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