From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1422824AbcFMMX4 (ORCPT ); Mon, 13 Jun 2016 08:23:56 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:24221 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1422788AbcFMMXy (ORCPT ); Mon, 13 Jun 2016 08:23:54 -0400 X-IBM-Helo: d06dlp01.portsmouth.uk.ibm.com X-IBM-MailFrom: heiko.carstens@de.ibm.com X-IBM-RcptTo: linux-kernel@vger.kernel.org Date: Mon, 13 Jun 2016 13:22:30 +0200 From: Heiko Carstens To: Peter Zijlstra Cc: Greg Kroah-Hartman , Martin Schwidefsky , linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] s390/topology: add drawer scheduling domain level References: <1465376956-100711-1-git-send-email-heiko.carstens@de.ibm.com> <1465376956-100711-3-git-send-email-heiko.carstens@de.ibm.com> <20160613110621.GV30909@twins.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160613110621.GV30909@twins.programming.kicks-ass.net> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16061312-0016-0000-0000-000001F70219 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16061311-0017-0000-0000-000021E3FC18 Message-Id: <20160613112230.GA3808@osiris> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-06-13_06:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 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-1606130140 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 13, 2016 at 01:06:21PM +0200, Peter Zijlstra wrote: > On Wed, Jun 08, 2016 at 11:09:16AM +0200, Heiko Carstens wrote: > > The z13 machine added a fourth level to the cpu topology > > information. The new top level is called drawer. > > > > A drawer contains two books, which used to be the top level. > > > > Adding this additional scheduling domain did show performance > > improvements for some workloads of up to 8%, while there don't > > seem to be any workloads impacted in a negative way. > > Right; so no objection. > > Acked-by: Peter Zijlstra (Intel) Thanks! > You still don't want to make NUMA explicit on this thing? So while I > suppose the SC 480M L4 cache does hide some of it, there can be up to 8 > nodes on this thing. Which seems to me there's win to be had by exposing > it. > > Of course, the moment you go all virt/LPAR on it, that all gets really > interesting, but for those cases where you run 1:1 it might make sense. Yes, and actually we are all virt/LPAR always, so this is unfortunately not very easy to do. And yes, I do agree that for the 1:1 case it most likely would make sense, however we don't have any run-time guarantee to stay 1:1. > Also, are you sure you don't want some of the behaviour changed for the > drawer domains? I could for example imagine you wouldn't want > SD_WAKE_AFFINE set (we disable that for NUMA domains as well). That's something we need to look into further as well. Thanks for pointing this out!