linux-kernel - Re: [PATCH v4 5/5] mm: Only IPI CPUs to drain local pages if they exist

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Date:	Wed, 23 Nov 2011 09:45:10 +0200
From:	Pekka Enberg <penberg@...nel.org>
To:	Gilad Ben-Yossef <gilad@...yossef.com>
Cc:	linux-kernel@...r.kernel.org, Chris Metcalf <cmetcalf@...era.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Russell King <linux@....linux.org.uk>, linux-mm@...ck.org,
	Matt Mackall <mpm@...enic.com>,
	Sasha Levin <levinsasha928@...il.com>,
	Rik van Riel <riel@...hat.com>,
	Andi Kleen <andi@...stfloor.org>, Mel Gorman <mel@....ul.ie>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v4 5/5] mm: Only IPI CPUs to drain local pages if they exist

On Tue, Nov 22, 2011 at 1:08 PM, Gilad Ben-Yossef <gilad@...yossef.com> wrote:
> Calculate a cpumask of CPUs with per-cpu pages in any zone and only send an IPI requesting CPUs to drain these pages to the buddy allocator if they actually have pages when asked to flush.
>
> The code path of memory allocation failure for CPUMASK_OFFSTACK=y config was tested using fault injection framework.
>
> Signed-off-by: Gilad Ben-Yossef <gilad@...yossef.com>
> Acked-by: Christoph Lameter <cl@...ux.com>
> CC: Chris Metcalf <cmetcalf@...era.com>
> CC: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> CC: Frederic Weisbecker <fweisbec@...il.com>
> CC: Russell King <linux@....linux.org.uk>
> CC: linux-mm@...ck.org
> CC: Pekka Enberg <penberg@...nel.org>
> CC: Matt Mackall <mpm@...enic.com>
> CC: Sasha Levin <levinsasha928@...il.com>
> CC: Rik van Riel <riel@...hat.com>
> CC: Andi Kleen <andi@...stfloor.org>

I'm adding Mel and Andrew to CC.

> ---
>  mm/page_alloc.c |   18 +++++++++++++++++-
>  1 files changed, 17 insertions(+), 1 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 9dd443d..a3efdf1 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -1119,7 +1119,23 @@ void drain_local_pages(void *arg)
>  */
>  void drain_all_pages(void)
>  {
> -       on_each_cpu(drain_local_pages, NULL, 1);
> +       int cpu;
> +       struct zone *zone;
> +       cpumask_var_t cpus;
> +       struct per_cpu_pageset *pcp;
> +
> +       if (likely(zalloc_cpumask_var(&cpus, GFP_ATOMIC))) {

__GFP_NOWARN

> +               for_each_online_cpu(cpu) {
> +                       for_each_populated_zone(zone) {
> +                               pcp = per_cpu_ptr(zone->pageset, cpu);
> +                               if (pcp->pcp.count)
> +                                       cpumask_set_cpu(cpu, cpus);
> +               }
> +       }
> +               on_each_cpu_mask(cpus, drain_local_pages, NULL, 1);
> +               free_cpumask_var(cpus);
> +       } else
> +               on_each_cpu(drain_local_pages, NULL, 1);
>  }
>
>  #ifdef CONFIG_HIBERNATION

Acked-by: Pekka Enberg <penberg@...nel.org>
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