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    SubjectRe: [PATCH 15/20] Do not disable interrupts in free_page_mlock()
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    On Mon, 2009-02-23 at 12:23 +0000, Mel Gorman wrote:
    > On Mon, Feb 23, 2009 at 10:19:00AM +0100, Peter Zijlstra wrote:
    > > On Sun, 2009-02-22 at 23:17 +0000, Mel Gorman wrote:

    > > > 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);
    > > > - }
    > > > + __dec_zone_page_state(page, NR_MLOCK);
    > > > + __count_vm_event(UNEVICTABLE_MLOCKFREED);
    > > > }
    > >
    > > Its not actually clearing PG_mlocked anymore, so the name is now a tad
    > > misleading.
    > >
    >
    > Really? I see the following

    > So there is a PG_mlocked bit once UNEVITABLE_LRU is set which was the
    > case on the tests I was running. I'm probably missing something silly.

    What I was trying to say was that free_page_mlock() doesn't change the
    page-state after your change, hence the 'free' part of its name is
    misleading.

    > > That said, since we're freeing the page, there ought to not be another
    > > reference to the page, in which case it appears to me we could safely
    > > use the unlocked variant of TestClear*().
    > >
    >
    > Regrettably, unlocked variants do not appear to be defined as such but
    > the following should do the job, right? It applies on top of the current
    > change.
    >
    > diff --git a/mm/internal.h b/mm/internal.h
    > index b52bf86..7f775a1 100644
    > --- a/mm/internal.h
    > +++ b/mm/internal.h
    > @@ -155,6 +155,7 @@ static inline void mlock_migrate_page(struct page *newpage, struct page *page)
    > */
    > static inline void free_page_mlock(struct page *page)
    > {
    VM_BUG_ON(!PageMlocked(page)); ?

    > + __ClearPageMlocked(page);
    > __dec_zone_page_state(page, NR_MLOCK);
    > __count_vm_event(UNEVICTABLE_MLOCKFREED);
    > }
    > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
    > index edac673..8bd0533 100644
    > --- a/mm/page_alloc.c
    > +++ b/mm/page_alloc.c
    > @@ -580,7 +580,7 @@ static void __free_pages_ok(struct page *page, unsigned int order,
    > unsigned long flags;
    > int i;
    > int bad = 0;
    > - int clearMlocked = TestClearPageMlocked(page);
    > + int clearMlocked = PageMlocked(page);
    >
    > for (i = 0 ; i < (1 << order) ; ++i)
    > bad += free_pages_check(page + i);
    > @@ -1040,7 +1040,7 @@ static void free_pcp_page(struct page *page)
    > struct per_cpu_pages *pcp;
    > unsigned long flags;
    > int migratetype;
    > - int clearMlocked = TestClearPageMlocked(page);
    > + int clearMlocked = PageMlocked(page);
    >
    > if (PageAnon(page))
    > page->mapping = NULL;

    Right, that should do.



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