linux-kernel - [PATCH] sched/fair: ignore cache hotness for SMT migration

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Date:   Mon,  3 Aug 2020 17:06:14 -0700
From:   Josh Don <joshdon@...gle.com>
To:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>
Cc:     Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        linux-kernel@...r.kernel.org, Josh Don <joshdon@...gle.com>
Subject: [PATCH] sched/fair: ignore cache hotness for SMT migration

SMT siblings share caches, so cache hotness should be irrelevant for
cross-sibling migration.

Proposed-by: Venkatesh Pallipadi <venki@...gle.com>
Signed-off-by: Josh Don <joshdon@...gle.com>
---
 kernel/sched/fair.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 2ba8f230feb9..5b203b55bcb2 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7402,6 +7402,9 @@ static int task_hot(struct task_struct *p, struct lb_env *env)
 	if (unlikely(task_has_idle_policy(p)))
 		return 0;
 
+	if ((env->sd->flags & cpu_smt_flags()) == cpu_smt_flags())
+		return 0;
+
 	/*
 	 * Buddy candidates are cache hot:
 	 */
-- 
2.28.0.163.g6104cc2f0b6-goog