linux-kernel - [tip: sched/core] sched/uclamp: Fix iowait boost escaping uclamp restriction

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Date:   Fri, 28 Jan 2022 07:40:15 -0000
From:   "tip-bot2 for Qais Yousef" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Qais Yousef <qais.yousef@....com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: sched/core] sched/uclamp: Fix iowait boost escaping uclamp restriction

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     d37aee9018e68b0d356195caefbb651910e0bbfa
Gitweb:        https://git.kernel.org/tip/d37aee9018e68b0d356195caefbb651910e0bbfa
Author:        Qais Yousef <qais.yousef@....com>
AuthorDate:    Thu, 16 Dec 2021 22:53:20 
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Thu, 27 Jan 2022 12:57:19 +01:00

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>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Link: https://lore.kernel.org/r/20211216225320.2957053-3-qais.yousef@arm.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 62d98b0..6d65ab6 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;
 }