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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 00FE8E7D0A6 for ; Thu, 21 Sep 2023 20:23:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231697AbjIUUXd (ORCPT ); Thu, 21 Sep 2023 16:23:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55954 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231654AbjIUUXH (ORCPT ); Thu, 21 Sep 2023 16:23:07 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id EE716561C5; Thu, 21 Sep 2023 10:17:39 -0700 (PDT) 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 7CA09150C; Thu, 21 Sep 2023 02:01:16 -0700 (PDT) Received: from localhost (ionvoi01-desktop.cambridge.arm.com [10.2.78.69]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id F048F3F59C; Thu, 21 Sep 2023 02:00:38 -0700 (PDT) Date: Thu, 21 Sep 2023 10:00:37 +0100 From: Ionela Voinescu To: Vincent Guittot Cc: linux@armlinux.org.uk, catalin.marinas@arm.com, will@kernel.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, sudeep.holla@arm.com, gregkh@linuxfoundation.org, rafael@kernel.org, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, bristot@redhat.com, vschneid@redhat.com, viresh.kumar@linaro.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, linux-pm@vger.kernel.org, conor.dooley@microchip.com, suagrfillet@gmail.com, ajones@ventanamicro.com, lftan@kernel.org Subject: Re: [PATCH 2/4] topology: add a new arch_scale_freq_reference Message-ID: References: <20230901130312.247719-1-vincent.guittot@linaro.org> <20230901130312.247719-3-vincent.guittot@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230901130312.247719-3-vincent.guittot@linaro.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Vincent, On Friday 01 Sep 2023 at 15:03:10 (+0200), Vincent Guittot wrote: > Create a new method to get a unique and fixed max frequency. Currently > cpuinfo.max_freq or last item of performance domain are used as the max > frequency when computing the frequency for a level of utilization but: > - cpuinfo_max_freq can change at runtime. boost is one example of > such change. > - cpuinfo.max_freq and last item of the PD can be different leading to > different results betwen cpufreq and energy model. > > We need to save the max frequency that has been used when computing the > CPUs capacity and use this fixed and coherent value to convert between > frequency and CPU's capacity. > > In fact, we already save the frequency that has been used when computing > the capacity of each CPU. We extend the precision to save khZ instead of > Mhz currently and we modify the type to be aligned with other variables > used when converting frequency to capacity and the other way. > > Signed-off-by: Vincent Guittot > --- > arch/arm/include/asm/topology.h | 1 + > arch/arm64/include/asm/topology.h | 1 + > arch/riscv/include/asm/topology.h | 1 + > drivers/base/arch_topology.c | 9 +++------ > include/linux/arch_topology.h | 7 +++++++ > 5 files changed, 13 insertions(+), 6 deletions(-) > > diff --git a/arch/arm/include/asm/topology.h b/arch/arm/include/asm/topology.h > index c7d2510e5a78..853c4f81ba4a 100644 > --- a/arch/arm/include/asm/topology.h > +++ b/arch/arm/include/asm/topology.h > @@ -13,6 +13,7 @@ > #define arch_set_freq_scale topology_set_freq_scale > #define arch_scale_freq_capacity topology_get_freq_scale > #define arch_scale_freq_invariant topology_scale_freq_invariant > +#define arch_scale_freq_ref topology_get_freq_ref The "reference" frequency or performance of a CPU has a specific meaning in the ACPI specification as a fixed frequency of a constant clock and its associated performance level, usually used for performance to frequency conversions. This is not guaranteed to be the maximum performance/frequency and it's definitely not the case for arm systems where this is tied to the system timer - 1-50Mhz. So I believe it might create some confusion to call this "reference" frequency. Any reason for not calling it arch_scale_freq_max? I know not all max frequencies are equal :) but it would still drive the point that this is intended to act as a chosen maximum for the scheduler's use, especially if there's a well place comment. > #endif > > /* Replace task scheduler's default cpu-invariant accounting */ > diff --git a/arch/arm64/include/asm/topology.h b/arch/arm64/include/asm/topology.h > index 9fab663dd2de..a323b109b9c4 100644 > --- a/arch/arm64/include/asm/topology.h > +++ b/arch/arm64/include/asm/topology.h > @@ -23,6 +23,7 @@ void update_freq_counters_refs(void); > #define arch_set_freq_scale topology_set_freq_scale > #define arch_scale_freq_capacity topology_get_freq_scale > #define arch_scale_freq_invariant topology_scale_freq_invariant > +#define arch_scale_freq_ref topology_get_freq_ref > > #ifdef CONFIG_ACPI_CPPC_LIB > #define arch_init_invariance_cppc topology_init_cpu_capacity_cppc > diff --git a/arch/riscv/include/asm/topology.h b/arch/riscv/include/asm/topology.h > index e316ab3b77f3..61183688bdd5 100644 > --- a/arch/riscv/include/asm/topology.h > +++ b/arch/riscv/include/asm/topology.h > @@ -9,6 +9,7 @@ > #define arch_set_freq_scale topology_set_freq_scale > #define arch_scale_freq_capacity topology_get_freq_scale > #define arch_scale_freq_invariant topology_scale_freq_invariant > +#define arch_scale_freq_ref topology_get_freq_ref > > /* Replace task scheduler's default cpu-invariant accounting */ > #define arch_scale_cpu_capacity topology_get_cpu_scale > diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c > index b741b5ba82bd..75fa67477a9d 100644 > --- a/drivers/base/arch_topology.c > +++ b/drivers/base/arch_topology.c > @@ -26,7 +26,7 @@ > static DEFINE_PER_CPU(struct scale_freq_data __rcu *, sft_data); > static struct cpumask scale_freq_counters_mask; > static bool scale_freq_invariant; > -static DEFINE_PER_CPU(u32, freq_factor) = 1; > +DEFINE_PER_CPU(unsigned long, freq_factor) = 1; Given its new wider use, it might be good for this to get a more relevant name as well. Previously freq_factor made sense for its role in using the dmips/mhz values to obtain CPU capacities. But if this is now returned from arch_scale_freq_ref() it would be more difficult still to easily understand what this value is supposed to reflect, when reading the function name or the per-cpu variable name alone. Thanks, Ionela. > > static bool supports_scale_freq_counters(const struct cpumask *cpus) > { > @@ -183,10 +183,7 @@ void topology_update_thermal_pressure(const struct cpumask *cpus, > > cpu = cpumask_first(cpus); > max_capacity = arch_scale_cpu_capacity(cpu); > - max_freq = per_cpu(freq_factor, cpu); > - > - /* Convert to MHz scale which is used in 'freq_factor' */ > - capped_freq /= 1000; > + max_freq = arch_scale_freq_ref(cpu); > > /* > * Handle properly the boost frequencies, which should simply clean > @@ -411,7 +408,7 @@ init_cpu_capacity_callback(struct notifier_block *nb, > cpumask_andnot(cpus_to_visit, cpus_to_visit, policy->related_cpus); > > for_each_cpu(cpu, policy->related_cpus) > - per_cpu(freq_factor, cpu) = policy->cpuinfo.max_freq / 1000; > + per_cpu(freq_factor, cpu) = policy->cpuinfo.max_freq; > > if (cpumask_empty(cpus_to_visit)) { > topology_normalize_cpu_scale(); > diff --git a/include/linux/arch_topology.h b/include/linux/arch_topology.h > index a07b510e7dc5..7a2dba9c3dc0 100644 > --- a/include/linux/arch_topology.h > +++ b/include/linux/arch_topology.h > @@ -27,6 +27,13 @@ static inline unsigned long topology_get_cpu_scale(int cpu) > > void topology_set_cpu_scale(unsigned int cpu, unsigned long capacity); > > +DECLARE_PER_CPU(unsigned long, freq_factor); > + > +static inline unsigned long topology_get_freq_ref(int cpu) > +{ > + return per_cpu(freq_factor, cpu); > +} > + > DECLARE_PER_CPU(unsigned long, arch_freq_scale); > > static inline unsigned long topology_get_freq_scale(int cpu) > -- > 2.34.1 > >