As described in the split_page function comment, for the non-compound high order page, the sub-pages must be freed individually. If the memcg of the fisrt page is valid, the tail pages cannot be uncharged when be freed. For example, when alloc_pages_exact is used to allocate 1MB continuous physical memory, 2MB is charged(kmemcg is enabled and __GFP_ACCOUNT is set). When make_alloc_exact free the unused 1MB and free_pages_exact free the applied 1MB, actually, only 4KB(one page) is uncharged. Therefore, the memcg of the tail page needs to be set when split page. Signed-off-by: Zhou Guanghui <zhouguanghui1@xxxxxxxxxx> --- mm/page_alloc.c | 1 + 1 file changed, 1 insertion(+) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 3e4b29ee2b1e..3ed783e25c3c 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3310,6 +3310,7 @@ void split_page(struct page *page, unsigned int order) for (i = 1; i < (1 << order); i++) set_page_refcounted(page + i); split_page_owner(page, 1 << order); + split_page_memcg(page, 1 << order); } EXPORT_SYMBOL_GPL(split_page); -- 2.25.0
