Re: vmstat: On demand vmstat workers V8

From: Christoph Lameter
Date: Tue Jul 29 2014 - 11:22:30 EST

On Tue, 29 Jul 2014, Tejun Heo wrote:

> I'm not sure that's a viable way forward. It's not like we can
> readily trigger the problematic cases which can lead to long pauses
> during cpu down. Besides, we need the distinction at the API level,
> which is the whole point of this. The best way probably is converting
> all the correctness ones (these are the minorities) over to
> queue_work_on() so that the per-cpu requirement is explicit.

Ok so we would need this fix to avoid the message:

Subject: vmstat: use schedule_delayed_work_on to avoid false positives

It seems that schedule_delayed_work_on will check for preemption even
though none can occur. schedule_delayed_work_on will not do that. So
use that function to suppress false positives.

Signed-off-by: Christoph Lameter <cl@xxxxxxxxx>

Index: linux/mm/vmstat.c
--- linux.orig/mm/vmstat.c 2014-07-29 10:14:42.356988271 -0500
+++ linux/mm/vmstat.c 2014-07-29 10:18:28.205920997 -0500
@@ -1255,7 +1255,8 @@ static void vmstat_update(struct work_st
* to occur in the future. Keep on running the
* update worker thread.
- schedule_delayed_work(this_cpu_ptr(&vmstat_work),
+ schedule_delayed_work_on(smp_processor_id(),
+ this_cpu_ptr(&vmstat_work),
else {
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