From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pd0-f173.google.com (mail-pd0-f173.google.com [209.85.192.173]) by kanga.kvack.org (Postfix) with ESMTP id 1703C6B0032 for ; Mon, 8 Dec 2014 22:08:53 -0500 (EST) Received: by mail-pd0-f173.google.com with SMTP id ft15so6381635pdb.4 for ; Mon, 08 Dec 2014 19:08:52 -0800 (PST) Received: from lgeamrelo04.lge.com (lgeamrelo04.lge.com. [156.147.1.127]) by mx.google.com with ESMTP id h4si21582817pat.135.2014.12.08.19.08.50 for ; Mon, 08 Dec 2014 19:08:51 -0800 (PST) Date: Tue, 9 Dec 2014 12:09:40 +0900 From: Minchan Kim Subject: Re: [RFC PATCH 2/3] mm: more aggressive page stealing for UNMOVABLE allocations Message-ID: <20141209030939.GD3358@bbox> References: <1417713178-10256-1-git-send-email-vbabka@suse.cz> <1417713178-10256-3-git-send-email-vbabka@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <1417713178-10256-3-git-send-email-vbabka@suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Vlastimil Babka Cc: linux-mm@kvack.org, Joonsoo Kim , linux-kernel@vger.kernel.org, Mel Gorman , Rik van Riel , David Rientjes On Thu, Dec 04, 2014 at 06:12:57PM +0100, Vlastimil Babka wrote: > When allocation falls back to stealing free pages of another migratetype, > it can decide to steal extra pages, or even the whole pageblock in order to > reduce fragmentation, which could happen if further allocation fallbacks > pick a different pageblock. In try_to_steal_freepages(), one of the situations > where extra pages are stolen happens when we are trying to allocate a > MIGRATE_RECLAIMABLE page. > > However, MIGRATE_UNMOVABLE allocations are not treated the same way, although > spreading such allocation over multiple fallback pageblocks is arguably even > worse than it is for RECLAIMABLE allocations. To minimize fragmentation, we > should minimize the number of such fallbacks, and thus steal as much as is > possible from each fallback pageblock. Fair enough. > > This patch thus adds a check for MIGRATE_UNMOVABLE to the decision to steal > extra free pages. When evaluating with stress-highalloc from mmtests, this has > reduced the number of MIGRATE_UNMOVABLE fallbacks to roughly 1/6. The number > of these fallbacks stealing from MIGRATE_MOVABLE block is reduced to 1/3. > > Signed-off-by: Vlastimil Babka Acked-by: Minchan Kim Nit: Please fix comment on try_to_steal_freepages. We don't bias MIGRATE_RECLAIMABLE any more so remove it. Instead, put some words about the policy and why. Thanks. > --- > mm/page_alloc.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 548b072..a14249c 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1098,6 +1098,7 @@ static int try_to_steal_freepages(struct zone *zone, struct page *page, > > if (current_order >= pageblock_order / 2 || > start_type == MIGRATE_RECLAIMABLE || > + start_type == MIGRATE_UNMOVABLE || > page_group_by_mobility_disabled) { > int pages; > > -- > 2.1.2 > > -- > 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 -- Kind regards, Minchan Kim -- 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