[PATCH] mm: fix vmstat_update to keep scheduling itself on all cores

[PATCH] mm: fix vmstat_update to keep scheduling itself on all cores

[Gilad Ben-Yossef]

We set up per-cpu work structures for vmstat and schedule them on
each cpu when they go online only to re-schedule them on the general
work queue when they first run.

This doesn't seem right - how do we ever guarantee that vmstat_update runs
on all cpus? Either I've missed something or our vm stats are off and per-cpu
pages are not drained as frequently as we think they are.

Fix it by re-scheduling the work item on the same cpu it first ran on.

Tested on x86 on 8 way SMP VM.

Signed-off-by: Gilad Ben-Yossef <gilad@benyossef.com>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: Mel Gorman <mel@csn.ul.ie>
CC: Christoph Lameter <cl@linux.com>
CC: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
CC: Andi Kleen <ak@linux.intel.com>
CC: linux-mm@kvack.org
---

diff --git a/mm/vmstat.c b/mm/vmstat.c
index f600557..b396044 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1144,8 +1144,10 @@ int sysctl_stat_interval __read_mostly = HZ;

 static void vmstat_update(struct work_struct *w)
 {
-	refresh_cpu_vm_stats(smp_processor_id());
-	schedule_delayed_work(&__get_cpu_var(vmstat_work),
+	int cpu = smp_processor_id();
+
+	refresh_cpu_vm_stats(cpu);
+	schedule_delayed_work_on(cpu, &__get_cpu_var(vmstat_work),
 		round_jiffies_relative(sysctl_stat_interval));
 }



--
Gilad Ben-Yossef
Chief Coffee Drinker
gilad@benyossef.com
Israel Cell: +972-52-8260388
US Cell: +1-973-8260388
http://benyossef.com

"If you take a class in large-scale robotics, can you end up in a
situation where the homework eats your dog?"
 -- Jean-Baptiste Queru

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

Re: [PATCH] mm: fix vmstat_update to keep scheduling itself on all cores

[Christoph Lameter]

On Wed, 14 Mar 2012, Gilad Ben-Yossef wrote:

> We set up per-cpu work structures for vmstat and schedule them on
> each cpu when they go online only to re-schedule them on the general
> work queue when they first run.

schedule_delayed_work queues on the current cpu unless the
WQ_UNBOUND flag is set. Which is not set for vmstat_work.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

Re: [PATCH] mm: fix vmstat_update to keep scheduling itself on all cores

[Gilad Ben-Yossef]

On Wed, Mar 14, 2012 at 4:09 PM, Christoph Lameter <cl@linux.com> wrote:
> On Wed, 14 Mar 2012, Gilad Ben-Yossef wrote:
>
>> We set up per-cpu work structures for vmstat and schedule them on
>> each cpu when they go online only to re-schedule them on the general
>> work queue when they first run.
>
> schedule_delayed_work queues on the current cpu unless the
> WQ_UNBOUND flag is set. Which is not set for vmstat_work.

I've missed that. My bad. Sorry for the noise.

Gilad



-- 
Gilad Ben-Yossef
Chief Coffee Drinker
gilad@benyossef.com
Israel Cell: +972-52-8260388
US Cell: +1-973-8260388
http://benyossef.com

"If you take a class in large-scale robotics, can you end up in a
situation where the homework eats your dog?"
 -- Jean-Baptiste Queru

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>