From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751572AbcGLTh0 (ORCPT ); Tue, 12 Jul 2016 15:37:26 -0400 Received: from mx.treblig.org ([80.68.94.177]:34555 "EHLO mx.treblig.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750897AbcGLThY (ORCPT ); Tue, 12 Jul 2016 15:37:24 -0400 X-Greylist: delayed 1563 seconds by postgrey-1.27 at vger.kernel.org; Tue, 12 Jul 2016 15:37:24 EDT Date: Tue, 12 Jul 2016 20:10:49 +0100 From: "Dr. David Alan Gilbert" To: Peter Zijlstra Cc: "H. Peter Anvin" , paulmck@linux.vnet.ibm.com, tglx@linutronix.de, mingo@elte.hu, ak@linux.intel.com, linux-kernel@vger.kernel.org Subject: Re: [CRM114spam]: Re: Odd performance results Message-ID: <20160712191049.GB27918@gallifrey> References: <20160710042639.GA4068@linux.vnet.ibm.com> <7DF218CD-22F6-4E46-A628-2138AEA3A161@infradead.org> <20160710144327.GX4650@linux.vnet.ibm.com> <20160712145551.GU30909@twins.programming.kicks-ass.net> <20160712150529.GN7094@linux.vnet.ibm.com> <27d2c710-479d-77a9-f2c6-875e9c2bc40f@zytor.com> <20160712185120.GX30909@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160712185120.GX30909@twins.programming.kicks-ass.net> X-Chocolate: 70 percent or better cocoa solids preferably X-Operating-System: Linux/3.4.108-kvm-i386-20150619 (i686) X-Uptime: 20:08:21 up 48 days, 4:31, 1 user, load average: 0.03, 0.03, 0.05 User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Peter Zijlstra (peterz@infradead.org) wrote: > On Tue, Jul 12, 2016 at 10:49:58AM -0700, H. Peter Anvin wrote: > > On 07/12/16 08:05, Paul E. McKenney wrote: > > The CPU in question (and /proc/cpuinfo should show this) has four cores > > with a total of eight threads. The "siblings" and "cpu cores" fields in > > /proc/cpuinfo should show the same thing. So I am utterly confused > > about what is unexpected here? > > Typically threads are enumerated differently on Intel parts. Namely: > > cpu_id = code_id + nr_cores * smt_id > > which gives, for a 4 core, 2 thread part: > > 0-3: core 0-3, smt0 > 4-7: core 0-3, smt1 > > My Core i7-2600k for example has: > > $ cat /sys/devices/system/cpu/cpu*/topology/thread_siblings_list > 0,4 > 1,5 > 2,6 > 3,7 > 0,4 > 1,5 > 2,6 > 3,7 > > The ordering Paul has, namely 0,1 for core0,smt{0,1} is not something > I've ever seen on an Intel part. AMD otoh does enumerate their CMT stuff > like what Paul has. Paul's isn't unique: cat /sys/devices/system/cpu/cpu*/topology/thread_siblings_list 0-1 0-1 2-3 2-3 i7-3520M CPU @ 2.90GHz (Dual core with hyperthread, Thinkpad t530, fedora 24) Dave -- -----Open up your eyes, open up your mind, open up your code ------- / Dr. David Alan Gilbert | Running GNU/Linux | Happy \ \ dave @ treblig.org | | In Hex / \ _________________________|_____ http://www.treblig.org |_______/