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, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 34C83C433E0 for ; Mon, 8 Mar 2021 08:41:44 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id A1AF6651BC for ; Mon, 8 Mar 2021 08:41:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A1AF6651BC Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 359CB6B00B1; Mon, 8 Mar 2021 03:41:43 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 331116B00B2; Mon, 8 Mar 2021 03:41:43 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 220856B00B3; Mon, 8 Mar 2021 03:41:43 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0018.hostedemail.com [216.40.44.18]) by kanga.kvack.org (Postfix) with ESMTP id 0928A6B00B1 for ; Mon, 8 Mar 2021 03:41:43 -0500 (EST) Received: from smtpin19.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id B287B180AD837 for ; Mon, 8 Mar 2021 08:41:42 +0000 (UTC) X-FDA: 77896063644.19.7404729 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf12.hostedemail.com (Postfix) with ESMTP id 731C6E4 for ; Mon, 8 Mar 2021 08:41:39 +0000 (UTC) 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=1615192901; 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=IQsvUx1bc3HFAYXXFvyw7hGdS+2IRJnswNDb2Qjo34s=; b=PLdDqTyvNh44Ko31OLNkhQ4lo2iW9kZb39drwp7Ug4ZL5qvM0LFz9RcF6zAonW5aAxx5Ok iBhillVC6cvC7rgKI8x9y/+HV379hZA5TU7oXWi8SoPY4mPBzOECsszlW87YDvAkfhRAs8 h+Tnu48JBm7b+qsoVBrrvVXYgCNEENQ= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 02E72AC0C; Mon, 8 Mar 2021 08:41:41 +0000 (UTC) Date: Mon, 8 Mar 2021 09:41:38 +0100 From: Michal Hocko To: Andrew Morton 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: References: <20210304074053.65527-1-zhouguanghui1@huawei.com> <20210304074053.65527-3-zhouguanghui1@huawei.com> <20210305155840.4bb6dea4fb473d9ffbe49c99@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210305155840.4bb6dea4fb473d9ffbe49c99@linux-foundation.org> X-Stat-Signature: hdfzxpm5ird6tufuw1jpahuxx6aiz53k X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 731C6E4 Received-SPF: none (suse.com>: No applicable sender policy available) receiver=imf12; identity=mailfrom; envelope-from=""; helo=mx2.suse.de; client-ip=195.135.220.15 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1615192899-782023 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 05-03-21 15:58:40, Andrew Morton wrote: > 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? Somebody more familiar with iommu dma allocation layer should have a look as well (__iommu_dma_alloc_pages) so that we know whether there are kernels outside of the above two ones mentioned above that need a fix. But in general this sounds like a good fit for the stable tree. -- Michal Hocko SUSE Labs