From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750862AbcGJE0a (ORCPT ); Sun, 10 Jul 2016 00:26:30 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:29231 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750721AbcGJE03 (ORCPT ); Sun, 10 Jul 2016 00:26:29 -0400 X-IBM-Helo: d03dlp01.boulder.ibm.com X-IBM-MailFrom: paulmck@linux.vnet.ibm.com Date: Sat, 9 Jul 2016 21:26:39 -0700 From: "Paul E. McKenney" To: peterz@infradead.org, hpa@zytor.com, tglx@linutronix.de, mingo@elte.hu, ak@linux.intel.com Cc: linux-kernel@vger.kernel.org Subject: Odd performance results Reply-To: paulmck@linux.vnet.ibm.com MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16071004-0016-0000-0000-0000042555E0 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16071004-0017-0000-0000-000030F82394 Message-Id: <20160710042639.GA4068@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-07-09_11:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=80 spamscore=80 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1604210000 definitions=main-1607100054 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello! So I ran a quick benchmark which showed stair-step results. I immediately thought "Ah, this is due to CPU 0 and 1, 2 and 3, 4 and 5, and 6 and 7 being threads in a core." Then I thought "Wait, this is an x86!" Then I dumped out cpu*/topology/thread_siblings_list, getting the following: cpu0/topology/thread_siblings_list: 0-1 cpu1/topology/thread_siblings_list: 0-1 cpu2/topology/thread_siblings_list: 2-3 cpu3/topology/thread_siblings_list: 2-3 cpu4/topology/thread_siblings_list: 4-5 cpu5/topology/thread_siblings_list: 4-5 cpu6/topology/thread_siblings_list: 6-7 cpu7/topology/thread_siblings_list: 6-7 Is this now expected behavior or a fluke of my particular laptop? Here is hoping for expected behavior, as it makes NUMA locality the default for a great many workloads. Enlightenment? Thanx, Paul