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[47.88.44.37]) by mx.google.com with ESMTPS id h11si125249pls.374.2019.06.13.10.13.29 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 13 Jun 2019 10:13:31 -0700 (PDT) Received-SPF: pass (google.com: domain of yang.shi@linux.alibaba.com designates 47.88.44.37 as permitted sender) client-ip=47.88.44.37; Authentication-Results: mx.google.com; spf=pass (google.com: domain of yang.shi@linux.alibaba.com designates 47.88.44.37 as permitted sender) smtp.mailfrom=yang.shi@linux.alibaba.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=alibaba.com X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R591e4;CH=green;DM=||false|;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e07417;MF=yang.shi@linux.alibaba.com;NM=1;PH=DS;RN=11;SR=0;TI=SMTPD_---0TU55.Xp_1560446003; Received: from US-143344MP.local(mailfrom:yang.shi@linux.alibaba.com fp:SMTPD_---0TU55.Xp_1560446003) by smtp.aliyun-inc.com(127.0.0.1); Fri, 14 Jun 2019 01:13:26 +0800 Subject: Re: [v3 PATCH 2/4] mm: move mem_cgroup_uncharge out of __page_cache_release() To: "Kirill A. Shutemov" Cc: ktkhai@virtuozzo.com, kirill.shutemov@linux.intel.com, hannes@cmpxchg.org, mhocko@suse.com, hughd@google.com, shakeelb@google.com, rientjes@google.com, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <1560376609-113689-1-git-send-email-yang.shi@linux.alibaba.com> <1560376609-113689-3-git-send-email-yang.shi@linux.alibaba.com> <20190613113943.ahmqpezemdbwgyax@box> From: Yang Shi Message-ID: <2909ce59-86ba-ea0b-479f-756020fb32af@linux.alibaba.com> Date: Thu, 13 Jun 2019 10:13:19 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 MIME-Version: 1.0 In-Reply-To: <20190613113943.ahmqpezemdbwgyax@box> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 6/13/19 4:39 AM, Kirill A. Shutemov wrote: > 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? So far a quick search shows NULL_COMPOUND_DTOR is not used by any type of compound page. The HugeTLB code sets destructor to NULL_COMPOUND_DTOR when freeing hugetlb pages via hugetlb specific destructor. The prep_new_page() would call prep_compound_page() if __GFP_COMP is used, which sets dtor to COMPOUND_PAGE_DTOR by default.  Just hugetlb and THP set their specific dtors. And, it looks __put_compound_page() doesn't check if dtor is NULL or not at all. >