linux-kernel - Re: [PATCH v3] mm/huge_memory: prevent THP_ZERO_PAGE

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Date:   Fri, 9 Sep 2022 15:25:41 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Liu Shixin <liushixin2@...wei.com>
Cc:     "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        <linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
        Kefeng Wang <wangkefeng.wang@...wei.com>
Subject: Re: [PATCH v3] mm/huge_memory: prevent THP_ZERO_PAGE_ALLOC
 increased twice

On Fri, 9 Sep 2022 10:16:53 +0800 Liu Shixin <liushixin2@...wei.com> wrote:

> Since user who read THP_ZERO_PAGE_ALLOC may be more concerned about the
> huge zero pages that are really allocated using for thp and can indicated
> the times of calling huge_zero_page_shrinker. It is misleading to increase
> twice if two threads call get_huge_zero_page concurrently. Don't increase
> the value if the huge page is not really used.
> 

I cant say I really understand the point about
huge_zero_page_shrinker(), so I propose this changelog: 

: A user who reads THP_ZERO_PAGE_ALLOC may be more concerned about the huge
: zero pages that are really allocated for thp.  It is misleading to
: increase THP_ZERO_PAGE_ALLOC twice if two threads call get_huge_zero_page
: concurrently.  Don't increase the value if the huge page is not really
: used.

The patch makes sense to me.  What do others think?