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, a...@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 <iamjoonsoo....@lge.com> > >> 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 <iamjoonsoo....@lge.com> > >> Cc: Vlastimil Babka <vba...@suse.cz> > >> Cc: David Rientjes <rient...@google.com> > >> Cc: Minchan Kim <minc...@kernel.org> > >> Cc: Michal Nazarewicz <min...@mina86.com> > >> Cc: Naoya Horiguchi <n-horigu...@ah.jp.nec.com> > >> Cc: Christoph Lameter <c...@linux.com> > >> Cc: Rik van Riel <r...@redhat.com> > >> Cc: Mel Gorman <mgor...@suse.de> > >> Cc: Zhang Yanfei <zhangyan...@cn.fujitsu.com> > >> Signed-off-by: Andrew Morton <a...@linux-foundation.org> > > Acked-by: Vlastimil Babka <vba...@suse.cz> > > 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 majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
