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[71.255.246.27]) by smtp.googlemail.com with ESMTPSA id 12sm359559qkj.136.2020.02.21.16.52.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 21 Feb 2020 16:52:19 -0800 (PST) From: Thara Gopinath To: mingo@redhat.com, peterz@infradead.org, ionela.voinescu@arm.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rui.zhang@intel.com, qperret@google.com, daniel.lezcano@linaro.org, viresh.kumar@linaro.org, rostedt@goodmis.org, will@kernel.org, catalin.marinas@arm.com, sudeep.holla@arm.com, juri.lelli@redhat.com, corbet@lwn.net Cc: linux-kernel@vger.kernel.org, amit.kachhap@gmail.com, javi.merino@kernel.org, amit.kucheria@verdurent.com Subject: [Patch v10 3/9] drivers/base/arch_topology: Add infrastructure to store and update instantaneous thermal pressure Date: Fri, 21 Feb 2020 19:52:07 -0500 Message-Id: <20200222005213.3873-4-thara.gopinath@linaro.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200222005213.3873-1-thara.gopinath@linaro.org> References: <20200222005213.3873-1-thara.gopinath@linaro.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Add architecture specific APIs to update and track thermal pressure on a 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. topology_get_thermal_pressure can be hooked into the scheduler specified arch_scale_thermal_pressure to retrieve instantaneous thermal pressure of a cpu. arch_set_thermal_pressure can be used to update the thermal pressure. Considering topology_get_thermal_pressure reads thermal_pressure and arch_set_thermal_pressure writes into thermal_pressure, one can argue for some sort of locking mechanism to avoid a stale value. But considering topology_get_thermal_pressure 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 --- v6->v7: - Changed the input argument in arch_set_thermal_pressure from capped capacity to delta capacity(thermal pressure) as per Ionela's review comments. v9->v10: - Split the patch into three thus separating out arch/arm and arch/arm64 specific code into individual patches as suggested by Amit Kucheria. drivers/base/arch_topology.c | 11 +++++++++++ include/linux/arch_topology.h | 10 ++++++++++ 2 files changed, 21 insertions(+) diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c index 6119e11a9f95..68dfa49d3b63 100644 --- a/drivers/base/arch_topology.c +++ b/drivers/base/arch_topology.c @@ -42,6 +42,17 @@ void topology_set_cpu_scale(unsigned int cpu, unsigned long capacity) per_cpu(cpu_scale, cpu) = capacity; } +DEFINE_PER_CPU(unsigned long, thermal_pressure); + +void arch_set_thermal_pressure(struct cpumask *cpus, + unsigned long th_pressure) +{ + int cpu; + + for_each_cpu(cpu, cpus) + WRITE_ONCE(per_cpu(thermal_pressure, cpu), th_pressure); +} + static ssize_t cpu_capacity_show(struct device *dev, struct device_attribute *attr, char *buf) diff --git a/include/linux/arch_topology.h b/include/linux/arch_topology.h index 3015ecbb90b1..88a115e81f27 100644 --- a/include/linux/arch_topology.h +++ b/include/linux/arch_topology.h @@ -33,6 +33,16 @@ unsigned long topology_get_freq_scale(int cpu) return per_cpu(freq_scale, cpu); } +DECLARE_PER_CPU(unsigned long, thermal_pressure); + +static inline unsigned long topology_get_thermal_pressure(int cpu) +{ + return per_cpu(thermal_pressure, cpu); +} + +void arch_set_thermal_pressure(struct cpumask *cpus, + unsigned long th_pressure); + struct cpu_topology { int thread_id; int core_id; -- 2.20.1