linux-kernel - Re: [PATCH v3 0/6] cpufreq: schedutil: fixes for flags updates

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Date:   Thu, 21 Dec 2017 13:04:05 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Patrick Bellasi <patrick.bellasi@....com>,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        Ingo Molnar <mingo@...hat.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Todd Kjos <tkjos@...roid.com>,
        Joel Fernandes <joelaf@...gle.com>
Subject: Re: [PATCH v3 0/6] cpufreq: schedutil: fixes for flags updates

On 20-12-17, 16:30, Peter Zijlstra wrote:
> 
> So I ended up with the below (on top of Juri's cpufreq-dl patches).

Nice :)

There are two things that I noticed in your tree.

Firstly, there is no need of the following patch as we shouldn't have
the problem mentioned in the commit anymore:

38e19dbe1286 cpufreq: schedutil: ignore sugov kthreads

And maybe we can apply the below patch after that (only compile
tested).

-------------------------8<-------------------------

From: Viresh Kumar <viresh.kumar@...aro.org>
Date: Thu, 21 Dec 2017 12:52:50 +0530
Subject: [PATCH] cpufreq/schedutil: Call sugov_get_util() only when required

sugov_update_shared() doesn't use the updated values of max, util_cfs
and util_dl, unless we try to find the next frequency by calling
sugov_next_freq_shared() and so there is no need to call it directly
from sugov_update_shared(). Rather postpone it until the time
sugov_next_freq_shared() is called for one of the CPUs that share the
policy.

Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
---
 kernel/sched/cpufreq_schedutil.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index ab84d2261554..f2f4df26b954 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -315,8 +315,7 @@ static unsigned int sugov_next_freq_shared(struct sugov_cpu *sg_cpu, u64 time)
 		unsigned long j_util, j_max;
 		s64 delta_ns;
 
-		if (j_sg_cpu != sg_cpu)
-			sugov_get_util(j_sg_cpu);
+		sugov_get_util(j_sg_cpu);
 
 		/*
 		 * If the CFS CPU utilization was last updated before the
@@ -354,7 +353,6 @@ static void sugov_update_shared(struct update_util_data *hook, u64 time,
 
 	raw_spin_lock(&sg_policy->update_lock);
 
-	sugov_get_util(sg_cpu);
 	sugov_set_iowait_boost(sg_cpu, time, flags);
 	sg_cpu->last_update = time;