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=-4.0 required=3.0 tests=BAYES_00, 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 1BC53C433E2 for ; Wed, 2 Sep 2020 14:59:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E22C62078E for ; Wed, 2 Sep 2020 14:59:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727992AbgIBO7I (ORCPT ); Wed, 2 Sep 2020 10:59:08 -0400 Received: from mx2.suse.de ([195.135.220.15]:46544 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726355AbgIBNxQ (ORCPT ); Wed, 2 Sep 2020 09:53:16 -0400 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 77D7EB630; Wed, 2 Sep 2020 13:53:00 +0000 (UTC) Date: Wed, 2 Sep 2020 15:52:58 +0200 From: Michal Hocko To: Pavel Tatashin Cc: Vlastimil Babka , Roman Gushchin , Bharata B Rao , "linux-mm@kvack.org" , Andrew Morton , Johannes Weiner , Shakeel Butt , Vladimir Davydov , "linux-kernel@vger.kernel.org" , Kernel Team , Yafang Shao , stable , Linus Torvalds , Sasha Levin , Greg Kroah-Hartman , David Hildenbrand Subject: Re: [PATCH v2 00/28] The new cgroup slab memory controller Message-ID: <20200902135258.GH4617@dhcp22.suse.cz> References: <20200127173453.2089565-1-guro@fb.com> <20200130020626.GA21973@in.ibm.com> <20200130024135.GA14994@xps.DHCP.thefacebook.com> <20200813000416.GA1592467@carbon.dhcp.thefacebook.com> <6469324e-afa2-18b4-81fb-9e96466c1bf3@suse.cz> <20200902113204.GD4617@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 02-09-20 08:53:49, Pavel Tatashin wrote: > On Wed, Sep 2, 2020 at 7:32 AM Michal Hocko wrote: > > > > On Wed 02-09-20 11:53:00, Vlastimil Babka wrote: > > > >> > > Thread #2: ccs killer kthread > > > >> > > css_killed_work_fn > > > >> > > cgroup_mutex <- Grab this Mutex > > > >> > > mem_cgroup_css_offline > > > >> > > memcg_offline_kmem.part > > > >> > > memcg_deactivate_kmem_caches > > > >> > > get_online_mems > > > >> > > mem_hotplug_lock <- waits for Thread#1 to get read access > > > > And one more thing. THis has been brought up several times already. > > Maybe I have forgoten but why do we take hotplug locks in this path in > > the first place? Memory hotplug notifier takes slab_mutex so this > > shouldn't be really needed. > > Good point, it seems this lock can be completely removed from > memcg_deactivate_kmem_caches I am pretty sure we have discussed that in the past. But I do not remember the outcome. Either we have concluded that this is indeed the case but nobody came up with a patch or we have hit some obscure issue... Maybe David/Roman rememeber more than I do. -- Michal Hocko SUSE Labs