From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 4445D1DEFF1; Tue, 28 Jan 2025 08:17:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738052258; cv=none; b=WGhlu2k0PPpepjvifhWs5wJa/8InE1oA8WRWr1NGbynecKtXIqp5R7lCqm0XH+C5+Jpt+rB+CtlM7l84Lzi8JP5oskWCNnoBOzOLsAiFoCRUupKYFLuW1riTthKBtY01AIt9O6+tCVyi8nIYcgg9Zbg9ng9EggBpJPadJ6NUuSM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738052258; c=relaxed/simple; bh=ZefN+19FZJsYqwINpUePiyb3x6/oAThHnHnVCY+7+ko=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=av85L2vZlIje5AS/+fFPW22IfIoVE1Z5sUXezR5YK27LGD2SD8fMzNRVZoe3Ih05XS2qrf75FctJzeP7dyvaYZ3CJvP0dP/hOeNI/bTSKqCpRFGdAiPSW1afNy6qBD1JhNdfLRXaZ66+F2y95ll4WtPEQqXMWZATnAPsLfzM1Ao= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com 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 13257497; Tue, 28 Jan 2025 00:18:02 -0800 (PST) Received: from arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B20BB3F694; Tue, 28 Jan 2025 00:17:31 -0800 (PST) Date: Tue, 28 Jan 2025 09:16:52 +0100 From: Beata Michalska To: Prasanna Kumar T S M Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-pm@vger.kernel.org, ionela.voinescu@arm.com, sudeep.holla@arm.com, will@kernel.org, catalin.marinas@arm.com, rafael@kernel.org, viresh.kumar@linaro.org, sumitg@nvidia.com, yang@os.amperecomputing.com, vanshikonda@os.amperecomputing.com, lihuisong@huawei.com, zhanjie9@hisilicon.com Subject: Re: [PATCH v9 4/5] arm64: Provide an AMU-based version of arch_freq_get_on_cpu Message-ID: References: <20250121084435.2839280-1-beata.michalska@arm.com> <20250121084435.2839280-5-beata.michalska@arm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri, Jan 24, 2025 at 10:13:30AM +0530, Prasanna Kumar T S M wrote: > > On 21-01-2025 14:14, Beata Michalska wrote: > > With the Frequency Invariance Engine (FIE) being already wired up with > > sched tick and making use of relevant (core counter and constant > > counter) AMU counters, getting the average frequency for a given CPU, > > can be achieved by utilizing the frequency scale factor which reflects > > an average CPU frequency for the last tick period length. > > > > The solution is partially based on APERF/MPERF implementation of > > arch_freq_get_on_cpu. > > > > Suggested-by: Ionela Voinescu > > Signed-off-by: Beata Michalska > > --- > > arch/arm64/kernel/topology.c | 109 +++++++++++++++++++++++++++++++---- > > 1 file changed, 99 insertions(+), 10 deletions(-) > > > > diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c > > index cb180684d10d..5f5738b174c7 100644 > > --- a/arch/arm64/kernel/topology.c > > +++ b/arch/arm64/kernel/topology.c > > @@ -17,6 +17,7 @@ > > #include > > #include > > #include > > +#include > > #include > > #include > > @@ -88,18 +89,28 @@ int __init parse_acpi_topology(void) > > * initialized. > > */ > > static DEFINE_PER_CPU_READ_MOSTLY(unsigned long, arch_max_freq_scale) = 1UL << (2 * SCHED_CAPACITY_SHIFT); > > -static DEFINE_PER_CPU(u64, arch_const_cycles_prev); > > -static DEFINE_PER_CPU(u64, arch_core_cycles_prev); > > static cpumask_var_t amu_fie_cpus; > > +struct amu_cntr_sample { > > + u64 arch_const_cycles_prev; > > + u64 arch_core_cycles_prev; > > + unsigned long last_scale_update; > > +}; > > + > > +static DEFINE_PER_CPU_SHARED_ALIGNED(struct amu_cntr_sample, cpu_amu_samples); > > + > > void update_freq_counters_refs(void) > > { > > - this_cpu_write(arch_core_cycles_prev, read_corecnt()); > > - this_cpu_write(arch_const_cycles_prev, read_constcnt()); > > + struct amu_cntr_sample *amu_sample = this_cpu_ptr(&cpu_amu_samples); > > + > > + amu_sample->arch_core_cycles_prev = read_corecnt(); > > + amu_sample->arch_const_cycles_prev = read_constcnt(); > > } > > static inline bool freq_counters_valid(int cpu) > > { > > + struct amu_cntr_sample *amu_sample = per_cpu_ptr(&cpu_amu_samples, cpu); > > + > > if ((cpu >= nr_cpu_ids) || !cpumask_test_cpu(cpu, cpu_present_mask)) > > return false; > > @@ -108,8 +119,8 @@ static inline bool freq_counters_valid(int cpu) > > return false; > > } > > - if (unlikely(!per_cpu(arch_const_cycles_prev, cpu) || > > - !per_cpu(arch_core_cycles_prev, cpu))) { > > + if (unlikely(!amu_sample->arch_const_cycles_prev || > > + !amu_sample->arch_core_cycles_prev)) { > > pr_debug("CPU%d: cycle counters are not enabled.\n", cpu); > > return false; > > } > > @@ -152,17 +163,22 @@ void freq_inv_set_max_ratio(int cpu, u64 max_rate) > > static void amu_scale_freq_tick(void) > > { > > + struct amu_cntr_sample *amu_sample = this_cpu_ptr(&cpu_amu_samples); > > u64 prev_core_cnt, prev_const_cnt; > > u64 core_cnt, const_cnt, scale; > > - prev_const_cnt = this_cpu_read(arch_const_cycles_prev); > > - prev_core_cnt = this_cpu_read(arch_core_cycles_prev); > > + prev_const_cnt = amu_sample->arch_const_cycles_prev; > > + prev_core_cnt = amu_sample->arch_core_cycles_prev; > > update_freq_counters_refs(); > > - const_cnt = this_cpu_read(arch_const_cycles_prev); > > - core_cnt = this_cpu_read(arch_core_cycles_prev); > > + const_cnt = amu_sample->arch_const_cycles_prev; > > + core_cnt = amu_sample->arch_core_cycles_prev; > > + /* > > + * This should not happen unless the AMUs have been reset and the > > + * counter values have not been restored - unlikely > > + */ > > if (unlikely(core_cnt <= prev_core_cnt || > > const_cnt <= prev_const_cnt)) > > return; > > @@ -182,6 +198,8 @@ static void amu_scale_freq_tick(void) > > scale = min_t(unsigned long, scale, SCHED_CAPACITY_SCALE); > > this_cpu_write(arch_freq_scale, (unsigned long)scale); > > + > > + amu_sample->last_scale_update = jiffies; > > } > > static struct scale_freq_data amu_sfd = { > > @@ -189,6 +207,77 @@ static struct scale_freq_data amu_sfd = { > > .set_freq_scale = amu_scale_freq_tick, > > }; > > +static __always_inline bool amu_fie_cpu_supported(unsigned int cpu) > > +{ > > + return cpumask_available(amu_fie_cpus) && > > + cpumask_test_cpu(cpu, amu_fie_cpus); > > +} > > + > > +#define AMU_SAMPLE_EXP_MS 20 > > + > > +int arch_freq_get_on_cpu(int cpu) > > +{ > > + struct amu_cntr_sample *amu_sample; > > + unsigned int start_cpu = cpu; > > + unsigned long last_update; > > + unsigned int freq = 0; > > + u64 scale; > > + > > + if (!amu_fie_cpu_supported(cpu) || !arch_scale_freq_ref(cpu)) > > + return -EOPNOTSUPP; > > + > > +retry: > > + amu_sample = per_cpu_ptr(&cpu_amu_samples, cpu); > > + > > + last_update = amu_sample->last_scale_update; > > + > > + /* > > + * For those CPUs that are in full dynticks mode, or those that have > > + * not seen tick for a while, try an alternative source for the counters > > + * (and thus freq scale), if available, for given policy: this boils > > + * down to identifying an active cpu within the same freq domain, if any. > > + */ > > + if (!housekeeping_cpu(cpu, HK_TYPE_TICK) || > > + time_is_before_jiffies(last_update + msecs_to_jiffies(AMU_SAMPLE_EXP_MS))) { > > + struct cpufreq_policy *policy = cpufreq_cpu_get(cpu); > > + int ref_cpu = cpu; > > + > > + if (!policy) > > + return -EINVAL; > > + > > + if (!cpumask_intersects(policy->related_cpus, > > + housekeeping_cpumask(HK_TYPE_TICK))) { > > + cpufreq_cpu_put(policy); > > + return -EOPNOTSUPP; > > + } > > + > > + > > + do { > > + ref_cpu = cpumask_next_wrap(ref_cpu, policy->cpus, > > + start_cpu, false); > > + > > + } while (ref_cpu < nr_cpu_ids && idle_cpu(ref_cpu)); > > + > > + cpufreq_cpu_put(policy); > > + > > + if (ref_cpu >= nr_cpu_ids) > > + /* No alternative to pull info from */ > > + return -EAGAIN; > > + > > + cpu = ref_cpu; > > + goto retry; > > If you are going to spin a new revision, can you use while loop instead of > using goto for looping? This will help improve the readability. Can do, I guess, if you believe it will be more readable that way - me myself slightly hesitating about that. --- BR Beata > > > + } > > + /* > > + * Reversed computation to the one used to determine > > + * the arch_freq_scale value > > + * (see amu_scale_freq_tick for details) > > + */ > > + scale = arch_scale_freq_capacity(cpu); > > + freq = scale * arch_scale_freq_ref(cpu); > > + freq >>= SCHED_CAPACITY_SHIFT; > > + return freq; > > +} > > + > > static void amu_fie_setup(const struct cpumask *cpus) > > { > > int cpu;