linux-kernel - Re: [v3 PATCH 2/4] mm: move mem_cgroup_uncharge out of __page_cache

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Message-ID: <20190613113943.ahmqpezemdbwgyax@box>
Date:   Thu, 13 Jun 2019 14:39:43 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Yang Shi <yang.shi@...ux.alibaba.com>
Cc:     ktkhai@...tuozzo.com, kirill.shutemov@...ux.intel.com,
        hannes@...xchg.org, mhocko@...e.com, hughd@...gle.com,
        shakeelb@...gle.com, rientjes@...gle.com,
        akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [v3 PATCH 2/4] mm: move mem_cgroup_uncharge out of
 __page_cache_release()

On Thu, Jun 13, 2019 at 05:56:47AM +0800, Yang Shi wrote:
> The later patch would make THP deferred split shrinker memcg aware, but
> it needs page->mem_cgroup information in THP destructor, which is called
> after mem_cgroup_uncharge() now.
> 
> So, move mem_cgroup_uncharge() from __page_cache_release() to compound
> page destructor, which is called by both THP and other compound pages
> except HugeTLB.  And call it in __put_single_page() for single order
> page.


If I read the patch correctly, it will change behaviour for pages with
NULL_COMPOUND_DTOR. Have you considered it? Are you sure it will not break
anything?

-- 
 Kirill A. Shutemov