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_HELO_NONE,SPF_PASS,URIBL_BLOCKED,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 D75C6C04AB6 for ; Fri, 31 May 2019 09:37:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B4F72266FC for ; Fri, 31 May 2019 09:37:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726911AbfEaJhw (ORCPT ); Fri, 31 May 2019 05:37:52 -0400 Received: from foss.arm.com ([217.140.101.70]:48884 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726280AbfEaJhv (ORCPT ); Fri, 31 May 2019 05:37:51 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 735ED341; Fri, 31 May 2019 02:37:50 -0700 (PDT) Received: from e107155-lin (e107155-lin.cambridge.arm.com [10.1.196.42]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 106B93F59C; Fri, 31 May 2019 02:37:45 -0700 (PDT) Date: Fri, 31 May 2019 10:37:43 +0100 From: Sudeep Holla To: Russell King - ARM Linux admin Cc: Morten Rasmussen , "Andrew F. Davis" , Atish Patra , linux-kernel@vger.kernel.org, Rob Herring , Albert Ou , Anup Patel , Catalin Marinas , "David S. Miller" , devicetree@vger.kernel.org, Greg Kroah-Hartman , Ingo Molnar , Jeremy Linton , Linus Walleij , linux-riscv@lists.infradead.org, Mark Rutland , Mauro Carvalho Chehab , Otto Sabart , Palmer Dabbelt , Paul Walmsley , "Peter Zijlstra (Intel)" , "Rafael J. Wysocki" , Rob Herring , Thomas Gleixner , Will Deacon , Sudeep Holla , linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v6 1/7] Documentation: DT: arm: add support for sockets defining package boundaries Message-ID: <20190531093743.GB18292@e107155-lin> References: <20190529211340.17087-1-atish.patra@wdc.com> <20190529211340.17087-2-atish.patra@wdc.com> <49f41e62-5354-a674-d95f-5f63851a0ca6@ti.com> <20190530115103.GA10919@e105550-lin.cambridge.arm.com> <20190530214254.tuxsnyv52a2fyhck@shell.armlinux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190530214254.tuxsnyv52a2fyhck@shell.armlinux.org.uk> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 30, 2019 at 10:42:54PM +0100, Russell King - ARM Linux admin wrote: > On Thu, May 30, 2019 at 12:51:03PM +0100, Morten Rasmussen wrote: > > On Wed, May 29, 2019 at 07:39:17PM -0400, Andrew F. Davis wrote: > > > On 5/29/19 5:13 PM, Atish Patra wrote: > > > >From: Sudeep Holla > > > > > > > >The current ARM DT topology description provides the operating system > > > >with a topological view of the system that is based on leaf nodes > > > >representing either cores or threads (in an SMT system) and a > > > >hierarchical set of cluster nodes that creates a hierarchical topology > > > >view of how those cores and threads are grouped. > > > > > > > >However this hierarchical representation of clusters does not allow to > > > >describe what topology level actually represents the physical package or > > > >the socket boundary, which is a key piece of information to be used by > > > >an operating system to optimize resource allocation and scheduling. > > > > > > > > > > Are physical package descriptions really needed? What does "socket" imply > > > that a higher layer "cluster" node grouping does not? It doesn't imply a > > > different NUMA distance and the definition of "socket" is already not well > > > defined, is a dual chiplet processor not just a fancy dual "socket" or are > > > dual "sockets" on a server board "slotket" card, will we need new names for > > > those too.. > > > > Socket (or package) just implies what you suggest, a grouping of CPUs > > based on the physical socket (or package). Some resources might be > > associated with packages and more importantly socket information is > > exposed to user-space. At the moment clusters are being exposed to > > user-space as sockets which is less than ideal for some topologies. > > Please point out a 32-bit ARM system that has multiple "socket"s. > > As far as I'm aware, all 32-bit systems do not have socketed CPUs > (modern ARM CPUs are part of a larger SoC), and the CPUs are always > in one package. > > Even the test systems I've seen do not have socketed CPUs. > As far as we know, there's none. So we simply have to assume all those systems are single socket(IOW all CPUs reside inside a single SoC package) system. -- Regards, Sudeep