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=-7.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham 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 70E31C4CECE for ; Thu, 17 Oct 2019 08:07:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4C3C620872 for ; Thu, 17 Oct 2019 08:07:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2408129AbfJQIHK (ORCPT ); Thu, 17 Oct 2019 04:07:10 -0400 Received: from mx1.redhat.com ([209.132.183.28]:55426 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727791AbfJQIHJ (ORCPT ); Thu, 17 Oct 2019 04:07:09 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 80E9B6907A; Thu, 17 Oct 2019 08:07:09 +0000 (UTC) Received: from [10.36.117.42] (ovpn-117-42.ams2.redhat.com [10.36.117.42]) by smtp.corp.redhat.com (Postfix) with ESMTP id 2699D5D70D; Thu, 17 Oct 2019 08:07:07 +0000 (UTC) Subject: Re: [RFC] Memory Tiering To: Dave Hansen , Linux-MM , LKML , "Williams, Dan J" , "Verma, Vishal L" , Wu Fengguang , Huang Ying References: From: David Hildenbrand Organization: Red Hat GmbH Message-ID: <0679872d-3d03-2fa3-5bd2-80f694357203@redhat.com> Date: Thu, 17 Oct 2019 10:07:07 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Thu, 17 Oct 2019 08:07:09 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 16.10.19 22:05, Dave Hansen wrote: > The memory hierarchy is getting more complicated and the kernel is > playing an increasing role in managing the different tiers. A few > different groups of folks described "migration" optimizations they were > doing in this area at LSF/MM earlier this year. One of the questions > folks asked was why autonuma wasn't being used. > > At Intel, the primary new tier that we're looking at is persistent > memory (PMEM). We'd like to be able to use "persistent memory" > *without* using its persistence properties, treating it as slightly > slower DRAM. Keith Busch has some patches to use NUMA migration to > automatically migrate DRAM->PMEM instead of discarding it near the end > of the reclaim process. Huang Ying has some patches which use a > modified autonuma to migrate frequently-used data *back* from PMEM->DRAM. Very interesting topic. I heard similar demand from HPC folks (especially involving other memory types ("tiers")). There, I think you often want to let the application manage that. But of course, for many applications an automatic management might already be beneficial. Am I correct that you are using PMEM in this area along with ZONE_DEVICE and not by giving PMEM to the buddy (add_memory())? > > We've tried to do this all generically so that it is not tied to > persistent memory and can be applied to any memory types in lots of > topologies. > > We've been running this code in various forms for the past few months, > comparing it to pure DRAM and hardware-based caching. The initial > results are encouraging and we thought others might want to take a look > at the code or run their own experiments. We're expecting to post the > individual patches soon. But, until then, the code is available here: > > https://git.kernel.org/pub/scm/linux/kernel/git/vishal/tiering.git > > and is tagged with "tiering-0.2", aka. d8e31e81b1dca9. > > Note that internally folks have been calling this "hmem" which is > terribly easy to confuse with the existing hmm. There are still some > "hmem"'s in the tree, but I don't expect them to live much longer. > -- Thanks, David / dhildenb