From: Yisheng Xie <xieyisheng1@xxxxxxxxxx> Subject: mm/compaction: ignore block suitable after check large free page By reviewing code, I find that if the migrate target is a large free page and we ignore suitable, it may splite large target free page into smaller block which is not good for defrag. So move the ignore block suitable after check large free page. As Vlastimil pointed out in RFC version that this patch is just based on logical analyses which might be better for future-proofing the function and it is most likely won't have any visible effect right now, for direct compaction shouldn't have to be called if there's a >=pageblock_order page already available. Link: http://lkml.kernel.org/r/1489490743-5364-1-git-send-email-xieyisheng1@xxxxxxxxxx Signed-off-by: Yisheng Xie <xieyisheng1@xxxxxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxx> Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Cc: Minchan Kim <minchan@xxxxxxxxxx> Cc: Hanjun Guo <guohanjun@xxxxxxxxxx> Cc: Xishi Qiu <qiuxishi@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/compaction.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff -puN mm/compaction.c~mm-compaction-ignore-block-suitable-after-check-large-free-page mm/compaction.c --- a/mm/compaction.c~mm-compaction-ignore-block-suitable-after-check-large-free-page +++ a/mm/compaction.c @@ -992,9 +992,6 @@ isolate_migratepages_range(struct compac static bool suitable_migration_target(struct compact_control *cc, struct page *page) { - if (cc->ignore_block_suitable) - return true; - /* If the page is a large free page, then disallow migration */ if (PageBuddy(page)) { /* @@ -1006,6 +1003,9 @@ static bool suitable_migration_target(st return false; } + if (cc->ignore_block_suitable) + return true; + /* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */ if (migrate_async_suitable(get_pageblock_migratetype(page))) return true; _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
