From mboxrd@z Thu Jan 1 00:00:00 1970 Received: by 10.25.159.19 with SMTP id i19csp974293lfe; Fri, 5 Feb 2016 03:01:12 -0800 (PST) X-Received: by 10.55.75.144 with SMTP id y138mr15541719qka.96.1454670072203; Fri, 05 Feb 2016 03:01:12 -0800 (PST) Return-Path: Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu. [128.59.11.253]) by mx.google.com with ESMTP id 1si15342855qkv.22.2016.02.05.03.01.11; Fri, 05 Feb 2016 03:01:12 -0800 (PST) Received-SPF: pass (google.com: domain of kvmarm-bounces@lists.cs.columbia.edu designates 128.59.11.253 as permitted sender) client-ip=128.59.11.253; Authentication-Results: mx.google.com; spf=pass (google.com: domain of kvmarm-bounces@lists.cs.columbia.edu designates 128.59.11.253 as permitted sender) smtp.mailfrom=kvmarm-bounces@lists.cs.columbia.edu Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id BC7AE495BD; Fri, 5 Feb 2016 05:55:38 -0500 (EST) X-Virus-Scanned: at lists.cs.columbia.edu X-Spam-Flag: NO X-Spam-Score: -4.201 X-Spam-Level: X-Spam-Status: No, score=-4.201 required=6.1 tests=[BAYES_00=-1.9, DNS_FROM_AHBL_RHSBL=2.699, RCVD_IN_DNSWL_HI=-5] autolearn=unavailable Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id C1jkhdMhiFpH; Fri, 5 Feb 2016 05:55:36 -0500 (EST) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 968CA49616; Fri, 5 Feb 2016 05:55:36 -0500 (EST) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 1B45449616 for ; Fri, 5 Feb 2016 05:55:35 -0500 (EST) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id x5TSybEtRNxU for ; Fri, 5 Feb 2016 05:55:32 -0500 (EST) Received: from foss.arm.com (foss.arm.com [217.140.101.70]) by mm01.cs.columbia.edu (Postfix) with ESMTP id B3C99495BD for ; Fri, 5 Feb 2016 05:55:32 -0500 (EST) 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 2B4843A1; Fri, 5 Feb 2016 03:00:19 -0800 (PST) Received: from leverpostej (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 40A823F213; Fri, 5 Feb 2016 03:01:03 -0800 (PST) Date: Fri, 5 Feb 2016 11:00:33 +0000 From: Mark Rutland To: Andrew Jones Subject: Re: MPIDR Aff0 question Message-ID: <20160205110032.GA19614@leverpostej> References: <20160204183801.GF3890@hawk.localdomain> <56B39D9A.7000008@arm.com> <20160205092353.GA3873@hawk.localdomain> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20160205092353.GA3873@hawk.localdomain> User-Agent: Mutt/1.5.21 (2010-09-15) Cc: Marc Zyngier , andre.przywara@arm.com, qemu-arm@nongnu.org, kvmarm@lists.cs.columbia.edu X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu X-TUID: ZaUbNnDaJ+kz On Fri, Feb 05, 2016 at 10:23:53AM +0100, Andrew Jones wrote: > On Thu, Feb 04, 2016 at 06:51:06PM +0000, Marc Zyngier wrote: > What would the benefit of defining a "socket"? > > That's a good lead in for my next question. While I don't believe > there needs to be any relationship between socket and numa node, I > suspect on real machines there is, and quite possibly socket == node. > Shannon is adding numa support to QEMU right now. Without special > configuration there's no gain other than illusion, but with pinning, > etc. the guest numa nodes will map to host nodes, and thus passing > that information on to the guest's kernel is useful. Populating a > socket/node affinity field seems to me like a needed step. But, > question time, is it? Maybe not. I don't think it's necessary. When using ACPI, NUMA info comes from SRAT+SLIT, and the MPIDR.Aff* fields do not provide NUMA topology info. I expect the same to be true with DT using something like numa-distance-map [1]. > Also, the way Linux currently handles non-thread using MPIDRs > (Aff1:socket, Aff0:core) throws a wrench at the Aff2:socket, > Aff1:"cluster", Aff0:core(max 16) plan. Either the plan or Linux > would need to be changed. The topology can be explicitly overridden in DT using cpu-map [2]. I don't know what the story for ACPI is. Mark. [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2016-February/404057.html [2] https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/arm/topology.txt?h=v4.5-rc2&id=36f90b0a2ddd60823fe193a85e60ff1906c2a9b3 _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm