Re: [PATCH v2 2/2] mm/memcg: set memcg when split page

[Shakeel Butt]

On Wed, Mar 3, 2021 at 11:57 PM Zhou Guanghui <zhouguanghui1@xxxxxxxxxx> wrote:
>
> 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>

Reviewed-by: Shakeel Butt <shakeelb@xxxxxxxxxx>