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

[Pekka Enberg <penberg@kernel.org>]

On Tue, Nov 22, 2011 at 1:08 PM, Gilad Ben-Yossef <gilad@benyossef.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@benyossef.com>
> Acked-by: Christoph Lameter <cl@linux.com>
> CC: Chris Metcalf <cmetcalf@tilera.com>
> CC: Peter Zijlstra <a.p.zijlstra@chello.nl>
> CC: Frederic Weisbecker <fweisbec@gmail.com>
> CC: Russell King <linux@arm.linux.org.uk>
> CC: linux-mm@kvack.org
> CC: Pekka Enberg <penberg@kernel.org>
> CC: Matt Mackall <mpm@selenic.com>
> CC: Sasha Levin <levinsasha928@gmail.com>
> CC: Rik van Riel <riel@redhat.com>
> CC: Andi Kleen <andi@firstfloor.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@kernel.org>

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