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=-2.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 5F466C433ED for ; Fri, 9 Apr 2021 20:50:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3820A610E7 for ; Fri, 9 Apr 2021 20:50:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234330AbhDIUu7 (ORCPT ); Fri, 9 Apr 2021 16:50:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55972 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229523AbhDIUu5 (ORCPT ); Fri, 9 Apr 2021 16:50:57 -0400 Received: from mail-ed1-x52e.google.com (mail-ed1-x52e.google.com [IPv6:2a00:1450:4864:20::52e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 16943C061762; Fri, 9 Apr 2021 13:50:37 -0700 (PDT) Received: by mail-ed1-x52e.google.com with SMTP id ba6so8049663edb.1; Fri, 09 Apr 2021 13:50:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=dLgfKnerQa8S9kw5sUyqufs674F+LLwjy+/qpDVrtV4=; b=eG7YO91jFuC/ubBB6P/KKDlp1/jANHGvhdE1wzKPGH887hr0qnx7DTEM+Nzlm7fRXX yfGquzeL43SyeYSFkoFCWTlq4Arhr4oBhMQ7VmqVESTCliFXd3V3x0tK9+ft4EFKTVWL GVgziuqt33WW6aH9R4IRpaviJ1JkPDbpTaRZC1Mb9+8pMredfwJQBbJbQAnkNXzrTIAR fPagOrsF32qg17YyGcicIgblru/hfU1W5BkuDbFUiX/GJTn5Q6kw550M4GB2AHL2wAbt xTgSdIV8f/nhzz3Tn001xKfLjaDrpbo7JLzyfQ6j4tccLZ3LwL7mcD+AJX56oKRyg488 gvxA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=dLgfKnerQa8S9kw5sUyqufs674F+LLwjy+/qpDVrtV4=; b=klfEWEcmfOlGAo9aSCARYVv3f0MmS97AwOGoZcMbEw1JHn3e5wihI9STEnUCyIg9KT GeJV3My54b+Y6cVKnAomdMSxMKMiWvEtU0NNrHdDVLHFwopierPUHS42wbCEg8ct/Jrm GZh75mSiw5KJKbGBvMgw9xj15S9xB7z/REqe9aepxN/3DAqFdZO4PtgtvZmA68Ww+6Wy xYSRC6+tF+DnKcOzyZKNy4kso48P/CRkxyQNtySBqvNP9QFl/x8Rqu50RlUCPP3Mxnbd X0UiOLszpFIQRW8Ob6XjEr3DuTFMH2M2XFFjX4gFE5mzTYYw8cp5g7fVgXr/Cem+KsOA V1+w== X-Gm-Message-State: AOAM530qoezwlr3VERG2MqRHwdaD+ZK/OUNoU5cRzYbWfW+MUkdLgehu Rce2x7DtE6KKToBEB5ay1IMQAh4ZNZLSdwB5LLU= X-Google-Smtp-Source: ABdhPJxGrexh7XQIMbhChYUAHm6t79qHnHYnwzH77BTy3uzmqQaq5H/Byn0HzXRlRxjsz79n2AAvTcSjKFXy2Cy0jdE= X-Received: by 2002:a50:fd12:: with SMTP id i18mr13568238eds.137.1618001435663; Fri, 09 Apr 2021 13:50:35 -0700 (PDT) MIME-Version: 1.0 References: <87eefkxiys.fsf@yhuang6-desk1.ccr.corp.intel.com> In-Reply-To: <87eefkxiys.fsf@yhuang6-desk1.ccr.corp.intel.com> From: Yang Shi Date: Fri, 9 Apr 2021 13:50:24 -0700 Message-ID: Subject: Re: [RFC PATCH v1 00/11] Manage the top tier memory in a tiered memory To: "Huang, Ying" Cc: Shakeel Butt , Tim Chen , Michal Hocko , Johannes Weiner , Andrew Morton , Dave Hansen , Dan Williams , David Rientjes , Linux MM , Cgroups , LKML , Feng Tang Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 8, 2021 at 7:58 PM Huang, Ying wrote: > > Yang Shi writes: > > > On Thu, Apr 8, 2021 at 10:19 AM Shakeel Butt wrote: > >> > >> Hi Tim, > >> > >> On Mon, Apr 5, 2021 at 11:08 AM Tim Chen wrote: > >> > > >> > Traditionally, all memory is DRAM. Some DRAM might be closer/faster than > >> > others NUMA wise, but a byte of media has about the same cost whether it > >> > is close or far. But, with new memory tiers such as Persistent Memory > >> > (PMEM). there is a choice between fast/expensive DRAM and slow/cheap > >> > PMEM. > >> > > >> > The fast/expensive memory lives in the top tier of the memory hierachy. > >> > > >> > Previously, the patchset > >> > [PATCH 00/10] [v7] Migrate Pages in lieu of discard > >> > https://lore.kernel.org/linux-mm/20210401183216.443C4443@viggo.jf.intel.com/ > >> > provides a mechanism to demote cold pages from DRAM node into PMEM. > >> > > >> > And the patchset > >> > [PATCH 0/6] [RFC v6] NUMA balancing: optimize memory placement for memory tiering system > >> > https://lore.kernel.org/linux-mm/20210311081821.138467-1-ying.huang@intel.com/ > >> > provides a mechanism to promote hot pages in PMEM to the DRAM node > >> > leveraging autonuma. > >> > > >> > The two patchsets together keep the hot pages in DRAM and colder pages > >> > in PMEM. > >> > >> Thanks for working on this as this is becoming more and more important > >> particularly in the data centers where memory is a big portion of the > >> cost. > >> > >> I see you have responded to Michal and I will add my more specific > >> response there. Here I wanted to give my high level concern regarding > >> using v1's soft limit like semantics for top tier memory. > >> > >> This patch series aims to distribute/partition top tier memory between > >> jobs of different priorities. We want high priority jobs to have > >> preferential access to the top tier memory and we don't want low > >> priority jobs to hog the top tier memory. > >> > >> Using v1's soft limit like behavior can potentially cause high > >> priority jobs to stall to make enough space on top tier memory on > >> their allocation path and I think this patchset is aiming to reduce > >> that impact by making kswapd do that work. However I think the more > >> concerning issue is the low priority job hogging the top tier memory. > >> > >> The possible ways the low priority job can hog the top tier memory are > >> by allocating non-movable memory or by mlocking the memory. (Oh there > >> is also pinning the memory but I don't know if there is a user api to > >> pin memory?) For the mlocked memory, you need to either modify the > >> reclaim code or use a different mechanism for demoting cold memory. > > > > Do you mean long term pin? RDMA should be able to simply pin the > > memory for weeks. A lot of transient pins come from Direct I/O. They > > should be less concerned. > > > > The low priority jobs should be able to be restricted by cpuset, for > > example, just keep them on second tier memory nodes. Then all the > > above problems are gone. > > To optimize the page placement of a process between DRAM and PMEM, we > want to place the hot pages in DRAM and the cold pages in PMEM. But the > memory accessing pattern changes overtime, so we need to migrate pages > between DRAM and PMEM to adapt to the changing. > > To avoid the hot pages be pinned in PMEM always, one way is to online > the PMEM as movable zones. If so, and if the low priority jobs are > restricted by cpuset to allocate from PMEM only, we may fail to run > quite some workloads as being discussed in the following threads, > > https://lore.kernel.org/linux-mm/1604470210-124827-1-git-send-email-feng.tang@intel.com/ Thanks for sharing the thread. It seems the configuration of movable zone + node bind is not supported very well or need evolve to support new use cases. > > >> > >> Basically I am saying we should put the upfront control (limit) on the > >> usage of top tier memory by the jobs. > > > > This sounds similar to what I talked about in LSFMM 2019 > > (https://lwn.net/Articles/787418/). We used to have some potential > > usecase which divides DRAM:PMEM ratio for different jobs or memcgs > > when I was with Alibaba. > > > > In the first place I thought about per NUMA node limit, but it was > > very hard to configure it correctly for users unless you know exactly > > about your memory usage and hot/cold memory distribution. > > > > I'm wondering, just off the top of my head, if we could extend the > > semantic of low and min limit. For example, just redefine low and min > > to "the limit on top tier memory". Then we could have low priority > > jobs have 0 low/min limit. > > Per my understanding, memory.low/min are for the memory protection > instead of the memory limiting. memory.high is for the memory limiting. Yes, it is not limit. I just misused the term, I actually do mean protection but typed "limit". Sorry for the confusion. > > Best Regards, > Huang, Ying