From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D2380C43603 for ; Tue, 17 Dec 2019 12:54:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A62B720663 for ; Tue, 17 Dec 2019 12:54:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728108AbfLQMyc (ORCPT ); Tue, 17 Dec 2019 07:54:32 -0500 Received: from foss.arm.com ([217.140.110.172]:36206 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727637AbfLQMyc (ORCPT ); Tue, 17 Dec 2019 07:54:32 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id B1C7931B; Tue, 17 Dec 2019 04:54:31 -0800 (PST) Received: from [192.168.0.9] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id C397F3F719; Tue, 17 Dec 2019 04:54:29 -0800 (PST) Subject: Re: [Patch v6 3/7] Add infrastructure to store and update instantaneous thermal pressure To: Thara Gopinath , mingo@redhat.com, peterz@infradead.org, ionela.voinescu@arm.com, vincent.guittot@linaro.org, rui.zhang@intel.com, qperret@google.com, daniel.lezcano@linaro.org, viresh.kumar@linaro.org Cc: linux-kernel@vger.kernel.org, amit.kachhap@gmail.com, javi.merino@kernel.org, amit.kucheria@verdurent.com References: <1576123908-12105-1-git-send-email-thara.gopinath@linaro.org> <1576123908-12105-4-git-send-email-thara.gopinath@linaro.org> From: Dietmar Eggemann Message-ID: <3ca440af-c459-3b23-64c3-0292b1106594@arm.com> Date: Tue, 17 Dec 2019 13:54:28 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2 MIME-Version: 1.0 In-Reply-To: <1576123908-12105-4-git-send-email-thara.gopinath@linaro.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/12/2019 05:11, Thara Gopinath wrote: Shouldn't the subject contain something like 'arm,arm64,drivers:' ? > 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. > capacity and capped capacity due to a thermal event. > > topology_get_thermal_pressure can be hooked into the scheduler specified > arch_scale_thermal_capacity to retrieve instantaneius thermal pressure of s/instantaneius/instantaneous > a cpu. > > arch_set_thermal_presure can be used to update the thermal pressure by s/presure/pressure > providing a capped maximum capacity. > > 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_average can be called from a system critical s/topology_get_thermal_pressure_average/topology_get_thermal_pressure ? > 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. > v5->v6: > - As per review comments moved all the infrastructure to track > and retrieve instantaneous thermal pressure out of scheduler > to topology files. > > arch/arm/include/asm/topology.h | 3 +++ > arch/arm64/include/asm/topology.h | 3 +++ > drivers/base/arch_topology.c | 13 +++++++++++++ > include/linux/arch_topology.h | 11 +++++++++++ > 4 files changed, 30 insertions(+) > > diff --git a/arch/arm/include/asm/topology.h b/arch/arm/include/asm/topology.h > index 8a0fae9..90b18c3 100644 > --- a/arch/arm/include/asm/topology.h > +++ b/arch/arm/include/asm/topology.h > @@ -16,6 +16,9 @@ > /* Enable topology flag updates */ > #define arch_update_cpu_topology topology_update_cpu_topology > > +/* Replace task scheduler's defalut thermal pressure retrieve API */ > +#define arch_scale_thermal_capacity topology_get_thermal_pressure > + > #else > > static inline void init_cpu_topology(void) { } > diff --git a/arch/arm64/include/asm/topology.h b/arch/arm64/include/asm/topology.h > index a4d945d..ccb277b 100644 > --- a/arch/arm64/include/asm/topology.h > +++ b/arch/arm64/include/asm/topology.h > @@ -25,6 +25,9 @@ int pcibus_to_node(struct pci_bus *bus); > /* Enable topology flag updates */ > #define arch_update_cpu_topology topology_update_cpu_topology > > +/* Replace task scheduler's defalut thermal pressure retrieve API */ > +#define arch_scale_thermal_capacity topology_get_thermal_pressure > + > #include > > #endif /* _ASM_ARM_TOPOLOGY_H */ > diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c > index 1eb81f11..3a91379 100644 > --- a/drivers/base/arch_topology.c > +++ b/drivers/base/arch_topology.c > @@ -42,6 +42,19 @@ 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 capped_capacity) > +{ > + int cpu; > + unsigned long delta = arch_scale_cpu_capacity(cpumask_first(cpus)) - > + capped_capacity; unsigned long delta; int cpu; delta = arch_scale_cpu_capacity(cpumask_first(cpus)) - capped_capacity; Easier to read plus order local variable declarations from longest to shortest line. https://lore.kernel.org/r/20181107171149.165693799@linutronix.de > + > + for_each_cpu(cpu, cpus) > + WRITE_ONCE(per_cpu(thermal_pressure, cpu), delta); > +} > + > 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 3015ecb..7a04364 100644 > --- a/include/linux/arch_topology.h > +++ b/include/linux/arch_topology.h > @@ -33,6 +33,17 @@ 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) Save one line: 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 capped_capacity); > + > struct cpu_topology { > int thread_id; > int core_id; >