From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753637AbcHQFrl (ORCPT ); Wed, 17 Aug 2016 01:47:41 -0400 Received: from mx2.suse.de ([195.135.220.15]:35242 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750784AbcHQFqo (ORCPT ); Wed, 17 Aug 2016 01:46:44 -0400 Date: Wed, 17 Aug 2016 07:46:05 +0200 From: Borislav Petkov To: "H. Peter Anvin" Cc: kernel test robot , Ville =?utf-8?B?U3lyasOkbMOk?= , Linus Torvalds , Andy Lutomirski , Brian Gerst , Denys Vlasenko , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , LKML , lkp@01.org Subject: Re: [lkp] [x86/hweight] 65ea11ec6a: will-it-scale.per_process_ops 9.3% improvement Message-ID: <20160817054605.GA6728@nazgul.tnic> References: <20160816142642.GA24206@yexl-desktop> <9FF32F53-5EF8-40D4-B696-A30FDF7201E1@zytor.com> <20160816171635.GA10542@nazgul.tnic> <796A2A72-06B7-4B3D-AA38-DF558FC75857@zytor.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <796A2A72-06B7-4B3D-AA38-DF558FC75857@zytor.com> User-Agent: Mutt/1.6.0 (2016-04-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 16, 2016 at 04:09:19PM -0700, H. Peter Anvin wrote: > On August 16, 2016 10:16:35 AM PDT, Borislav Petkov wrote: > >On Tue, Aug 16, 2016 at 09:59:00AM -0700, H. Peter Anvin wrote: > >> Dang... > > > >Isn't 9.3% improvement a good thing(tm) ? > > Yes, it's huge. The only explanation I could imagine is that scrambling %rdi caused the scheduler to do completely the wrong thing. I'm questioning the validity, actually. Report says test machine was Sandy Bridge-EP and I'd bet good money this one has POPCNT support so how are we even hitting that __sw_hweight64() path, at all? -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) -- From mboxrd@z Thu Jan 1 00:00:00 1970 Content-Type: multipart/mixed; boundary="===============6519838713614670770==" MIME-Version: 1.0 From: Borislav Petkov To: lkp@lists.01.org Subject: Re: [x86/hweight] 65ea11ec6a: will-it-scale.per_process_ops 9.3% improvement Date: Wed, 17 Aug 2016 07:46:05 +0200 Message-ID: <20160817054605.GA6728@nazgul.tnic> In-Reply-To: <796A2A72-06B7-4B3D-AA38-DF558FC75857@zytor.com> List-Id: --===============6519838713614670770== Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable On Tue, Aug 16, 2016 at 04:09:19PM -0700, H. Peter Anvin wrote: > On August 16, 2016 10:16:35 AM PDT, Borislav Petkov wrote: > >On Tue, Aug 16, 2016 at 09:59:00AM -0700, H. Peter Anvin wrote: > >> Dang... > > > >Isn't 9.3% improvement a good thing(tm) ? > = > Yes, it's huge. The only explanation I could imagine is that scrambling = %rdi caused the scheduler to do completely the wrong thing. I'm questioning the validity, actually. Report says test machine was Sandy Bridge-EP and I'd bet good money this one has POPCNT support so how are we even hitting that __sw_hweight64() path, at all? -- = Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. SUSE Linux GmbH, GF: Felix Imend=C3=B6rffer, Jane Smithard, Graham Norton, = HRB 21284 (AG N=C3=BCrnberg) -- --===============6519838713614670770==--