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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id B2B14C433EF for ; Sun, 3 Apr 2022 06:56:52 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 1CF6E6B0072; Sun, 3 Apr 2022 02:56:42 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 1588B6B0073; Sun, 3 Apr 2022 02:56:42 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id F3AD46B0074; Sun, 3 Apr 2022 02:56:41 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0149.hostedemail.com [216.40.44.149]) by kanga.kvack.org (Postfix) with ESMTP id DFF0A6B0072 for ; Sun, 3 Apr 2022 02:56:41 -0400 (EDT) Received: from smtpin17.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 9C3841831C2B5 for ; Sun, 3 Apr 2022 06:56:31 +0000 (UTC) X-FDA: 79314659382.17.1D527B1 Received: from mail-io1-f44.google.com (mail-io1-f44.google.com [209.85.166.44]) by imf10.hostedemail.com (Postfix) with ESMTP id 3756BC002A for ; Sun, 3 Apr 2022 06:56:31 +0000 (UTC) Received: by mail-io1-f44.google.com with SMTP id e22so7747450ioe.11 for ; Sat, 02 Apr 2022 23:56:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=LZlimpDrEHgO1rzyCYuAbLljxvciHy4QdNJs4xVtrnk=; b=T2EKk7dyMep8/29cdvnmpJvSBhC3tVejpCx/rLNsKf9qKNg480LjqMQQCRXV1WS/ql IiF4bR7DYMvv35us0w7WT1RPk7OpoLdrERvZ8VyxZJqHoBllBNyHAYErlPDEkLB+DHQN pqmkgvAu33MWBs0sIXCOx4fkIX797PCMn7wSpeVMYSEIROsVlttHatLTe/nIo46c5Yu9 +PI1uA1Pynxd42/t/8MA5rtp2aNcmszrbKSoR5yHjyZfvqumvyp6bSGaB3AGan996wek XoIdhE2QCNIGkDF/ozpMGNF1ex5zm1Zqts+fajdYUF28OEIrsXf5yYKjIK5jzzYybDaa 3idg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=LZlimpDrEHgO1rzyCYuAbLljxvciHy4QdNJs4xVtrnk=; b=GxxzbMrAp1FH9FJy3y/CvQeSDrWNyz1Ysc8wnjEosVt9KbXGZVO/KyEnyDLXEwEFbn ubZmr43wVc1ABK2oLUkdcHfuB1Y1zjl9AvCWpKm175ATJWY5wX7D2UDC5ta1CTG8Nf+S KjZsZ93OHUt6vD4ZnPXsuO+7krR5jBWPDJCiXzYk3W4lCcygZxLPDgwBb5a0FAboGR85 wWg2+IRi2lfTJriTAMgha+jMFjQHX032GR5adVAsIdVP8fMUL2rz/WBflcKGyU0I55nB 1xczhg677bJQNP2KLXoPqpzgQ5/CpnFXw3snq4/peacP9zlOuzj3FFB8yE6538b9bpPv MXgA== X-Gm-Message-State: AOAM530lw5PrLuhxB1FgndEZFZ+KjxslND0M2UNrzrJEsBScssCgZ/97 YYKUESgbjSNgM7JMgMWNroNRPXcX4yRJlsugv6eZFA== X-Google-Smtp-Source: ABdhPJzb5mBXYffh2qbyaAwkzrHxSsPGl5iPs/oVvkZeOgVaq4/cqjWLGtERImQrJF6BNnSrg/zcLtNNEsH2s3lfa5Y= X-Received: by 2002:a05:6602:2c52:b0:646:2488:a9a0 with SMTP id x18-20020a0566022c5200b006462488a9a0mr3051360iov.130.1648968990332; Sat, 02 Apr 2022 23:56:30 -0700 (PDT) MIME-Version: 1.0 References: <20220331084151.2600229-1-yosryahmed@google.com> <87y20nzyw4.fsf@yhuang6-desk2.ccr.corp.intel.com> In-Reply-To: <87y20nzyw4.fsf@yhuang6-desk2.ccr.corp.intel.com> From: Wei Xu Date: Sat, 2 Apr 2022 23:56:19 -0700 Message-ID: Subject: Re: [PATCH resend] memcg: introduce per-memcg reclaim interface To: "Huang, Ying" Cc: Michal Hocko , Yosry Ahmed , Johannes Weiner , Shakeel Butt , Andrew Morton , David Rientjes , Tejun Heo , Zefan Li , Roman Gushchin , cgroups@vger.kernel.org, linux-doc@vger.kernel.org, Linux Kernel Mailing List , Linux MM , Jonathan Corbet , Yu Zhao , Dave Hansen , Greg Thelen Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 3756BC002A X-Stat-Signature: cnf1hq1a6jmdbcbxtg6urwe8uwjktmtd X-Rspam-User: Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=google.com header.s=20210112 header.b=T2EKk7dy; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf10.hostedemail.com: domain of weixugc@google.com designates 209.85.166.44 as permitted sender) smtp.mailfrom=weixugc@google.com X-HE-Tag: 1648968991-549583 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: On Sat, Apr 2, 2022 at 1:13 AM Huang, Ying wrote: > > Wei Xu writes: > > > On Fri, Apr 1, 2022 at 6:54 AM Michal Hocko wrote: > >> > >> On Thu 31-03-22 08:41:51, Yosry Ahmed wrote: > >> > From: Shakeel Butt > >> > > > [snip] > > >> > Possible Extensions: > >> > -------------------- > >> > > >> > - This interface can be extended with an additional parameter or flags > >> > to allow specifying one or more types of memory to reclaim from (e.g. > >> > file, anon, ..). > >> > > >> > - The interface can also be extended with a node mask to reclaim from > >> > specific nodes. This has use cases for reclaim-based demotion in memory > >> > tiering systens. > >> > > >> > - A similar per-node interface can also be added to support proactive > >> > reclaim and reclaim-based demotion in systems without memcg. > >> > > >> > For now, let's keep things simple by adding the basic functionality. > >> > >> Yes, I am for the simplicity and this really looks like a bare minumum > >> interface. But it is not really clear who do you want to add flags on > >> top of it? > >> > >> I am not really sure we really need a node aware interface for memcg. > >> The global reclaim interface will likely need a different node because > >> we do not want to make this CONFIG_MEMCG constrained. > > > > A nodemask argument for memory.reclaim can be useful for memory > > tiering between NUMA nodes with different performance. Similar to > > proactive reclaim, it can allow a userspace daemon to drive > > memcg-based proactive demotion via the reclaim-based demotion > > mechanism in the kernel. > > I am not sure whether nodemask is a good way for demoting pages between > different types of memory. For example, for a system with DRAM and > PMEM, if specifying DRAM node in nodemask means demoting to PMEM, what > is the meaning of specifying PMEM node? reclaiming to disk? > > In general, I have no objection to the idea in general. But we should > have a clear and consistent interface. Per my understanding the default > memcg interface is for memory, regardless of memory types. The memory > reclaiming means reduce the memory usage, regardless of memory types. > We need to either extending the semantics of memory reclaiming (to > include memory demoting too), or add another interface for memory > demoting. Good point. With the "demote pages during reclaim" patch series, reclaim is already extended to demote pages as well. For example, can_reclaim_anon_pages() returns true if demotion is allowed and shrink_page_list() can demote pages instead of reclaiming pages. Currently, demotion is disabled for memcg reclaim, which I think can be relaxed and also necessary for memcg-based proactive demotion. I'd like to suggest that we extend the semantics of memory.reclaim to cover memory demotion as well. A flag can be used to enable/disable the demotion behavior.