Messages in this thread | | | Date | Fri, 16 Oct 2015 18:12:51 +0800 | From | Xishi Qiu <> | Subject | Re: [PATCH] mm: reset migratetype if the range spans two pageblocks |
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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@huawei.com> > --- > 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)
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