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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS autolearn=no 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 69F7EC433E0 for ; Fri, 5 Mar 2021 23:58:44 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id DDE24650AA for ; Fri, 5 Mar 2021 23:58:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DDE24650AA Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 64E636B0006; Fri, 5 Mar 2021 18:58:43 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 625A16B006C; Fri, 5 Mar 2021 18:58:43 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 514396B006E; Fri, 5 Mar 2021 18:58:43 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0019.hostedemail.com [216.40.44.19]) by kanga.kvack.org (Postfix) with ESMTP id 364CA6B0006 for ; Fri, 5 Mar 2021 18:58:43 -0500 (EST) Received: from smtpin28.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id F2B56180ACC20 for ; Fri, 5 Mar 2021 23:58:42 +0000 (UTC) X-FDA: 77887488126.28.F3A710B Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf23.hostedemail.com (Postfix) with ESMTP id 03039A0000FF for ; Fri, 5 Mar 2021 23:58:41 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id DF3DE601FE; Fri, 5 Mar 2021 23:58:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1614988721; bh=HbZT0bF1MsVnxN6BmosWjrgrZCSm028Kpqvom+zo5rA=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=kP9fQL0oxzF4MeLAIlf9r2mjWb0IXmPVbfnY/LAipr6zyaplBjZKHIYvNDiD/vksT MxPzAQpWPcorsIEn0ivLCcIPgk2TU4tCLSY39d/t9fwKXPcwKtiMabmvhE/xlPzKwD Xlb3wWSDeMKoqkni3RpbOJg3TVMfltCCYWcH8+AU= Date: Fri, 5 Mar 2021 15:58:40 -0800 From: Andrew Morton To: Michal Hocko Cc: Zhou Guanghui , linux-kernel@vger.kernel.org, linux-mm@kvack.org, hannes@cmpxchg.org, hughd@google.com, kirill.shutemov@linux.intel.com, npiggin@gmail.com, ziy@nvidia.com, wangkefeng.wang@huawei.com, guohanjun@huawei.com, dingtianhong@huawei.com, chenweilong@huawei.com, rui.xiang@huawei.com Subject: Re: [PATCH v2 2/2] mm/memcg: set memcg when split page Message-Id: <20210305155840.4bb6dea4fb473d9ffbe49c99@linux-foundation.org> In-Reply-To: References: <20210304074053.65527-1-zhouguanghui1@huawei.com> <20210304074053.65527-3-zhouguanghui1@huawei.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 03039A0000FF X-Stat-Signature: kgp1kxs3kq94bso5jo7ckpbet5yo461s Received-SPF: none (linux-foundation.org>: No applicable sender policy available) receiver=imf23; identity=mailfrom; envelope-from=""; helo=mail.kernel.org; client-ip=198.145.29.99 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1614988721-698696 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 Fri, 5 Mar 2021 12:52:52 +0100 Michal Hocko wrote: > On Thu 04-03-21 07:40:53, Zhou Guanghui wrote: > > As described in the split_page function comment, for the non-compound > > high order page, the sub-pages must be freed individually. If the > > memcg of the fisrt page is valid, the tail pages cannot be uncharged > > when be freed. > > > > For example, when alloc_pages_exact is used to allocate 1MB continuous > > physical memory, 2MB is charged(kmemcg is enabled and __GFP_ACCOUNT is > > set). When make_alloc_exact free the unused 1MB and free_pages_exact > > free the applied 1MB, actually, only 4KB(one page) is uncharged. > > > > Therefore, the memcg of the tail page needs to be set when split page. > > > > As already mentioned there are at least two explicit users of > __GFP_ACCOUNT with alloc_exact_pages added recently. It would be good to > mention that explicitly and maybe even mention 7efe8ef274024 resp. > c419621873713 so that it is clear this is not just a theoretical issue. I added : Michel: : : There are at least two explicit users of __GFP_ACCOUNT with : alloc_exact_pages added recently. See 7efe8ef274024 ("KVM: arm64: : Allocate stage-2 pgd pages with GFP_KERNEL_ACCOUNT") and c419621873713 : ("KVM: s390: Add memcg accounting to KVM allocations"), so this is not : just a theoretical issue. And should we cc:stable on this one?