Re: vmstat kthreads

[Christoph Lameter <cl@linux.com>]

On Wed, 19 Jun 2013, Paul E. McKenney wrote:

> > I've just ported them over to 3.10 and they merge (with a small fix
> > due to deferred workqueue API changes) and build. I did not try to run
> > this version though.
> > I'll post them as replies to this message.
> >
> > I'd be happy to rescue them from the "TODO" pile... :-)
>
> Please!  ;-)

Well if we are going into vmstat mods then I'd also like to throw in this
old patch:

Subject: vmstat: Avoid interrupt disable in vm stats loop

There is no need to disable interrupts if we use xchg().

Signed-off-by: Christoph Lameter <cl@linux.com>

Index: linux/mm/vmstat.c
===================================================================
--- linux.orig/mm/vmstat.c	2013-05-20 15:19:28.000000000 -0500
+++ linux/mm/vmstat.c	2013-06-19 10:09:09.954024071 -0500
@@ -445,13 +445,8 @@ void refresh_cpu_vm_stats(int cpu)

 		for (i = 0; i < NR_VM_ZONE_STAT_ITEMS; i++)
 			if (p->vm_stat_diff[i]) {
-				unsigned long flags;
-				int v;
+				int v = xchg(p->vm_stat_diff + i, 0);

-				local_irq_save(flags);
-				v = p->vm_stat_diff[i];
-				p->vm_stat_diff[i] = 0;
-				local_irq_restore(flags);
 				atomic_long_add(v, &zone->vm_stat[i]);
 				global_diff[i] += v;
 #ifdef CONFIG_NUMA

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