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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C6BA5ECAAA1 for ; Tue, 30 Aug 2022 07:12:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230429AbiH3HMz (ORCPT ); Tue, 30 Aug 2022 03:12:55 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48416 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230319AbiH3HMw (ORCPT ); Tue, 30 Aug 2022 03:12:52 -0400 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.220.28]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DA5FEAE208; Tue, 30 Aug 2022 00:12:50 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 8A9EA21D09; Tue, 30 Aug 2022 07:12:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1661843569; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=eNLXbzHMzQQl1S+F8MG5tq68Rc2DBXxOVacQ+xIc0Yc=; b=Y/SIOnqS5qw04flbBT0UNoziQh4DL76iydFlVllZY+A0CuuiymDctwvPAVb0iymIopbpe6 KWyit2vQ1FPjzGG9nhgthU0208gtfTPsZ9XcW/V8t71kobfUGPIF+eiPIJinYYrhCvFyX5 qDDPWjg5H/fGrgXOVU/fO5Q+N/WngCo= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 6B9D413ACF; Tue, 30 Aug 2022 07:12:49 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id 8VW6F3G4DWNXLwAAMHmgww (envelope-from ); Tue, 30 Aug 2022 07:12:49 +0000 Date: Tue, 30 Aug 2022 09:12:48 +0200 From: Michal Hocko To: Kairui Song Cc: cgroups@vger.kernel.org, linux-mm@kvack.org, Johannes Weiner , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] mm: memcontrol: remove mem_cgroup_kmem_disabled Message-ID: References: <20220830055949.12640-1-ryncsn@gmail.com> <20220830055949.12640-2-ryncsn@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 30-08-22 15:06:57, Kairui Song wrote: > Michal Hocko 于2022年8月30日周二 14:45写道： > > > > On Tue 30-08-22 13:59:48, Kairui Song wrote: > > > From: Kairui Song > > > > > > There are currently two helpers for checking if cgroup kmem > > > accounting is enabled: > > > > > > - mem_cgroup_kmem_disabled > > > - memcg_kmem_enabled > > > > Yes, this is a bit confusing indeed! > > > > > mem_cgroup_kmem_disabled is a simple helper that returns true if > > > cgroup.memory=nokmem is specified, otherwise returns false. > > > > > > memcg_kmem_enabled is a bit different, it returns true if > > > cgroup.memory=nokmem is not specified and there is at least one > > > non-root cgroup ever created. And once there is any non-root memcg > > > created, it won't go back to return false again. > > > > > > This may help improve performance for some corner use cases where > > > the user enables memory cgroup and kmem accounting globally but never > > > create any cgroup. > > > > > > Considering that corner case is rare, especially nowadays cgroup is > > > widely used as a standard way to organize services. > > > > Is it really that rare? Most configurations would use a default setup, so > > both MEMCG enabled and without nokmem on cmd line yet the memory > > controller is not enabled in their setups. > > Actually I don't have too much confidence saying that as well... but > AFAIK, almost all distros will create a few sub cgroup on boot by the > init (eg. openrc, finit, systemd). Yeah, but do they enable the memory controller as well? Unless I am missing something this will require at least one memcg enabled cgroup to be created. -- Michal Hocko SUSE Labs