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    SubjectRe: [PATCH 18/25] Do not disable interrupts in free_page_mlock()
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    On Mon, 2009-04-20 at 23:20 +0100, Mel Gorman wrote:
    > free_page_mlock() tests and clears PG_mlocked using locked versions of the
    > bit operations. If set, it disables interrupts to update counters and this
    > happens on every page free even though interrupts are disabled very shortly
    > afterwards a second time. This is wasteful.
    >
    > This patch splits what free_page_mlock() does. The bit check is still
    > made. However, the update of counters is delayed until the interrupts are
    > disabled and the non-lock version for clearing the bit is used. One potential
    > weirdness with this split is that the counters do not get updated if the
    > bad_page() check is triggered but a system showing bad pages is getting
    > screwed already.
    >
    > Signed-off-by: Mel Gorman <mel@csn.ul.ie>
    > Reviewed-by: Christoph Lameter <cl@linux-foundation.org>

    Reviewed-by: Pekka Enberg <penberg@cs.helsinki.fi>

    > ---
    > mm/internal.h | 11 +++--------
    > mm/page_alloc.c | 8 +++++++-
    > 2 files changed, 10 insertions(+), 9 deletions(-)
    >
    > diff --git a/mm/internal.h b/mm/internal.h
    > index 987bb03..58ec1bc 100644
    > --- a/mm/internal.h
    > +++ b/mm/internal.h
    > @@ -157,14 +157,9 @@ static inline void mlock_migrate_page(struct page *newpage, struct page *page)
    > */
    > static inline void free_page_mlock(struct page *page)
    > {
    > - if (unlikely(TestClearPageMlocked(page))) {
    > - unsigned long flags;
    > -
    > - local_irq_save(flags);
    > - __dec_zone_page_state(page, NR_MLOCK);
    > - __count_vm_event(UNEVICTABLE_MLOCKFREED);
    > - local_irq_restore(flags);
    > - }

    Maybe add a VM_BUG_ON(!PageMlocked(page))?

    > + __ClearPageMlocked(page);
    > + __dec_zone_page_state(page, NR_MLOCK);
    > + __count_vm_event(UNEVICTABLE_MLOCKFREED);
    > }
    >
    > #else /* CONFIG_HAVE_MLOCKED_PAGE_BIT */



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