linux-kernel - [PATCH 2/2] sched/uclamp: Fix iowait boost escaping uclamp restriction

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Message-Id: <20211216225320.2957053-3-qais.yousef@arm.com>
Date:   Thu, 16 Dec 2021 22:53:20 +0000
From:   Qais Yousef <qais.yousef@....com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>
Cc:     Dietmar Eggemann <dietmar.eggemann@....com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Beata Michalska <Beata.Michalska@....com>,
        Ionela Voinescu <ionela.voinescu@....com>,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Qais Yousef <qais.yousef@....com>
Subject: [PATCH 2/2] sched/uclamp: Fix iowait boost escaping uclamp restriction

iowait_boost signal is applied independently of util and doesn't take
into account uclamp settings of the rq. An io heavy task that is capped
by uclamp_max could still request higher frequency because
sugov_iowait_apply() doesn't clamp the boost via uclamp_rq_util_with()
like effective_cpu_util() does.

Make sure that iowait_boost honours uclamp requests by calling
uclamp_rq_util_with() when applying the boost.

Fixes: 982d9cdc22c9 ("sched/cpufreq, sched/uclamp: Add clamps for FAIR and RT tasks")
Signed-off-by: Qais Yousef <qais.yousef@....com>
---
 kernel/sched/cpufreq_schedutil.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index 48327970552a..93dcea233c65 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -289,6 +289,7 @@ static void sugov_iowait_apply(struct sugov_cpu *sg_cpu, u64 time)
 	 * into the same scale so we can compare.
 	 */
 	boost = (sg_cpu->iowait_boost * sg_cpu->max) >> SCHED_CAPACITY_SHIFT;
+	boost = uclamp_rq_util_with(cpu_rq(sg_cpu->cpu), boost, NULL);
 	if (sg_cpu->util < boost)
 		sg_cpu->util = boost;
 }
-- 
2.25.1