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 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 D05FCC433DB for ; Thu, 4 Feb 2021 13:42:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9B02F64F51 for ; Thu, 4 Feb 2021 13:42:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236402AbhBDNls (ORCPT ); Thu, 4 Feb 2021 08:41:48 -0500 Received: from mx2.suse.de ([195.135.220.15]:54716 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236391AbhBDNkO (ORCPT ); Thu, 4 Feb 2021 08:40:14 -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=1612445966; 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=H0iQZN9iBmT3QwxhzQGnFSuWS/L+fw1WcnDMqXjE4sk=; b=mlbFQKAjZNJBkGo4WGSDEqnrJ5Pl4vQ0Xceo5aT+AhaeGPnRgitRceRm3Nthy4aoSRqWhx 23qF+PYgNK2ZNRMB2Y797rPr3jkRB7IAyUY2ldM+JEzuhz+2nLuHMPVmtl/st6Ly3gM6CS qXNuDRYyjC0oT8jpFxizSuPAOV/dYfA= Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 1AD66AF24; Thu, 4 Feb 2021 13:39:26 +0000 (UTC) Date: Thu, 4 Feb 2021 14:39:25 +0100 From: Michal Hocko To: Johannes Weiner Cc: Andrew Morton , Tejun Heo , Roman Gushchin , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH 4/7] cgroup: rstat: support cgroup1 Message-ID: References: <20210202184746.119084-1-hannes@cmpxchg.org> <20210202184746.119084-5-hannes@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210202184746.119084-5-hannes@cmpxchg.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 02-02-21 13:47:43, Johannes Weiner wrote: > Rstat currently only supports the default hierarchy in cgroup2. In > order to replace memcg's private stats infrastructure - used in both > cgroup1 and cgroup2 - with rstat, the latter needs to support cgroup1. > > The initialization and destruction callbacks for regular cgroups are > already in place. Remove the cgroup_on_dfl() guards to handle cgroup1. > > The initialization of the root cgroup is currently hardcoded to only > handle cgrp_dfl_root.cgrp. Move those callbacks to cgroup_setup_root() > and cgroup_destroy_root() to handle the default root as well as the > various cgroup1 roots we may set up during mounting. > > The linking of css to cgroups happens in code shared between cgroup1 > and cgroup2 as well. Simply remove the cgroup_on_dfl() guard. > > Linkage of the root css to the root cgroup is a bit trickier: per > default, the root css of a subsystem controller belongs to the default > hierarchy (i.e. the cgroup2 root). When a controller is mounted in its > cgroup1 version, the root css is stolen and moved to the cgroup1 root; > on unmount, the css moves back to the default hierarchy. Annotate > rebind_subsystems() to move the root css linkage along between roots. I am not familiar with rstat API and from this patch it is not really clear to me how does it deal with memcg v1 use_hierarchy oddness. -- Michal Hocko SUSE Labs