Messages in this thread Patch in this message | | | Date | Mon, 23 Feb 2009 12:23:32 +0000 | From | Mel Gorman <> | Subject | Re: [PATCH 15/20] Do not disable interrupts in free_page_mlock() |
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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: > > free_page_mlock() tests and clears PG_mlocked. 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. 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> > > --- > > mm/internal.h | 10 ++-------- > > mm/page_alloc.c | 8 +++++++- > > 2 files changed, 9 insertions(+), 9 deletions(-) > > > > diff --git a/mm/internal.h b/mm/internal.h > > index 478223b..b52bf86 100644 > > --- a/mm/internal.h > > +++ b/mm/internal.h > > @@ -155,14 +155,8 @@ 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); > > - } > > + __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
#ifdef CONFIG_UNEVICTABLE_LRU PAGEFLAG(Unevictable, unevictable) __CLEARPAGEFLAG(Unevictable, unevictable) TESTCLEARFLAG(Unevictable, unevictable)
#define MLOCK_PAGES 1 PAGEFLAG(Mlocked, mlocked) __CLEARPAGEFLAG(Mlocked, mlocked) TESTSCFLAG(Mlocked, mlocked)
#else
#define MLOCK_PAGES 0 PAGEFLAG_FALSE(Mlocked) SETPAGEFLAG_NOOP(Mlocked) TESTCLEARFLAG_FALSE(Mlocked)
PAGEFLAG_FALSE(Unevictable) TESTCLEARFLAG_FALSE(Unevictable) SETPAGEFLAG_NOOP(Unevictable) CLEARPAGEFLAG_NOOP(Unevictable) __CLEARPAGEFLAG_NOOP(Unevictable) #endif
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.
> 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) { + __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; -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab
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