scx: Pick an idle cpu when select runqueue with WF_EXEC

If the caller of select_task_rq_scx() calls with WF_EXEC, it's a valuable balancing opportunity to perform task migration. Although runqueue can't dictate where the task is going to run, we can still take advantage of this good opportunity by selecting an idle core, rather than doing nothing. Signed-off-by: I Hsin Cheng <[email protected]>
sched-ext · Jun 13, 2024 · 445b763 · 445b763
1 parent 25c10e0
commit 445b763
Showing 1 changed file with 4 additions and 2 deletions.
diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
@@ -3107,8 +3107,10 @@ static int select_task_rq_scx(struct task_struct *p, int prev_cpu, int wake_flag
 	 * which can decide to preempt self to force it through the regular
 	 * scheduling path.
 	 */
-	if (unlikely(wake_flags & WF_EXEC))
-		return prev_cpu;
+	if (unlikely(wake_flags & WF_EXEC)) {
+		int idle_cpu = scx_pick_idle_cpu(p->cpus_ptr, SCX_PICK_IDLE_CORE);
+		return cpu;
+	}
 
 	if (SCX_HAS_OP(select_cpu)) {
 		s32 cpu;