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=-7.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_PASS, USER_AGENT_MUTT autolearn=unavailable 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 35917C4360F for ; Tue, 26 Mar 2019 18:37:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 09A502084B for ; Tue, 26 Mar 2019 18:37:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1553625456; bh=1l+ysp6En4nkTtZQ4FEODgS2kaetAOBB0hZYA/G4Eq4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=tx7vxZ+rglFkTNC2+zeS48jqMCAzUm2f08/ARIS8ZlsFjwOkg1LDQn2i0/6jRG7MW d4OECE0EamwMqHctE6p3OO1g5bruJZ38Tu5i/E4FcQ5jnKfDxO73WfLoGqMc7R/dER EK62q5P4D8h3lje427vfy+Dzp0A/qeIF1Am6R0LA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732498AbfCZShe (ORCPT ); Tue, 26 Mar 2019 14:37:34 -0400 Received: from mx2.suse.de ([195.135.220.15]:33676 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1731755AbfCZShe (ORCPT ); Tue, 26 Mar 2019 14:37:34 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 21C3AAC7E; Tue, 26 Mar 2019 18:37:33 +0000 (UTC) Date: Tue, 26 Mar 2019 19:37:31 +0100 From: Michal Hocko To: Yang Shi Cc: mgorman@techsingularity.net, riel@surriel.com, hannes@cmpxchg.org, akpm@linux-foundation.org, dave.hansen@intel.com, keith.busch@intel.com, dan.j.williams@intel.com, fengguang.wu@intel.com, fan.du@intel.com, ying.huang@intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 0/10] Another Approach to Use PMEM as NUMA Node Message-ID: <20190326183731.GV28406@dhcp22.suse.cz> References: <1553316275-21985-1-git-send-email-yang.shi@linux.alibaba.com> <20190326135837.GP28406@dhcp22.suse.cz> <43a1a59d-dc4a-6159-2c78-e1faeb6e0e46@linux.alibaba.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <43a1a59d-dc4a-6159-2c78-e1faeb6e0e46@linux.alibaba.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 26-03-19 11:33:17, Yang Shi wrote: > > > On 3/26/19 6:58 AM, Michal Hocko wrote: > > On Sat 23-03-19 12:44:25, Yang Shi wrote: > > > With Dave Hansen's patches merged into Linus's tree > > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c221c0b0308fd01d9fb33a16f64d2fd95f8830a4 > > > > > > PMEM could be hot plugged as NUMA node now. But, how to use PMEM as NUMA node > > > effectively and efficiently is still a question. > > > > > > There have been a couple of proposals posted on the mailing list [1] [2]. > > > > > > The patchset is aimed to try a different approach from this proposal [1] > > > to use PMEM as NUMA nodes. > > > > > > The approach is designed to follow the below principles: > > > > > > 1. Use PMEM as normal NUMA node, no special gfp flag, zone, zonelist, etc. > > > > > > 2. DRAM first/by default. No surprise to existing applications and default > > > running. PMEM will not be allocated unless its node is specified explicitly > > > by NUMA policy. Some applications may be not very sensitive to memory latency, > > > so they could be placed on PMEM nodes then have hot pages promote to DRAM > > > gradually. > > Why are you pushing yourself into the corner right at the beginning? If > > the PMEM is exported as a regular NUMA node then the only difference > > should be performance characteristics (module durability which shouldn't > > play any role in this particular case, right?). Applications which are > > already sensitive to memory access should better use proper binding already. > > Some NUMA topologies might have quite a large interconnect penalties > > already. So this doesn't sound like an argument to me, TBH. > > The major rationale behind this is we assume the most applications should be > sensitive to memory access, particularly for meeting the SLA. The > applications run on the machine may be agnostic to us, they may be sensitive > or non-sensitive. But, assuming they are sensitive to memory access sounds > safer from SLA point of view. Then the "cold" pages could be demoted to PMEM > nodes by kernel's memory reclaim or other tools without impairing the SLA. > > If the applications are not sensitive to memory access, they could be bound > to PMEM or allowed to use PMEM (nice to have allocation on DRAM) explicitly, > then the "hot" pages could be promoted to DRAM. Again, how is this different from NUMA in general? -- Michal Hocko SUSE Labs