Commit dc824eb8 authored Nov 02, 2020 by Valentin Schneider Committed by Peter Zijlstra Nov 10, 2020

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@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20201102184514.2733-4-valentin.schneider@arm.com

parent 3aef1551

kernel/sched/fair.c

+2 −3

Original line number	Diff line number	Diff line
		@@ -6705,7 +6705,7 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags)
		/* SD_flags and WF_flags share the first nibble */
		int sd_flag = wake_flags & 0xF;

		if (sd_flag & SD_BALANCE_WAKE) {
		if (wake_flags & WF_TTWU) {
		record_wakee(p);

		if (sched_energy_enabled()) {
		@@ -6742,9 +6742,8 @@ 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)