Re: vmstat: On demand vmstat workers V8

[Christoph Lameter <cl@gentwo.org>]

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@linux.com>

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),
 			round_jiffies_relative(sysctl_stat_interval));
 	else {
 		/*