On Tue, Apr 15, 2014 at 11:18:26AM +0200, Vlastimil Babka wrote: > The compaction freepage scanner implementation in isolate_freepages() starts > by taking the current cc->free_pfn value as the first pfn. In a for loop, it > scans from this first pfn to the end of the pageblock, and then subtracts > pageblock_nr_pages from the first pfn to obtain the first pfn for the next > for loop iteration. > > This means that when cc->free_pfn starts at offset X rather than being aligned > on pageblock boundary, the scanner will start at offset X in all scanned > pageblock, ignoring potentially many free pages. Currently this can happen > when > a) zone's end pfn is not pageblock aligned, or > b) through zone->compact_cached_free_pfn with CONFIG_HOLES_IN_ZONE enabled and > a hole spanning the beginning of a pageblock > > This patch fixes the problem by aligning the initial pfn in > isolate_freepages() > to pageblock boundary. This also allows to replace the end-of-pageblock > alignment within the for loop with a simple pageblock_nr_pages increment. > > Signed-off-by: Vlastimil Babka <vba...@suse.cz> > Reported-by: Heesub Shin <heesub.s...@samsung.com> > Cc: Minchan Kim <minc...@kernel.org> > Cc: Mel Gorman <mgor...@suse.de> > Cc: Joonsoo Kim <iamjoonsoo....@lge.com> > Cc: Bartlomiej Zolnierkiewicz <b.zolnier...@samsung.com> > 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> > --- > mm/compaction.c | 22 ++++++++++++---------- > 1 file changed, 12 insertions(+), 10 deletions(-)
Acked-by: Joonsoo Kim <iamjoonsoo....@lge.com> -- 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/
