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 30172C38A2D for ; Wed, 26 Oct 2022 09:20:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233212AbiJZJT6 (ORCPT ); Wed, 26 Oct 2022 05:19:58 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45456 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233145AbiJZJTy (ORCPT ); Wed, 26 Oct 2022 05:19:54 -0400 Received: from smtp-out2.suse.de (smtp-out2.suse.de [IPv6:2001:67c:2178:6::1d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 196DE1DDD6; Wed, 26 Oct 2022 02:19:53 -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-out2.suse.de (Postfix) with ESMTPS id CA11F1F37C; Wed, 26 Oct 2022 09:19:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1666775991; 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=UJSIrhvBIpYg0Q5icEbLoO9eTA3cWeRbn/PlJQxhuBo=; b=VFpME5g2pfkFFViLcZNoofvXS+Tmw4rncRgBETSsWP7403402Z8wRLHmXCaj1s3XAjN4eP dLG+/q7e9UNVbysPDEFoYrwrgmkQOEKHhdUNSXH2h9KO3UeQp5rgTm5Q4o5MfKtD8IfYl0 Bz9yn1QM+zxRckwTPgzjYfLmFfa58rg= 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 A6C7C13A6E; Wed, 26 Oct 2022 09:19:51 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id ZmT+Jbf7WGNcXAAAMHmgww (envelope-from ); Wed, 26 Oct 2022 09:19:51 +0000 Date: Wed, 26 Oct 2022 11:19:50 +0200 From: Michal Hocko To: Feng Tang Cc: Aneesh Kumar K V , Andrew Morton , Johannes Weiner , Tejun Heo , Zefan Li , Waiman Long , "Huang, Ying" , "linux-mm@kvack.org" , "cgroups@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "Hansen, Dave" , "Chen, Tim C" , "Yin, Fengwei" Subject: Re: [PATCH] mm/vmscan: respect cpuset policy during page demotion Message-ID: References: <20221026074343.6517-1-feng.tang@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed 26-10-22 16:00:13, Feng Tang wrote: > On Wed, Oct 26, 2022 at 03:49:48PM +0800, Aneesh Kumar K V wrote: > > On 10/26/22 1:13 PM, Feng Tang wrote: > > > In page reclaim path, memory could be demoted from faster memory tier > > > to slower memory tier. Currently, there is no check about cpuset's > > > memory policy, that even if the target demotion node is not allowd > > > by cpuset, the demotion will still happen, which breaks the cpuset > > > semantics. > > > > > > So add cpuset policy check in the demotion path and skip demotion > > > if the demotion targets are not allowed by cpuset. > > > > > > > What about the vma policy or the task memory policy? Shouldn't we respect > > those memory policy restrictions while demoting the page? > > Good question! We have some basic patches to consider memory policy > in demotion path too, which are still under test, and will be posted > soon. And the basic idea is similar to this patch. For that you need to consult each vma and it's owning task(s) and that to me sounds like something to be done in folio_check_references. Relying on memcg to get a cpuset cgroup is really ugly and not really 100% correct. Memory controller might be disabled and then you do not have your association anymore. This all can get quite expensive so the primary question is, does the existing behavior generates any real issues or is this more of an correctness exercise? I mean it certainly is not great to demote to an incompatible numa node but are there any reasonable configurations when the demotion target node is explicitly excluded from memory policy/cpuset? -- Michal Hocko SUSE Labs