From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with ESMTP id D312C6B004F for ; Mon, 13 Jul 2009 05:33:57 -0400 (EDT) Date: Mon, 13 Jul 2009 10:56:03 +0100 From: Mel Gorman Subject: Re: [PATCH] switch free memory back to MIGRATE_MOVABLE Message-ID: <20090713095602.GA996@csn.ul.ie> References: <20090713023030.GA27269@sli10-desk.sh.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20090713023030.GA27269@sli10-desk.sh.intel.com> Sender: owner-linux-mm@kvack.org To: Shaohua Li Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org List-ID: On Mon, Jul 13, 2009 at 10:30:30AM +0800, Shaohua Li wrote: > When page is back to buddy and its order is bigger than pageblock_order, we can > switch its type to MIGRATE_MOVABLE. This can reduce fragmentation. The patch > has obvious effect when read a block device and then drop caches. > > Signed-off-by: Shaohua Li NAK. There is no point making this check in the free path, it can be left at whatever type it is. rmqueue fallback will already find blocks like this and switch the type again if necessary. The only time you might care is memory off-lining and at that point, you can check if a free page spans the pageblock and if so, ignore the existing migrate type. > --- > mm/page_alloc.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > Index: linux/mm/page_alloc.c > =================================================================== > --- linux.orig/mm/page_alloc.c 2009-07-10 11:36:07.000000000 +0800 > +++ linux/mm/page_alloc.c 2009-07-13 09:25:21.000000000 +0800 > @@ -475,6 +475,15 @@ static inline void __free_one_page(struc > order++; > } > set_page_order(page, order); > + > + if (order >= pageblock_order && migratetype != MIGRATE_MOVABLE) { > + int i; > + > + migratetype = MIGRATE_MOVABLE; > + for (i = 0; i < (1 << (order - pageblock_order)); i++) > + set_pageblock_migratetype(page + > + i * pageblock_nr_pages, MIGRATE_MOVABLE); > + } > list_add(&page->lru, > &zone->free_area[order].free_list[migratetype]); > zone->free_area[order].nr_free++; > -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org