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=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 12E16C43381 for ; Tue, 2 Mar 2021 19:50:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C65F964F07 for ; Tue, 2 Mar 2021 19:50:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1581445AbhCBSvd (ORCPT ); Tue, 2 Mar 2021 13:51:33 -0500 Received: from mx2.suse.de ([195.135.220.15]:42628 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1449106AbhCBQE1 (ORCPT ); Tue, 2 Mar 2021 11:04:27 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1614700270; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=pdDWsFQcF7rXCFOv6YgPKx+U/DSX9HDlai1p+dLPtQc=; b=CUKK1D189WviMnFB36MEnc7SszarLzXWujqx5F/zbGbrjbAMHbx+ODykvZMkOihPe4jgPF tNbDp+jlZb+Htf35AEd5RHN2RToqnRoSS4Kvg7KSFayMPDXjmLaI8DiP3AXqO4ZMPHJbD8 mPFJAXJztUY614pfLqEgcN6XgNcqrzE= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 68E73B02E; Tue, 2 Mar 2021 15:51:09 +0000 (UTC) Date: Tue, 2 Mar 2021 16:51:05 +0100 From: Michal Hocko To: Zhou Guanghui Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, wangkefeng.wang@huawei.com, guohanjun@huawei.com, dingtianhong@huawei.com, chenweilong@huawei.com, rui.xiang@huawei.com, Johannes Weiner , Nicholas Piggin Subject: Re: [PATCH] mm/memcg: set memcg when split pages Message-ID: References: <20210302013451.118701-1-zhouguanghui1@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 02-03-21 10:17:03, Michal Hocko wrote: > [Cc Johannes for awareness and fixup Nick's email] > > On Tue 02-03-21 01:34:51, Zhou Guanghui wrote: > > When split page, the memory cgroup info recorded in first page is > > not copied to tail pages. In this case, when the tail pages are > > freed, the uncharge operation is not performed. As a result, the > > usage of this memcg keeps increasing, and the OOM may occur. > > > > So, the copying of first page's memory cgroup info to tail pages > > is needed when split page. > > I was not aware that alloc_pages_exact is used for accounted allocations > but git grep told me otherwise so this is not a theoretical one. Both > users (arm64 and s390 kvm) are quite recent AFAICS. split_page is also > used in dma allocator but I got lost in indirection so I have no idea > whether there are any users there. > > The page itself looks reasonable to me. > > > Signed-off-by: Zhou Guanghui > > Acked-by: Michal Hocko > > Minor nit > > > --- > > include/linux/memcontrol.h | 10 ++++++++++ > > mm/page_alloc.c | 4 +++- > > 2 files changed, 13 insertions(+), 1 deletion(-) > > > > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h > > index e6dc793d587d..c7e2b4421dc1 100644 > > --- a/include/linux/memcontrol.h > > +++ b/include/linux/memcontrol.h > > @@ -867,6 +867,12 @@ void mem_cgroup_print_oom_group(struct mem_cgroup *memcg); > > extern bool cgroup_memory_noswap; > > #endif > > > > +static inline void copy_page_memcg(struct page *dst, struct page *src) > > +{ > > + if (src->memcg_data) > > + dst->memcg_data = src->memcg_data; > > I would just drop the test. The struct page is a single cache line which > is dirty by the reference count so another store will unlikely be > noticeable even when NULL is stored here and you safe a conditional. Disregard this. As Zi Yan mentioned in other reply, we need to keep the check and take a css reference along with transfering the memcg. -- Michal Hocko SUSE Labs