From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 65E0A1DEFF5; Tue, 28 Jan 2025 08:52:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=13.77.154.182 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738054367; cv=none; b=HRjHVxy8l+qHVj9ph8E8QZ5XftLsqg0SKDW0OQIQIdeyfv3/taf68wAK29LFlJilE+E0r/Nz2YSekAhnzF3r66025X/yezYgDFMKmj8SiRRQWzFfYZOTpeMmk4X8anXnkApW4MWThepPpM+6goC2dBjrViEbB5GSL2aLQElpeVA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738054367; c=relaxed/simple; bh=UTVgwIujyrxr3/DxN8Lw9xvbJVx2Nj69M2saIqez5fY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=FYjTGLy9qBJ8YFXrOiOB7eqnb6p1jXVK/+rOXoOzO169bLMoUjOyTLSqFTlNrZeUKLdBiR2vBJgDO1J3HcZB3Rrgk8EbBpjkk8L7IECmrPvvBW4WMdP74vm1WqqhQCmZhATCai1SqZa+iaMXFtIfbJtR3hLe6pTZw3r7bfE1uW4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.microsoft.com; spf=pass smtp.mailfrom=linux.microsoft.com; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b=iGNZX0/1; arc=none smtp.client-ip=13.77.154.182 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.microsoft.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.microsoft.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b="iGNZX0/1" Received: from [10.156.205.88] (unknown [167.220.238.88]) by linux.microsoft.com (Postfix) with ESMTPSA id 4F1AD210C30E; Tue, 28 Jan 2025 00:52:42 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 4F1AD210C30E DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1738054365; bh=hJx8UmUlmyEY04VtwlsR6MpP14zQaxU4awBvo3kjM1o=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=iGNZX0/1Bsm12KujdQyHZ2SDB7PQI9enaCjDoD5EyP+aFjY5pC0lue20VJYqQP01T f4aSC2Ife9OLVi7SdAKymm0BQ1qoX6NNnsO0kpbZWR+i9ss3MaelR74j2hz1g2sjXs R/Em8s21FAYPH6yMITKpHBVFxcOULdJSsFOQAI6g= Message-ID: <2378348f-1a0f-4aa0-81b1-d62a4ee9a5b2@linux.microsoft.com> Date: Tue, 28 Jan 2025 14:22:40 +0530 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v9 4/5] arm64: Provide an AMU-based version of arch_freq_get_on_cpu To: Beata Michalska 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 References: <20250121084435.2839280-1-beata.michalska@arm.com> <20250121084435.2839280-5-beata.michalska@arm.com> Content-Language: en-US From: Prasanna Kumar T S M In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 28-01-2025 13:46, Beata Michalska wrote: > 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. Feel free to pick whichever option you feel is best. Don't spin a new version just to change this. I missed adding this in my previous email. Looks good to me. Reviewed-by: Prasanna Kumar T S M . > > --- > 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;