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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 2871AC43441 for ; Mon, 19 Nov 2018 15:49:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E94FD20851 for ; Mon, 19 Nov 2018 15:49:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E94FD20851 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729902AbeKTCNV (ORCPT ); Mon, 19 Nov 2018 21:13:21 -0500 Received: from mga07.intel.com ([134.134.136.100]:48104 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729669AbeKTCNU (ORCPT ); Mon, 19 Nov 2018 21:13:20 -0500 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from fmsmga005.fm.intel.com ([10.253.24.32]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 19 Nov 2018 07:49:22 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,253,1539673200"; d="scan'208";a="281227482" Received: from unknown (HELO localhost.localdomain) ([10.232.112.69]) by fmsmga005.fm.intel.com with ESMTP; 19 Nov 2018 07:49:21 -0800 Date: Mon, 19 Nov 2018 08:46:05 -0700 From: Keith Busch To: Anshuman Khandual Cc: linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, linux-mm@kvack.org, Greg Kroah-Hartman , Rafael Wysocki , Dave Hansen , Dan Williams Subject: Re: [PATCH 2/7] node: Add heterogenous memory performance Message-ID: <20181119154604.GC23062@localhost.localdomain> References: <20181114224921.12123-2-keith.busch@intel.com> <20181114224921.12123-3-keith.busch@intel.com> <91369e94-d389-7cb9-6274-f46c9ec779d3@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <91369e94-d389-7cb9-6274-f46c9ec779d3@arm.com> User-Agent: Mutt/1.9.1 (2017-09-22) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 19, 2018 at 09:05:07AM +0530, Anshuman Khandual wrote: > On 11/15/2018 04:19 AM, Keith Busch wrote: > > Heterogeneous memory systems provide memory nodes with latency > > and bandwidth performance attributes that are different from other > > nodes. Create an interface for the kernel to register these attributes > > There are other properties like power consumption, reliability which can > be associated with a particular PA range. Also the set of properties has > to be extensible for the future. Sure, I'm just starting with the attributes available from HMAT, If there are additional possible attributes that make sense to add, I don't see why we can't continue appending them if this patch is okay. > > under the node that provides the memory. If the system provides this > > information, applications can query the node attributes when deciding > > which node to request memory. > > Right but each (memory initiator, memory target) should have these above > mentioned properties enumerated to have an 'property as seen' from kind > of semantics. > > > > > When multiple memory initiators exist, accessing the same memory target > > from each may not perform the same as the other. The highest performing > > initiator to a given target is considered to be a local initiator for > > that target. The kernel provides performance attributes only for the > > local initiators. > > As mentioned above the interface must enumerate a future extensible set > of properties for each (memory initiator, memory target) pair available > on the system. That seems less friendly to use if forces the application to figure out which CPU is the best for a given memory node rather than just provide that answer directly. > > The memory's compute node should be symlinked in sysfs as one of the > > node's initiators. > > Right. IIUC the first patch skips the linking process of for two nodes A > and B if (A == B) preventing association to local memory initiator. Right, CPUs and memory sharing a proximity domain are assumed to be local to each other, so not going to set up those links to itself.