From: Vlastimil Babka Date: Tue, 6 May 2014 19:50:03 +0000 (-0700) Subject: mm/compaction: make isolate_freepages start at pageblock boundary X-Git-Tag: omap-for-v3.16/fixes-against-rc1~208^2~7 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=49e068f0b73dd042c186ffa9b420a9943e90389a;p=pandora-kernel.git mm/compaction: make isolate_freepages start at pageblock boundary 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 permits replacing the end-of-pageblock alignment within the for loop with a simple pageblock_nr_pages increment. Signed-off-by: Vlastimil Babka Reported-by: Heesub Shin Acked-by: Minchan Kim Cc: Mel Gorman Acked-by: Joonsoo Kim Cc: Bartlomiej Zolnierkiewicz Cc: Michal Nazarewicz Cc: Naoya Horiguchi Cc: Christoph Lameter Acked-by: Rik van Riel Cc: Dongjun Shin Cc: Sunghwan Yun Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Reading git-diff-tree failed