From mboxrd@z Thu Jan 1 00:00:00 1970 From: Waiman Long Subject: Re: [PATCH v6 05/11] pvqspinlock, x86: Allow unfair spinlock in a PV guest Date: Tue, 18 Mar 2014 23:15:25 -0400 Message-ID: <53290BCD.8010001@hp.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> <53280075.1020804@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from g6t1524.atlanta.hp.com ([15.193.200.67]:19432 "EHLO g6t1524.atlanta.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932755AbaCSDPd (ORCPT ); Tue, 18 Mar 2014 23:15:33 -0400 In-Reply-To: <53280075.1020804@redhat.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Paolo Bonzini Cc: Konrad Rzeszutek Wilk , 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 , Oleg On 03/18/2014 04:14 AM, Paolo Bonzini wrote: > 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. The unfair queue lock is designed in such a way that it will only be activated when running in a PV guest or it won't be mergeable upstream. So there must be some way to determine if it is running under a hypervisor. -Longman From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from g6t1524.atlanta.hp.com ([15.193.200.67]:19432 "EHLO g6t1524.atlanta.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932755AbaCSDPd (ORCPT ); Tue, 18 Mar 2014 23:15:33 -0400 Message-ID: <53290BCD.8010001@hp.com> Date: Tue, 18 Mar 2014 23:15:25 -0400 From: Waiman Long 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> <53280075.1020804@redhat.com> In-Reply-To: <53280075.1020804@redhat.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: Paolo Bonzini Cc: Konrad Rzeszutek Wilk , 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 , Oleg Nesterov Message-ID: <20140319031525.DRV6CXuFoxK6OTs1gbcs5j0V_d7W4-Xpfxr-0hL91Fg@z> On 03/18/2014 04:14 AM, Paolo Bonzini wrote: > 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. The unfair queue lock is designed in such a way that it will only be activated when running in a PV guest or it won't be mergeable upstream. So there must be some way to determine if it is running under a hypervisor. -Longman