Re: [PATCH] mm/huge_memory: prevent THP_ZERO_PAGE_ALLOC increased twice
From: Andrew Morton
Date: Mon Sep 05 2022 - 16:07:34 EST
On Mon, 5 Sep 2022 21:38:13 +0800 Liu Shixin <liushixin2@xxxxxxxxxx> wrote:
> If two or more threads call get_huge_zero_page concurrently, THP_ZERO_PAGE_ALLOC
> may increased two or more times. But actually, this should only count
> as once since the extra zero pages has been freed.
Well, for better of for worse,
Documentation/admin-guide/mm/transhuge.rst says
thp_zero_page_alloc
is incremented every time a huge zero page is
successfully allocated. It includes allocations which where
dropped due race with other allocation. Note, it doesn't count
every map of the huge zero page, only its allocation.
If you think this interprtation should be changed then please explain
why, and let's be sure to update the documentation accordingly.