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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,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 990BEC433DF for ; Fri, 16 Oct 2020 10:41:48 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 128AB207F7 for ; Fri, 16 Oct 2020 10:41:48 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 128AB207F7 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=suse.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 7D3A8940008; Fri, 16 Oct 2020 06:41:47 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 733DE900002; Fri, 16 Oct 2020 06:41:47 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 6221B940008; Fri, 16 Oct 2020 06:41:47 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0083.hostedemail.com [216.40.44.83]) by kanga.kvack.org (Postfix) with ESMTP id 2B82B900002 for ; Fri, 16 Oct 2020 06:41:47 -0400 (EDT) Received: from smtpin05.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id C9F20362D for ; Fri, 16 Oct 2020 10:41:46 +0000 (UTC) X-FDA: 77377447812.05.smoke05_090684e2721c Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin05.hostedemail.com (Postfix) with ESMTP id B286F18026586 for ; Fri, 16 Oct 2020 10:41:46 +0000 (UTC) X-HE-Tag: smoke05_090684e2721c X-Filterd-Recvd-Size: 2625 Received: from mx2.suse.de (mx2.suse.de [195.135.220.15]) by imf01.hostedemail.com (Postfix) with ESMTP for ; Fri, 16 Oct 2020 10:41:46 +0000 (UTC) X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 1DCC7AB5C; Fri, 16 Oct 2020 10:41:45 +0000 (UTC) References: <20201014190749.24607-1-rpalethorpe@suse.com> <20201016094702.GA95052@blackbook> User-agent: mu4e 1.4.13; emacs 27.1 From: Richard Palethorpe To: Michal =?utf-8?Q?Koutn=C3=BD?= Cc: Roman Gushchin , ltp@lists.linux.it, Johannes Weiner , Andrew Morton , Shakeel Butt , Christoph Lameter , Michal Hocko , Tejun Heo , Vlastimil Babka , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH] mm: memcg/slab: Stop reparented obj_cgroups from charging root Reply-To: rpalethorpe@suse.de In-reply-to: <20201016094702.GA95052@blackbook> Date: Fri, 16 Oct 2020 11:41:43 +0100 Message-ID: <87sgaesba0.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable 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: Hello Michal, Michal Koutn=C3=BD writes: > Hello. > > On Wed, Oct 14, 2020 at 08:07:49PM +0100, Richard Palethorpe wrote: >> SLAB objects which outlive their memcg are moved to their parent >> memcg where they may be uncharged. However if they are moved to the >> root memcg, uncharging will result in negative page counter values as >> root has no page counters. > Why do you think those are reparented objects? If those are originally > charged in a non-root cgroup, then the charge value should be propagated = up the > hierarchy, including root memcg, so if they're later uncharged in root > after reparenting, it should still break even. (Or did I miss some stock > imbalance?) I traced it and can see they are reparented objects and that the root groups counters are zero (or negative if I run madvise06 multiple times) before a drain takes place. I'm guessing this is because the root group has 'use_hierachy' set to false so that the childs page_counter parents are set to NULL. However I will check, because I'm not sure about either. > > (But the patch seems justifiable to me as objects (not)charged directly to > root memcg may be incorrectly uncharged.) > > Thanks, > Michal --=20 Thank you, Richard.