Messages in this thread | | | Date | Tue, 26 Apr 2011 11:13:58 +0100 | From | Mel Gorman <> | Subject | Re: [PATCH] mm: Check if any page in a pageblock is reserved before marking it MIGRATE_RESERVE |
| |
On Tue, Apr 26, 2011 at 06:49:39PM +0900, KOSAKI Motohiro wrote: > > On Thu, Apr 21, 2011 at 06:34:03PM -0700, John Stultz wrote: > > > From: Arve Hjønnevåg <arve@android.com> > > > > > > This fixes a problem where the first pageblock got marked MIGRATE_RESERVE even > > > though it only had a few free pages. This in turn caused no contiguous memory > > > to be reserved and frequent kswapd wakeups that emptied the caches to get more > > > contiguous memory. > > > > > > CC: Dave Hansen <dave@linux.vnet.ibm.com> > > > CC: Mel Gorman <mgorman@suse.de> > > > CC: Andrew Morton <akpm@linux-foundation.org> > > > Signed-off-by: Arve Hjønnevåg <arve@android.com> > > > Acked-by: Mel Gorman <mel@csn.ul.ie> > > > > > > [This patch was submitted and acked a little over a year ago > > > (see: http://lkml.org/lkml/2010/4/6/172 ), but never seemingly > > > made it upstream. Resending for comments. -jstultz] > > > > > > Signed-off-by: John Stultz <john.stultz@linaro.org> > > > > Whoops, should have spotted it slipped through. FWIW, I'm still happy > > with my Ack being stuck onto it. > > Hehe, No. > > You acked another patch at last year and John taked up old one. Sigh. > Look, correct one has pfn_valid_within(). > http://lkml.org/lkml/2010/4/6/172 >
Bah, you're right thanks for catching that. A pfn_valid_within check is indeed required, particularly on ARM where there can be holes punched within pageblock boundaries. Thanks
> > Subject: [PATCH] mm: Check if any page in a pageblock is reserved before marking it MIGRATE_RESERVE > From: Arve Hjonnevag <arve@android.com> > > This fixes a problem where the first pageblock got marked MIGRATE_RESERVE even > though it only had a few free pages. eg, On current ARM port, The kernel starts > at offset 0x8000 to leave room for boot parameters, and the memory is freed later. > > This in turn caused no contiguous memory to be reserved and frequent kswapd > wakeups that emptied the caches to get more contiguous memory. > > Unfortunatelly, ARM need order-2 allocation for pgd (see arm/mm/pgd.c#pgd_alloc()). > Therefore the issue is not minor nor easy avoidable. > > CC: Andrew Morton <akpm@linux-foundation.org> > Signed-off-by: Arve Hjonnevag <arve@android.com> > Acked-by: Mel Gorman <mel@csn.ul.ie> > Acked-by: Dave Hansen <dave@linux.vnet.ibm.com> > Signed-off-by: John Stultz <john.stultz@linaro.org> > Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> [added a > few explanation] > --- > mm/page_alloc.c | 16 +++++++++++++++- > 1 files changed, 15 insertions(+), 1 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 1d5c189..10d9fa7 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -3282,6 +3282,20 @@ static inline unsigned long wait_table_bits(unsigned long size) > #define LONG_ALIGN(x) (((x)+(sizeof(long))-1)&~((sizeof(long))-1)) > > /* > + * Check if a pageblock contains reserved pages > + */ > +static int pageblock_is_reserved(unsigned long start_pfn) > +{ > + unsigned long end_pfn = start_pfn + pageblock_nr_pages; > + unsigned long pfn; > + > + for (pfn = start_pfn; pfn < end_pfn; pfn++) > + if (!pfn_valid_within(pfn) || PageReserved(pfn_to_page(pfn))) > + return 1; > + return 0; > +} > + > +/* > * Mark a number of pageblocks as MIGRATE_RESERVE. The number > * of blocks reserved is based on min_wmark_pages(zone). The memory within > * the reserve will tend to store contiguous free pages. Setting min_free_kbytes > @@ -3320,7 +3334,7 @@ static void setup_zone_migrate_reserve(struct zone *zone) > continue; > > /* Blocks with reserved pages will never free, skip them. */ > - if (PageReserved(page)) > + if (pageblock_is_reserved(pfn)) > continue; > > block_migratetype = get_pageblock_migratetype(page);
-- Mel Gorman SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |