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=unavailable 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 68B1DC28CBC for ; Tue, 2 Mar 2021 09:49:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3381F64EF1 for ; Tue, 2 Mar 2021 09:49:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1382578AbhCBJkB (ORCPT ); Tue, 2 Mar 2021 04:40:01 -0500 Received: from mx2.suse.de ([195.135.220.15]:50002 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1838025AbhCBJRu (ORCPT ); Tue, 2 Mar 2021 04:17:50 -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=1614676623; 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=2lTNGUQOU5ZRn8hHITEAj8ERC6Szv7NUv4WYSpUAvfo=; b=ONVwZQZrA45Na87INciY0J/4eHEq8CM4tW4gUsuWgvkwKbb+1pYu/hLH1FaZxKguoGXPoX 8d2fQgFqw877ImT19JUUBURst+EUUkY//7eBxrVGrH6Ms9g7zrKSPB23BQc1uwBlJv/vSm 7usGuaI7NIMf/W7FyuAF+BBJvbLvKhc= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 3C880AFCE; Tue, 2 Mar 2021 09:17:03 +0000 (UTC) Date: Tue, 2 Mar 2021 10:17:02 +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: <20210302013451.118701-1-zhouguanghui1@huawei.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org [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. > +} > + > struct mem_cgroup *lock_page_memcg(struct page *page); > void __unlock_page_memcg(struct mem_cgroup *memcg); > void unlock_page_memcg(struct page *page); > @@ -1291,6 +1297,10 @@ mem_cgroup_print_oom_meminfo(struct mem_cgroup *memcg) > { > } > > +static inline void copy_page_memcg(struct page *dst, struct page *src) > +{ > +} > + > static inline struct mem_cgroup *lock_page_memcg(struct page *page) > { > return NULL; > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 3e4b29ee2b1e..ee0a63dc1c9b 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -3307,8 +3307,10 @@ void split_page(struct page *page, unsigned int order) > VM_BUG_ON_PAGE(PageCompound(page), page); > VM_BUG_ON_PAGE(!page_count(page), page); > > - for (i = 1; i < (1 << order); i++) > + for (i = 1; i < (1 << order); i++) { > set_page_refcounted(page + i); > + copy_page_memcg(page + i, page); > + } > split_page_owner(page, 1 << order); > } > EXPORT_SYMBOL_GPL(split_page); > -- > 2.25.0 > -- Michal Hocko SUSE Labs