From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH v6 05/11] pvqspinlock, x86: Allow unfair spinlock in a PV guest Date: Tue, 18 Mar 2014 09:14:45 +0100 Message-ID: <53280075.1020804@redhat.com> References: <1394650498-30118-1-git-send-email-Waiman.Long@hp.com> <1394650498-30118-6-git-send-email-Waiman.Long@hp.com> <53218E7A.8090707@citrix.com> <5321AF96.6070909@redhat.com> <20140317190511.GB11707@phenom.dumpdata.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20140317190511.GB11707@phenom.dumpdata.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: Konrad Rzeszutek Wilk Cc: Jeremy Fitzhardinge , Raghavendra K T , kvm@vger.kernel.org, Peter Zijlstra , virtualization@lists.linux-foundation.org, Andi Kleen , "H. Peter Anvin" , Michel Lespinasse , Alok Kataria , linux-arch@vger.kernel.org, Gleb Natapov , x86@kernel.org, Ingo Molnar , xen-devel@lists.xenproject.org, "Paul E. McKenney" , Rik van Riel , Arnd Bergmann , Scott J Norton , Steven Rostedt , Chris Wright , Thomas Gleixner , Aswin Chandramouleeswaran , Chegu Vinod , Waiman Long , Oleg Nesterov List-Id: linux-arch.vger.kernel.org Il 17/03/2014 20:05, Konrad Rzeszutek Wilk ha scritto: >> > Measurements were done by Gleb for two guests running 2.6.32 with 16 >> > vcpus each, on a 16-core system. One guest ran with unfair locks, >> > one guest ran with fair locks. Two kernel compilations ("time make > And when you say fair locks are you saying PV ticketlocks or generic > ticketlocks? Generic, of course. > You should see the same values with the PV ticketlock. It is not clear > to me if this testing did include that variant of locks? Yes, PV is fine. But up to this point of the series, we are concerned about spinlock performance when running on an overcommitted hypervisor that doesn't support PV spinlocks. Paolo From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ee0-f53.google.com ([74.125.83.53]:62418 "EHLO mail-ee0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751706AbaCRIO7 (ORCPT ); Tue, 18 Mar 2014 04:14:59 -0400 Message-ID: <53280075.1020804@redhat.com> Date: Tue, 18 Mar 2014 09:14:45 +0100 From: Paolo Bonzini MIME-Version: 1.0 Subject: Re: [PATCH v6 05/11] pvqspinlock, x86: Allow unfair spinlock in a PV guest References: <1394650498-30118-1-git-send-email-Waiman.Long@hp.com> <1394650498-30118-6-git-send-email-Waiman.Long@hp.com> <53218E7A.8090707@citrix.com> <5321AF96.6070909@redhat.com> <20140317190511.GB11707@phenom.dumpdata.com> In-Reply-To: <20140317190511.GB11707@phenom.dumpdata.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-arch-owner@vger.kernel.org List-ID: To: Konrad Rzeszutek Wilk Cc: Jeremy Fitzhardinge , Raghavendra K T , Gleb Natapov , Peter Zijlstra , virtualization@lists.linux-foundation.org, Andi Kleen , "H. Peter Anvin" , Michel Lespinasse , Alok Kataria , linux-arch@vger.kernel.org, kvm@vger.kernel.org, x86@kernel.org, Ingo Molnar , xen-devel@lists.xenproject.org, "Paul E. McKenney" , Rik van Riel , Arnd Bergmann , Scott J Norton , Steven Rostedt , Chris Wright , Thomas Gleixner , Aswin Chandramouleeswaran , Chegu Vinod , Waiman Long , Oleg Nesterov Message-ID: <20140318081445.D2JGb2eAhQ8USTeNlTVVSns_eJRBrrmNegvTKpmNdHc@z> Il 17/03/2014 20:05, Konrad Rzeszutek Wilk ha scritto: >> > Measurements were done by Gleb for two guests running 2.6.32 with 16 >> > vcpus each, on a 16-core system. One guest ran with unfair locks, >> > one guest ran with fair locks. Two kernel compilations ("time make > And when you say fair locks are you saying PV ticketlocks or generic > ticketlocks? Generic, of course. > You should see the same values with the PV ticketlock. It is not clear > to me if this testing did include that variant of locks? Yes, PV is fine. But up to this point of the series, we are concerned about spinlock performance when running on an overcommitted hypervisor that doesn't support PV spinlocks. Paolo