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 4B3701DD0C7 for ; Thu, 14 Aug 2025 08:46:25 +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=1755161187; cv=none; b=BjC6V3MG7iYR0SMEKccZQ6jITy2ad+JlTYMTxVzjTo9WzDtbNQvYC+4YLAjoGVhSjXcEv+eggetmzahRiCkanlv1iFQV040NsAl3NhuEBHyjJQB8uy9gtLHkJ/iNDXOQplJmdRUm2c+6xRPgKhDE4SNVXeMZoyaadHRL8qOFuKE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755161187; c=relaxed/simple; bh=REw+v6U5HjfZ8GlRbNV5DektWf+6ind2kNIhpdPnbF0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=bYOWuqyzwDlq6OcnIxgCM3701sahOztbuAHMfKxhKndKGkfctLTExb33Id3X6ZjbsSXFQt4gkny5Iq4j/425d/8J+H0LvwFPG86He4DXUM+yrlsAo9WAx3ZYQP0nHsh46uf6MY1LpQlPfCyOnXCjHuezoK3zp6mw0KlRjFd/bO8= 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 C8493168F; Thu, 14 Aug 2025 01:46:09 -0700 (PDT) Received: from [10.13.87.1] (usa-sjc-mx-foss1.foss.arm.com [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1D2253F738; Thu, 14 Aug 2025 01:46:13 -0700 (PDT) Message-ID: Date: Thu, 14 Aug 2025 09:46:08 +0100 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: [RFC PATCH] sched/feec: Simplify the traversal of pd'cpus To: Xuewen Yan , mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org Cc: rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, vdonnefort@google.com, ke.wang@unisoc.com, xuewen.yan94@gmail.com, linux-kernel@vger.kernel.org References: <20250812093339.8895-1-xuewen.yan@unisoc.com> Content-Language: en-GB From: Dietmar Eggemann In-Reply-To: <20250812093339.8895-1-xuewen.yan@unisoc.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 12.08.25 10:33, Xuewen Yan wrote: > Now we use for_each_cpu() to traversal all pd's cpus, > it is in order to compute the pd_cap. This approach may > result in some unnecessary judgments. > We can simply calculate pd_cap as follows: > > pd_cap = cpu_actual_cap * cpumask_weight(pd_cpus); > > Then we can AND pd'scpus, sd's cpus and task's cpus_ptr > before traversing, which can save some unnecessary judgment. > > Signed-off-by: Xuewen Yan > --- > kernel/sched/fair.c | 14 ++++---------- > 1 file changed, 4 insertions(+), 10 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index b173a059315c..e47fe94d6889 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -8330,18 +8330,12 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu) Just a thought ... for (; pd; pd = pd->next) cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr); <-- (1) cpumask_and(cpus, perf_domain_span(pd), cpu_online_mask); if (cpumask_empty(cpus)) continue; <-- (2) Can you not mask cpus already early in the pd loop (1) and then profit from (2) in these rare cases? IIRC, the sd only plays a role here in exclusive cpusets scenarios which I don't thing anybody deploys with EAS? > cpu_actual_cap = get_actual_cpu_capacity(cpu); > > eenv.cpu_cap = cpu_actual_cap; > - eenv.pd_cap = 0; > + eenv.pd_cap = cpu_actual_cap * cpumask_weight(cpus); > > - for_each_cpu(cpu, cpus) { > - struct rq *rq = cpu_rq(cpu); > - > - eenv.pd_cap += cpu_actual_cap; > - > - if (!cpumask_test_cpu(cpu, sched_domain_span(sd))) > - continue; > + cpumask_and(cpus, cpus, sched_domain_span(sd)); > > - if (!cpumask_test_cpu(cpu, p->cpus_ptr)) > - continue; > + for_each_cpu_and(cpu, cpus, p->cpus_ptr) { > + struct rq *rq = cpu_rq(cpu); > > util = cpu_util(cpu, p, cpu, 0); > cpu_cap = capacity_of(cpu);