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 4D309C433FE for ; Sun, 3 Apr 2022 06:56:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1354735AbiDCG6a (ORCPT ); Sun, 3 Apr 2022 02:58:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53576 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229899AbiDCG62 (ORCPT ); Sun, 3 Apr 2022 02:58:28 -0400 Received: from mail-io1-xd35.google.com (mail-io1-xd35.google.com [IPv6:2607:f8b0:4864:20::d35]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D13F5381B5 for ; Sat, 2 Apr 2022 23:56:31 -0700 (PDT) Received: by mail-io1-xd35.google.com with SMTP id 9so7799224iou.5 for ; Sat, 02 Apr 2022 23:56:31 -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=dpIeHIrMdu038HA2cwRZOyuo7/ONR2w+eqyvYkaECkBxGPeqGg9+7vuZRplSatkN0u MqQbo0VKamqleJL3FieifZMifeLn+I3+P1aQWbeN2whn/AM8FFK7wIjoZRDw0MnxRzLQ DEqBvmd4RH9i/Ig3FfZ+mPtdUe3iMJq9qsPYf6LuCbOzAFvclqZJrZM70m0gb0wCqA7y c9Om80Kb5biwOourOpIzju0k/6FfRnCKnZLY/kfIYMwNqrrpPCcUuJZ1cXDoVRCfpGkV PqAgSNbU0KqIWyAqaMRCaxpR9KoNy6X64FQ9ZNi6NH5YLmkfywYgUGzSNRBiC8lKzmew dNVA== X-Gm-Message-State: AOAM531YoocWz1jIVhnxUcmakJAi9pXVum24bAbcdP89i8B5YAO7tHcG Egi/Xf9o5u7gUGm1zJYmEY8LXVr+CsoJBFibsOJaaQ== 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" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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.