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=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, T_DKIMWL_WL_HIGH,URIBL_BLOCKED,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 2A118C28CC0 for ; Thu, 30 May 2019 13:13:03 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id F32442596B for ; Thu, 30 May 2019 13:13:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="S03sxHoA" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F32442596B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-riscv-bounces+infradead-linux-riscv=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=dTRMgfFVk+glSgw8b9L/0H7GfPsBtO9z9Up/LV4G/H0=; b=S03sxHoAHRpkH8 bFc7r4sF1hPwJOfJG3nrsvbl8bSiWnTRU7urJ1qzW+F7Te9WpOtnaDhYIfFuaJXOcL5wb3AnNGWBu 87l0bSY5hx2493uJFV1zRrIn5iic9rz1UNKiGDbpM2WSuTrHPmpWl4LVbD9lltyy/9cR9yhiD9/ma gC7p2HalxcIguc4owcxmCVocoTZkZnbbv2iSPZqCxHjR1Lhpivt4jiZxV049/6xiq1/XwbJbugzR3 mtiGLembZYkTpRhUr0yf+YGKIzqg3iSDbim4x3a/1OHHs+rkKaLI8ryew6XgwFKqP4VdRc9xeeMRJ glS8kCBq69mLruxT672g==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hWKrZ-0001qG-LW; Thu, 30 May 2019 13:12:57 +0000 Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70] helo=foss.arm.com) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hWKrS-0001jZ-8X; Thu, 30 May 2019 13:12:51 +0000 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 0E194A78; Thu, 30 May 2019 06:12:48 -0700 (PDT) Received: from e105550-lin.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id C29753F59C; Thu, 30 May 2019 06:12:43 -0700 (PDT) Date: Thu, 30 May 2019 14:12:41 +0100 From: Morten Rasmussen To: "Andrew F. Davis" Subject: Re: [PATCH v6 1/7] Documentation: DT: arm: add support for sockets defining package boundaries Message-ID: <20190530131241.GB10919@e105550-lin.cambridge.arm.com> 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> <70639181-09d1-4644-f062-b19e06db7471@ti.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <70639181-09d1-4644-f062-b19e06db7471@ti.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190530_061250_313796_DBC854D3 X-CRM114-Status: GOOD ( 24.84 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , "Rafael J. Wysocki" , "Peter Zijlstra \(Intel\)" , Catalin Marinas , Linus Walleij , Palmer Dabbelt , Will Deacon , Atish Patra , Mauro Carvalho Chehab , linux-riscv@lists.infradead.org, Ingo Molnar , Rob Herring , Anup Patel , Russell King , devicetree@vger.kernel.org, Albert Ou , Rob Herring , Paul Walmsley , Thomas Gleixner , linux-arm-kernel@lists.infradead.org, Greg Kroah-Hartman , linux-kernel@vger.kernel.org, Jeremy Linton , Otto Sabart , Sudeep Holla , "David S. Miller" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+infradead-linux-riscv=archiver.kernel.org@lists.infradead.org On Thu, May 30, 2019 at 08:56:03AM -0400, Andrew F. Davis wrote: > On 5/30/19 7:51 AM, 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. > > > > I see the benefit of reporting the physical layout and packaging information > to user-space for tracking reasons, but from software perspective this > doesn't matter, and the resource partitioning should be described elsewhere > (NUMA nodes being the go to example). That would make defining a NUMA node mandatory even for non-NUMA systems? > >At the moment user-space is only told about hw threads, cores, and > >sockets. In the very near future it is going to be told about dies too > >(look for Len Brown's multi-die patch set). > > > > Seems my hypothetical case is already in the works :( Indeed. IIUC, the reasoning behind it is related to actual multi-die x86 packages and some rapl stuff being per-die or per-core. > > >I don't see how we can provide correct information to user-space based > >on the current information in DT. I'm not convinced it was a good idea > >to expose this information to user-space to begin with but that is > >another discussion. > > > > Fair enough, it's a little late now to un-expose this info to userspace so > we should at least present it correctly. My worry was this getting out of > hand with layering, for instance what happens when we need to add die nodes > in-between cluster and socket? If we want the die mask to be correct for arm/arm64/riscv we need die information from somewhere. I'm not in favour of adding more topology layers to the user-space visible topology description, but others might have a valid reason and if it is exposed I would prefer if we try to expose the right information. Btw, for packages, we already have that information in ACPI/PPTT so it would be nice if we could have that for DT based systems too. Morten _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv