linux-kernel - [RFC PATCH 4/7] sched/fair: Dissociate wakeup decisions from SD flag value

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Message-Id: <20191211164401.5013-5-valentin.schneider@arm.com>
Date:   Wed, 11 Dec 2019 16:43:58 +0000
From:   Valentin Schneider <valentin.schneider@....com>
To:     linux-kernel@...r.kernel.org
Cc:     mingo@...hat.com, peterz@...radead.org, vincent.guittot@...aro.org,
        dietmar.eggemann@....com
Subject: [RFC PATCH 4/7] sched/fair: Dissociate wakeup decisions from SD flag value

The CFS wakeup code will only ever go through EAS / its fast path on
"regular" wakeups (i.e. not on forks or execs). These are currently gated
by a check against 'sd_flag', which would be SD_BALANCE_WAKE at wakeup.

However, we now have a flag that explicitly tells us whether a wakeup is a
"regular" one, so hinge those conditions on that flag instead.

Signed-off-by: Valentin Schneider <valentin.schneider@....com>
---
 kernel/sched/fair.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index f0b2b403bebb..30e8d357a24f 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6355,7 +6355,7 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags)
 		sd_flag = SD_BALANCE_EXEC;
 	}
 
-	if (sd_flag & SD_BALANCE_WAKE) {
+	if (wake_flags & WF_TTWU) {
 		record_wakee(p);
 
 		if (sched_energy_enabled()) {
@@ -6396,9 +6396,8 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags)
 	if (unlikely(sd)) {
 		/* Slow path */
 		new_cpu = find_idlest_cpu(sd, p, cpu, prev_cpu, sd_flag);
-	} else if (sd_flag & SD_BALANCE_WAKE) { /* XXX always ? */
+	} else if (wake_flags & WF_TTWU) { /* XXX always ? */
 		/* Fast path */
-
 		new_cpu = select_idle_sibling(p, prev_cpu, new_cpu);
 
 		if (want_affine)
-- 
2.24.0