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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id B7496C433F5 for ; Wed, 11 May 2022 07:49:48 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 45DB06B0073; Wed, 11 May 2022 03:49:48 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 40C276B0075; Wed, 11 May 2022 03:49:48 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2D82C6B0078; Wed, 11 May 2022 03:49:48 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 208A26B0073 for ; Wed, 11 May 2022 03:49:48 -0400 (EDT) Received: from smtpin02.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 8FC5B31906 for ; Wed, 11 May 2022 07:49:45 +0000 (UTC) X-FDA: 79452687930.02.DAD7931 Received: from mga18.intel.com (mga18.intel.com [134.134.136.126]) by imf20.hostedemail.com (Postfix) with ESMTP id 7274E1C00AE for ; Wed, 11 May 2022 07:49:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1652255384; x=1683791384; h=message-id:subject:from:to:cc:date:in-reply-to: references:mime-version:content-transfer-encoding; bh=b6gFhgmPfcp/OZxV5AdY/HulAh7d6sjI5KnIRmFjjnE=; b=UQJ8kSCMtE5o42bQhMEWEIMYAunJnlS0lxEeaGipmHHWCtjYaNomCTps RC9kA6uy2pvPdDcOEB40OgiELnW+PT5ysv9TVstL4GWBPCwC6oVss8vHN 98VynDd7iC2Q6ac+0NrmrR4mUNMYSjlGKTmSgGZDuOUuhZNG6dO+D8d+D JbVakGlEHwb76tsAut7fagIlaRg8n1kDbYrSM1jET1/EYUdBh4q99RCe7 Sca4m+t4ChqJY7i2enNoX6uI2pfX+8HWKLU+hzP8pn3Y3l53u2Ona/MGT flgBhnYQzDquSb67/SPq9/wP5e19QvVes2yztA5P7XRoQu0WyC8PX3ILI g==; X-IronPort-AV: E=McAfee;i="6400,9594,10343"; a="251673475" X-IronPort-AV: E=Sophos;i="5.91,216,1647327600"; d="scan'208";a="251673475" Received: from orsmga008.jf.intel.com ([10.7.209.65]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 May 2022 00:49:41 -0700 X-IronPort-AV: E=Sophos;i="5.91,216,1647327600"; d="scan'208";a="593991837" Received: from rliu1-mobl1.ccr.corp.intel.com ([10.254.213.20]) by orsmga008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 May 2022 00:49:37 -0700 Message-ID: <68333b21a58604f3fd0e660f1a39921ae22849d8.camel@intel.com> Subject: Re: RFC: Memory Tiering Kernel Interfaces From: "ying.huang@intel.com" To: Wei Xu , "Aneesh Kumar K.V" Cc: Alistair Popple , Yang Shi , Andrew Morton , Dave Hansen , Dan Williams , Linux MM , Greg Thelen , Jagdish Gediya , Linux Kernel Mailing List , Davidlohr Bueso , Michal Hocko , Baolin Wang , Brice Goglin , Feng Tang , Jonathan Cameron , Tim Chen Date: Wed, 11 May 2022 15:49:34 +0800 In-Reply-To: References: <87tua3h5r1.fsf@nvdebian.thelocal> <875ymerl81.fsf@nvdebian.thelocal> <87fslhhb2l.fsf@linux.ibm.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.38.3-1 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Stat-Signature: t7ifsyyuybm848wrc91iix6mz8x1bpnt X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 7274E1C00AE X-Rspam-User: Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=intel.com header.s=Intel header.b=UQJ8kSCM; dmarc=pass (policy=none) header.from=intel.com; spf=none (imf20.hostedemail.com: domain of ying.huang@intel.com has no SPF policy when checking 134.134.136.126) smtp.mailfrom=ying.huang@intel.com X-HE-Tag: 1652255375-725487 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 Tue, 2022-05-10 at 22:30 -0700, Wei Xu wrote: > On Tue, May 10, 2022 at 4:38 AM Aneesh Kumar K.V > wrote: > > > > Alistair Popple writes: > > > > > Wei Xu writes: > > > > > > > On Thu, May 5, 2022 at 5:19 PM Alistair Popple wrote: > > > > > > > > > > Wei Xu writes: > > > > > > > > > > [...] > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Tiering Hierarchy Initialization > > > > > > > > `==============================' > > > > > > > > > > > > > > > > By default, all memory nodes are in the top tier (N_TOPTIER_MEMORY). > > > > > > > > > > > > > > > > A device driver can remove its memory nodes from the top tier, e.g. > > > > > > > > a dax driver can remove PMEM nodes from the top tier. > > > > > > > > > > > > > > With the topology built by firmware we should not need this. > > > > > > > > > > I agree that in an ideal world the hierarchy should be built by firmware based > > > > > on something like the HMAT. But I also think being able to override this will be > > > > > useful in getting there. Therefore a way of overriding the generated hierarchy > > > > > would be good, either via sysfs or kernel boot parameter if we don't want to > > > > > commit to a particular user interface now. > > > > > > > > > > However I'm less sure letting device-drivers override this is a good idea. How > > > > > for example would a GPU driver make sure it's node is in the top tier? By moving > > > > > every node that the driver does not know about out of N_TOPTIER_MEMORY? That > > > > > could get messy if say there were two drivers both of which wanted their node to > > > > > be in the top tier. > > > > > > > > The suggestion is to allow a device driver to opt out its memory > > > > devices from the top-tier, not the other way around. > > > > > > So how would demotion work in the case of accelerators then? In that > > > case we would want GPU memory to demote to DRAM, but that won't happen > > > if both DRAM and GPU memory are in N_TOPTIER_MEMORY and it seems the > > > only override available with this proposal would move GPU memory into a > > > lower tier, which is the opposite of what's needed there. > > > > How about we do 3 tiers now. dax kmem devices can be registered to > > tier 3. By default all numa nodes can be registered at tier 2 and HBM or > > GPU can be enabled to register at tier 1. ? > > This makes sense. I will send an updated RFC based on the discussions so far. Are these tier number fixed? If so, it appears strange that the smallest tier number is 0 on some machines, but 1 on some other machines. Best Regards, Huang, Ying