ static unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL; const_debug unsigned int sysctl_sched_migration_cost = 500000UL; +/* + * Per-cpu instantaneous delta between maximum capacity + * and maximum available capacity due to thermal events. + */ +static DEFINE_PER_CPU(unsigned long, thermal_pressure); + #ifdef CONFIG_SMP /* * For asym packing, by default the lower numbered CPU has higher priority. @@ -10401,6 +10407,37 @@ static unsigned int get_rr_interval_fair(struct rq *rq, struct task_struct *task return rr_interval; } +#ifdef CONFIG_SMP +/** + * update_thermal_pressure: Update thermal pressure + * @cpu: the cpu for which thermal pressure is to be updated for + * @capped_capacity: maximum capacity of the cpu after the capping + * due to thermal event. + * + * Delta between the arch_scale_cpu_capacity and capped max capacity is + * stored in per cpu thermal_pressure variable. + */ +void update_thermal_pressure(int cpu, unsigned long capped_capacity) +{ + unsigned long delta; + + delta = arch_scale_cpu_capacity(cpu) - capped_capacity; + per_cpu(thermal_pressure, cpu) = delta; +} +#endif + +/** + * trigger_thermal_pressure_average: Trigger the thermal pressure accumulate + * and average algorithm + */ +static void trigger_thermal_pressure_average(struct rq *rq) +{ +#ifdef CONFIG_SMP + update_thermal_load_avg(rq_clock_task(rq), rq, + per_cpu(thermal_pressure, cpu_of(rq))); +#endif +} + /* * All the scheduling class methods: */ -- 2.1.4