From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1D053C31E45 for ; Thu, 13 Jun 2019 17:13:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E0D7521743 for ; Thu, 13 Jun 2019 17:13:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404668AbfFMRNb (ORCPT ); Thu, 13 Jun 2019 13:13:31 -0400 Received: from out30-130.freemail.mail.aliyun.com ([115.124.30.130]:38186 "EHLO out30-130.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404760AbfFMRN2 (ORCPT ); Thu, 13 Jun 2019 13:13:28 -0400 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 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. >