linux-kernel - [PATCH] sched: fix incorrect PELT values on SMT

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Message-Id: <1471571741-19504-1-git-send-email-smuckle@linaro.org>
Date:   Thu, 18 Aug 2016 18:55:41 -0700
From:   Steve Muckle <steve.muckle@...aro.org>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Juri Lelli <Juri.Lelli@....com>,
        Patrick Bellasi <patrick.bellasi@....com>,
        Steve Muckle <smuckle@...aro.org>
Subject: [PATCH] sched: fix incorrect PELT values on SMT

PELT scales its util_sum and util_avg values via
arch_scale_cpu_capacity(). If that function is passed the CPU's sched
domain then it will reduce the scaling capacity if SD_SHARE_CPUCAPACITY
is set. PELT does not pass in the sd however. The other caller of
arch_scale_cpu_capacity, update_cpu_capacity(), does. This means
util_sum and util_avg scale beyond the CPU capacity on SMT.

On an Intel i7-3630QM for example rq->cpu_capacity_orig is 589 but
util_avg scales up to 1024.

Fix this by passing in the sd in __update_load_avg() as well.

Signed-off-by: Steve Muckle <smuckle@...aro.org>
---
 kernel/sched/fair.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 61d485421bed..95d34b337152 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2731,7 +2731,7 @@ __update_load_avg(u64 now, int cpu, struct sched_avg *sa,
 	sa->last_update_time = now;
 
 	scale_freq = arch_scale_freq_capacity(NULL, cpu);
-	scale_cpu = arch_scale_cpu_capacity(NULL, cpu);
+	scale_cpu = arch_scale_cpu_capacity(cpu_rq(cpu)->sd, cpu);
 
 	/* delta_w is the amount already accumulated against our next period */
 	delta_w = sa->period_contrib;
-- 
2.7.3