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Thu, 22 Oct 2026 07:27:41 -0700 (PDT) Received: from scheduler.schedules ([85.100.66.184]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48e2581f15esm13604454f8f.20.2026.10.22.07.27.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 22 Oct 2026 07:27:41 -0700 (PDT) Date: Thu, 22 Oct 2026 17:27:38 +0300 From: Kayra Cizmeci To: Hui Su Cc: Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , K Prateek Nayak , linux-kernel@vger.kernel.org Subject: Re: [PATCH] sched/pelt: Fix truncation of the PELT period count Message-ID: References: <20261022034930.225042-1-sh_def@163.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20261022034930.225042-1-sh_def@163.com> On Thu, Oct 22, 2026 at 12:49:30PM +0900, Hui Su wrote: > accumulate_sum() computes the number of elapsed PELT periods in a > u64 but returns u32. When the count is a multiple of 2^32, it is > truncated to zero even though the PELT sums have been updated. > > The caller interprets zero as no period boundary crossed and skips > recomputing the averages, leaving *_avg stale relative to *_sum. > > Return only whether any period elapsed, which is all the caller > needs. > > Signed-off-by: Hui Su > --- > kernel/sched/pelt.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/sched/pelt.c b/kernel/sched/pelt.c > index 779eb58a4261..519bc9c40043 100644 > --- a/kernel/sched/pelt.c > +++ b/kernel/sched/pelt.c > @@ -146,7 +146,7 @@ accumulate_sum(u64 delta, struct sched_avg *sa, > if (running) > sa->util_sum += contrib << SCHED_CAPACITY_SHIFT; > > - return periods; > + return !!periods; > } I think making this return value u64 is cleaner (As Prateek says). Both works for me tho. Reviewed-by: Kayra Cizmeci > > /* > -- > 2.55.0 >