[tip: sched/core] sched/fair: Ignore cache hotness for SMT migration

[tip-bot2 for Josh Don]

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

Commit-ID:     ec73240b1627cddfd7cef018c7fa1c32e64a721e
Gitweb:        https://git.kernel.org/tip/ec73240b1627cddfd7cef018c7fa1c32e64a721e
Author:        Josh Don <joshdon@xxxxxxxxxx>
AuthorDate:    Tue, 04 Aug 2020 12:34:13 -07:00
Committer:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Wed, 26 Aug 2020 12:41:57 +02:00

sched/fair: Ignore cache hotness for SMT migration

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

Signed-off-by: Josh Don <joshdon@xxxxxxxxxx>
Proposed-by: Venkatesh Pallipadi <venki@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/20200804193413.510651-1-joshdon@xxxxxxxxxx
---
 kernel/sched/fair.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 1a68a05..abdb54e 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7402,6 +7402,10 @@ static int task_hot(struct task_struct *p, struct lb_env *env)
 	if (unlikely(task_has_idle_policy(p)))
 		return 0;
 
+	/* SMT siblings share cache */
+	if (env->sd->flags & SD_SHARE_CPUCAPACITY)
+		return 0;
+
 	/*
 	 * Buddy candidates are cache hot:
 	 */