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=-13.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL 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 A11B0C433B4 for ; Thu, 8 Apr 2021 20:29:24 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id EB4CD61151 for ; Thu, 8 Apr 2021 20:29:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org EB4CD61151 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=google.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id CBD8F6B0036; Thu, 8 Apr 2021 16:29:22 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C6CD16B006C; Thu, 8 Apr 2021 16:29:22 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id AC0F56B006E; Thu, 8 Apr 2021 16:29:22 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0116.hostedemail.com [216.40.44.116]) by kanga.kvack.org (Postfix) with ESMTP id 8D1336B0036 for ; Thu, 8 Apr 2021 16:29:22 -0400 (EDT) Received: from smtpin29.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 32B44A741 for ; Thu, 8 Apr 2021 20:29:22 +0000 (UTC) X-FDA: 78010339764.29.C46424D Received: from mail-lf1-f53.google.com (mail-lf1-f53.google.com [209.85.167.53]) by imf26.hostedemail.com (Postfix) with ESMTP id 0616240002DD for ; Thu, 8 Apr 2021 20:29:18 +0000 (UTC) Received: by mail-lf1-f53.google.com with SMTP id r8so6081453lfp.10 for ; Thu, 08 Apr 2021 13:29:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=JKWZkaAxh0POJeezT3yF35pSQ4SUrFeYy/oZPNJwPrY=; b=PVqhoyfl2f2u/ilqwkxpT5t81ZjQ6fxWkKlc9c7/UD8g7alBWP1Zni++NjyRMxKn/x 59fA6xFmvuAtKQmM7EaCGS3h2iAfnFPq4yTuvUg8OCTtOJi3ITULqRYc3BYdW3+UJAYV fsmkZ7aHDcgXgRh3Yz6xBZl/0jYo5y0si1V3grdPkUb5kH0HNrG2dRAWWgttVkGZ0wq+ eKaaxGg1m3BEezNW+GPliAbu3tm0kHN222/w+irUTxfvLu73Yd1WgPD+gmUYs7jBKHBj WVgEuA1U+aFGSZbrELbq5jBqJKM5DqT9aCwZnjXwDLWYBUEyMqk+K9HVIoEWbXpSLgwo GhmA== 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=JKWZkaAxh0POJeezT3yF35pSQ4SUrFeYy/oZPNJwPrY=; b=Ew1EZqYkKBPsFhfQx6LoI1pUZ1CE91mVYQ727HGxAuy/FDd/yOKVkCkVqdHiAkyJhy abFQ/9/L1qHd7/u9Al+/NM9KQ7dqPKNiO9feWfWYfUJcX9nDzDKMmok9ZjhPyEBoNBhe JvRlPV3245XF8K2HWUP787diPjtxcypTVWBoev0xDW0Wv54GqQdrqxHJqfMVh+3mzGOa Akzmm7tDAxFx4soPHEErnXA7tyf4eTpV5PGInJUm2hpZhKKGHiaGHI4Ij02vLBiGLTX/ 7DfdySj47Fl9GxsW4wDne/Efzk6oJY74Ja6B5FuvvOcdxzS6y2JhNRhv/pNHmuF/qvvI dpgw== X-Gm-Message-State: AOAM533/l239u3vHKGYiyF9ER5cfJVPETnbyCe9aru6IUXtqDtxE7X8E fUUCEt/PuGqJolH6GGJ6M8HY/yIpNFx7mCcrLNWadw== X-Google-Smtp-Source: ABdhPJx9BhcY5woXbdg+3daXIYZOm/y17QAIL3rYs3JXjdmHsc5UfF+FCX7i2salJlUPCRTgqHgb0Ec9ZmZyqKWQMD8= X-Received: by 2002:a05:6512:3703:: with SMTP id z3mr7860594lfr.358.1617913759939; Thu, 08 Apr 2021 13:29:19 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Shakeel Butt Date: Thu, 8 Apr 2021 13:29:08 -0700 Message-ID: Subject: Re: [RFC PATCH v1 00/11] Manage the top tier memory in a tiered memory To: Yang Shi Cc: Tim Chen , Michal Hocko , Johannes Weiner , Andrew Morton , Dave Hansen , Ying Huang , Dan Williams , David Rientjes , Linux MM , Cgroups , LKML Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 0616240002DD X-Stat-Signature: brbjcqqqyjwa7y3u8jiyyyx5i9bnagk6 Received-SPF: none (google.com>: No applicable sender policy available) receiver=imf26; identity=mailfrom; envelope-from=""; helo=mail-lf1-f53.google.com; client-ip=209.85.167.53 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1617913758-862358 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 Thu, Apr 8, 2021 at 11:01 AM Yang Shi wrote: > > 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. > Yes that's an extreme way to overcome the issue but we can do less extreme by just (hard) limiting the top tier usage of low priority jobs. > > > > 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. > The low and min limits have semantics similar to the v1's soft limit for this situation i.e. letting the low priority job occupy top tier memory and depending on reclaim to take back the excess top tier memory use of such jobs. I have some thoughts on NUMA node limits which I will share in the other thread.