From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752730AbcJLFsr (ORCPT ); Wed, 12 Oct 2016 01:48:47 -0400 Received: from outbound-smtp10.blacknight.com ([46.22.139.15]:37286 "EHLO outbound-smtp10.blacknight.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751027AbcJLFsh (ORCPT ); Wed, 12 Oct 2016 01:48:37 -0400 Date: Wed, 12 Oct 2016 06:36:03 +0100 From: Mel Gorman To: Minchan Kim Cc: Vlastimil Babka , Andrew Morton , Joonsoo Kim , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Sangseok Lee Subject: Re: [PATCH 1/4] mm: adjust reserved highatomic count Message-ID: <20161012053602.GA22174@techsingularity.net> References: <1475819136-24358-1-git-send-email-minchan@kernel.org> <1475819136-24358-2-git-send-email-minchan@kernel.org> <7ac7c0d8-4b7b-e362-08e7-6d62ee20f4c3@suse.cz> <20161007142919.GA3060@bbox> <20161011041916.GA30973@bbox> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20161011041916.GA30973@bbox> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 11, 2016 at 01:19:16PM +0900, Minchan Kim wrote: > From 4a0b6a74ebf1af7f90720b0028da49e2e2a2b679 Mon Sep 17 00:00:00 2001 > From: Minchan Kim > Date: Thu, 6 Oct 2016 13:38:35 +0900 > Subject: [PATCH] mm: don't steal highatomic pageblock > > In page freeing path, migratetype is racy so that a highorderatomic > page could free into non-highorderatomic free list. If that page > is allocated, VM can change the pageblock from higorderatomic to > something. In that case, highatomic pageblock accounting is broken > so it doesn't work(e.g., VM cannot reserve highorderatomic pageblocks > any more although it doesn't reach 1% limit). > > So, this patch prohibits the changing from highatomic to other type. > It's no problem because MIGRATE_HIGHATOMIC is not listed in fallback > array so stealing will only happen due to unexpected races which is > really rare. Also, such prohibiting keeps highatomic pageblock more > longer so it would be better for highorderatomic page allocation. > > Signed-off-by: Minchan Kim > --- > mm/page_alloc.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 55ad0229ebf3..79853b258211 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -2154,7 +2154,8 @@ __rmqueue_fallback(struct zone *zone, unsigned int order, int start_migratetype) > > page = list_first_entry(&area->free_list[fallback_mt], > struct page, lru); > - if (can_steal) > + if (can_steal && > + get_pageblock_migratetype(page) != MIGRATE_HIGHATOMIC) > steal_suitable_fallback(zone, page, start_migratetype); > > /* Remove the page from the freelists */ > @@ -2555,7 +2556,8 @@ int __isolate_free_page(struct page *page, unsigned int order) > struct page *endpage = page + (1 << order) - 1; > for (; page < endpage; page += pageblock_nr_pages) { > int mt = get_pageblock_migratetype(page); > - if (!is_migrate_isolate(mt) && !is_migrate_cma(mt)) > + if (!is_migrate_isolate(mt) && !is_migrate_cma(mt) > + && mt != MIGRATE_HIGHATOMIC) > set_pageblock_migratetype(page, > MIGRATE_MOVABLE); > } Acked-by: Mel Gorman -- Mel Gorman SUSE Labs