From: Mel Gorman <mgorman@techsingularity.net>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>,
Matt Fleming <matt@codeblueprint.co.uk>,
Mel Gorman <mgorman@techsingularity.net>,
LKML <linux-kernel@vger.kernel.org>
Subject: [PATCH 3/4] sched: Comment on why sync wakeups try to run on the current CPU
Date: Mon, 18 Dec 2017 09:43:26 +0000 [thread overview]
Message-ID: <20171218094327.19562-4-mgorman@techsingularity.net> (raw)
In-Reply-To: <20171218094327.19562-1-mgorman@techsingularity.net>
The sync wakeup logic in wake_affine_idle deserves a short description.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
kernel/sched/fair.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 392e08b364bd..95b1145bc38d 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5737,6 +5737,11 @@ wake_affine_idle(int this_cpu, int prev_cpu, int sync)
static int
wake_affine_sync(int this_cpu, int sync)
{
+ /*
+ * Consider stacking tasks if it's a sync wakeup and there is only
+ * one task on the runqueue. sync wakesups are expected to sleep
+ * either immediately or shortly after the wakeup.
+ */
if (sync && cpu_rq(this_cpu)->nr_running == 1)
return this_cpu;
--
2.15.0
next prev parent reply other threads:[~2017-12-18 9:43 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-18 9:43 [PATCH 0/4] Reduce scheduler migrations due to wake_affine Mel Gorman
2017-12-18 9:43 ` [PATCH 1/4] sched: Only immediately migrate tasks due to interrupts if prev and target CPUs share cache Mel Gorman
2017-12-18 9:43 ` [PATCH 2/4] sched: Allow a wakee to run on the prev_cpu if it is idle and cache-affine with the waker Mel Gorman
2017-12-18 10:26 ` Peter Zijlstra
2017-12-18 10:56 ` Mel Gorman
2017-12-18 10:59 ` Peter Zijlstra
2017-12-18 9:43 ` Mel Gorman [this message]
2017-12-19 19:06 ` [PATCH 3/4] sched: Comment on why sync wakeups try to run on the current CPU Peter Zijlstra
2017-12-19 20:25 ` Mel Gorman
2017-12-20 4:09 ` Mike Galbraith
2017-12-20 4:21 ` Mike Galbraith
2017-12-18 9:43 ` [PATCH 4/4] sched: Allow tasks to stack with a workqueue on the same CPU Mel Gorman
2017-12-18 10:44 ` Mike Galbraith
2017-12-18 11:25 ` Mel Gorman
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