On 04/15/2014 05:18 AM, 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>
Acked-by: Rik van Riel <r...@redhat.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/
