On 2015/10/16 18:06, Xishi Qiu wrote: > __rmqueue_fallback() will change the migratetype of pageblock, > so it is possible that two continuous pageblocks have different > migratetypes. > > When freeing all pages of the two blocks, they will be merged > to 4M, and added to the buddy list which the migratetype is the > first pageblock's. > > If later alloc some pages and split the 4M, the second pageblock > will be added to the buddy list, and the migratetype is the first > pageblock's, so it is different from the its pageblock's. > > That means the page in buddy list's migratetype is different from > the page in pageblock's migratetype. This will make confusion. > > However,if we change the hotpath, it will be performance degradation, > so any better ideas? > How about using get_pfnblock_migratetype() to get the pageblock's migratetype first, and compare them? Thanks, Xishi Qiu > Signed-off-by: Xishi Qiu <qiuxishi@xxxxxxxxxx> > --- > mm/page_alloc.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 48aaf7b..5c91348 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -726,6 +726,9 @@ static inline void __free_one_page(struct page *page, > list_add(&page->lru, &zone->free_area[order].free_list[migratetype]); > out: > zone->free_area[order].nr_free++; > + /* If the range spans two pageblocks, reset the migratetype. */ > + if (order > pageblock_order) > + change_pageblock_range(page, order, migratetype); > } > > static inline int free_pages_check(struct page *page) -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>