Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755065AbaJXC7G (ORCPT ); Thu, 23 Oct 2014 22:59:06 -0400 Received: from LGEMRELSE7Q.lge.com ([156.147.1.151]:55965 "EHLO lgemrelse7q.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751573AbaJXC7D (ORCPT ); Thu, 23 Oct 2014 22:59:03 -0400 X-Original-SENDERIP: 10.177.222.213 X-Original-MAILFROM: iamjoonsoo.kim@lge.com Date: Fri, 24 Oct 2014 12:00:07 +0900 From: Joonsoo Kim To: Vlastimil Babka Cc: linux-kernel@vger.kernel.org, akpm@linux-foundation.org, cl@linux.com, mgorman@suse.de, mina86@mina86.com, minchan@kernel.org, n-horiguchi@ah.jp.nec.com, riel@redhat.com, rientjes@google.com, zhangyanfei@cn.fujitsu.com, mm-commits@vger.kernel.org Subject: Re: + mm-compaction-avoid-premature-range-skip-in-isolate_migratepages_range.patch added to -mm tree Message-ID: <20141024030006.GC15243@js1304-P5Q-DELUXE> References: <543d8d58.g9K7YpzF5ZOXeQqj%akpm@linux-foundation.org> <20141023081543.GB7598@js1304-P5Q-DELUXE> <5448BED1.40909@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5448BED1.40909@suse.cz> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Oct 23, 2014 at 10:39:45AM +0200, Vlastimil Babka wrote: > On 10/23/2014 10:15 AM, Joonsoo Kim wrote: > > On Tue, Oct 14, 2014 at 01:53:44PM -0700, akpm@linux-foundation.org wrote: > >> > >> The patch titled > >> Subject: mm/compaction.c: avoid premature range skip in isolate_migratepages_range > >> has been added to the -mm tree. Its filename is > >> mm-compaction-avoid-premature-range-skip-in-isolate_migratepages_range.patch > >> > >> This patch should soon appear at > >> http://ozlabs.org/~akpm/mmots/broken-out/mm-compaction-avoid-premature-range-skip-in-isolate_migratepages_range.patch > >> and later at > >> http://ozlabs.org/~akpm/mmotm/broken-out/mm-compaction-avoid-premature-range-skip-in-isolate_migratepages_range.patch > >> > >> Before you just go and hit "reply", please: > >> a) Consider who else should be cc'ed > >> b) Prefer to cc a suitable mailing list as well > >> c) Ideally: find the original patch on the mailing list and do a > >> reply-to-all to that, adding suitable additional cc's > >> > >> *** Remember to use Documentation/SubmitChecklist when testing your code *** > >> > >> The -mm tree is included into linux-next and is updated > >> there every 3-4 working days > >> > >> ------------------------------------------------------ > >> From: Joonsoo Kim > >> Subject: mm/compaction.c: avoid premature range skip in isolate_migratepages_range > >> > >> commit edc2ca612496 ("mm, compaction: move pageblock checks up from > >> isolate_migratepages_range()") commonizes isolate_migratepages variants > >> and make them use isolate_migratepages_block(). > >> > >> isolate_migratepages_block() could stop the execution when enough pages > >> are isolated, but, there is no code in isolate_migratepages_range() to > >> handle this case. In the result, even if isolate_migratepages_block() > >> returns prematurely without checking all pages in the range, > >> > >> isolate_migratepages_block() is called repeately on the following > >> pageblock and some pages in the previous range are skipped to check. > >> Then, CMA is failed frequently due to this fact. > >> > >> To fix this problem, this patch let isolate_migratepages_range() know the > >> situation that enough pages are isolated and stop the isolation in that > >> case. > >> > >> Note that isolate_migratepages() has no such problem, because, it always > >> stops the isolation after just one call of isolate_migratepages_block(). > >> > >> Signed-off-by: Joonsoo Kim > >> Cc: Vlastimil Babka > >> Cc: David Rientjes > >> Cc: Minchan Kim > >> Cc: Michal Nazarewicz > >> Cc: Naoya Horiguchi > >> Cc: Christoph Lameter > >> Cc: Rik van Riel > >> Cc: Mel Gorman > >> Cc: Zhang Yanfei > >> Signed-off-by: Andrew Morton > > Acked-by: Vlastimil Babka > > Sorry for the trouble. But I think a more robust and future-proof fix > would be a check such as: if (pfn < block_end_pfn) break; > This should catch any reason where isolate_migratepages_block() did not > finish whole pageblock, and which was not fatal enough to return pfn==0. > However currently this seems to happen only due to isolating too much, > so your patch should work. > So it's up to you if you want to make the check more generic now, or > later after this bug is fixed for 3.18. 'if (pfn < block_end_pfn) break;' has one problem. If we have enough isolated pages and reach at block_end_pfn, we can't stop with above check. More proper check may be as following. 'if (pfn < block_end_pfn || cc->nr_migratepages == COMPACT_CLUSTER_MAX) break;' But, as you mentioned, there is no case where 'pfn < block_end_pfn' now, so I'd like to remain the patch as is. Thanks. -- 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/