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=-15.8 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 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 C6C3EC433E0 for ; Mon, 15 Feb 2021 09:47:58 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 471B464DEC for ; Mon, 15 Feb 2021 09:47:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 471B464DEC 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 B0DEF8D00E7; Mon, 15 Feb 2021 04:47:57 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id A98918D00E6; Mon, 15 Feb 2021 04:47:57 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9869C8D00E7; Mon, 15 Feb 2021 04:47:57 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0210.hostedemail.com [216.40.44.210]) by kanga.kvack.org (Postfix) with ESMTP id 805B78D00E6 for ; Mon, 15 Feb 2021 04:47:57 -0500 (EST) Received: from smtpin17.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 44C22F01B for ; Mon, 15 Feb 2021 09:47:57 +0000 (UTC) X-FDA: 77820025794.17.leaf78_2e14d0d2763a Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin17.hostedemail.com (Postfix) with ESMTP id 2B2FD183DEA80 for ; Mon, 15 Feb 2021 09:47:57 +0000 (UTC) X-HE-Tag: leaf78_2e14d0d2763a X-Filterd-Recvd-Size: 2956 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf27.hostedemail.com (Postfix) with ESMTP for ; Mon, 15 Feb 2021 09:47:56 +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=1613382475; 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=tgPT5P13ZnYUMYX9KeVnDKoSxuQbU0v+VMfCnnxCsVA=; b=pg9Nrs5pHfRxhWPI6aAQKx/oWV5710KNxAtTwHE+ZVl/TEwLWu3Sxz0P9TfOgZbEKp2vKt HcvlbL5NcNjfrfuAAk5VPnz78+HRCbulwyYvRxNx/Q6VYiKVorHekf3UrdIYjl+pmfVKrO M8Fwru0ZPhg8/k5TlqQUm9ez5taN6QM= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 88EA2AC69; Mon, 15 Feb 2021 09:47:55 +0000 (UTC) Date: Mon, 15 Feb 2021 10:47:54 +0100 From: Michal Hocko To: Muchun Song Cc: hannes@cmpxchg.org, vdavydov.dev@gmail.com, akpm@linux-foundation.org, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 4/4] mm: memcontrol: fix swap uncharge on cgroup v2 Message-ID: References: <20210212170159.32153-1-songmuchun@bytedance.com> <20210212170159.32153-4-songmuchun@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210212170159.32153-4-songmuchun@bytedance.com> 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 Sat 13-02-21 01:01:59, Muchun Song wrote: > The swap charges the actual number of swap entries on cgroup v2. > If a swap cache page is charged successful, and then we uncharge > the swap counter. It is wrong on cgroup v2. Because the swap > entry is not freed. Is there any actual problem though? Can you describe the specific scenario please? Swap cache charge life time is a bit tricky and I have to confess I have to relearn it every time I need to understand it. The patch would be much more easier to review if the changelog was much more specific. > Fixes: 2d1c498072de ("mm: memcontrol: make swap tracking an integral part of memory control") > Signed-off-by: Muchun Song > --- > mm/memcontrol.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index c737c8f05992..be6bc5044150 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -6753,7 +6753,7 @@ int mem_cgroup_charge(struct page *page, struct mm_struct *mm, gfp_t gfp_mask) > memcg_check_events(memcg, page); > local_irq_enable(); > > - if (PageSwapCache(page)) { > + if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) && PageSwapCache(page)) { > swp_entry_t entry = { .val = page_private(page) }; > /* > * The swap entry might not get freed for a long time, > -- > 2.11.0 -- Michal Hocko SUSE Labs