[PATCH 1/3] sched/fair: don't migrate task if cookie not match

[Aubrey Li]

Load balance tries to move task from busiest CPU to the destination
CPU. When core scheduling is enabled, if the task's cookie does not
match with the destination CPU's core cookie, this task will be
skipped by this CPU. This mitigates the forced idle time on the
destination CPU.

Signed-off-by: Aubrey Li <aubrey.li@xxxxxxxxxxxxxxx>
---
 kernel/sched/fair.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 4728f5e..ba937b9 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7366,8 +7366,9 @@ int can_migrate_task(struct task_struct *p, struct lb_env *env)
 	 * We do not migrate tasks that are:
 	 * 1) throttled_lb_pair, or
 	 * 2) cannot be migrated to this CPU due to cpus_ptr, or
-	 * 3) running (obviously), or
-	 * 4) are cache-hot on their current CPU.
+	 * 3) task's cookie does not match with this CPU's core cookie
+	 * 4) running (obviously), or
+	 * 5) are cache-hot on their current CPU.
 	 */
 	if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
 		return 0;
@@ -7402,6 +7403,17 @@ int can_migrate_task(struct task_struct *p, struct lb_env *env)
 		return 0;
 	}
 
+#ifdef CONFIG_SCHED_CORE
+	if (sched_core_enabled(cpu_rq(env->dst_cpu))) {
+		/*
+		 * Don't migrate task if task's cookie does not match
+		 * with core cookie
+		 */
+		if (p->core_cookie != cpu_rq(env->dst_cpu)->core->core_cookie)
+			return 0;
+	}
+#endif
+
 	/* Record that we found atleast one task that could run on dst_cpu */
 	env->flags &= ~LBF_ALL_PINNED;
 
-- 
2.7.4

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