From mboxrd@z Thu Jan 1 00:00:00 1970 From: Raghavendra K T Subject: Re: [PATCH v8 00/10] qspinlock: a 4-byte queue spinlock with PV support Date: Mon, 07 Apr 2014 23:21:46 +0530 Message-ID: <5342E5B2.1070306@linux.vnet.ibm.com> References: <1396445259-27670-1-git-send-email-Waiman.Long@hp.com> <5342425A.7040005@linux.vnet.ibm.com> <5342D475.7060503@hp.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5342D475.7060503@hp.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: Waiman Long Cc: linux-arch@vger.kernel.org, Rik van Riel , Gleb Natapov , kvm@vger.kernel.org, Konrad Rzeszutek Wilk , Peter Zijlstra , Scott J Norton , x86@kernel.org, Paolo Bonzini , linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Ingo Molnar , Chegu Vinod , David Vrabel , "H. Peter Anvin" , xen-devel@lists.xenproject.org, Thomas Gleixner , "Paul E. McKenney" , Linus Torvalds , Oleg Nesterov , Aswin Chandramouleeswaran List-Id: linux-arch.vger.kernel.org On 04/07/2014 10:08 PM, Waiman Long wrote: > On 04/07/2014 02:14 AM, Raghavendra K T wrote: [...] >> But I am seeing hang in overcommit cases. Gdb showed that many vcpus >> are halted and there was no progress. Suspecting the problem /race with >> halting, I removed the halt() part of kvm_hibernate(). I am yet to >> take a closer look at the code on halt() related changes. > > It seems like there may still be race conditions where the current code > is not handling correctly. I will look into that to see where the > problem is. BTW, what test do you use to produce the hang condition? Running ebizzy on 2 of the vms simultaneously (for sometime in repeated loop) could reproduce it. >> Patch series with that change gave around 20% improvement for dbench >> 2x and 30% improvement for ebizzy 2x cases. (1x has no significant >> loss/gain). >> While at it, Just a correction it was 30% for ebizzy1.5x and around 80% for ebizzy 2x. > What is the baseline for the performance improvement? Is it without the > unfair lock and PV qspinlock? Baseline was 3.14-rc8 without any of the qspin patch series. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e23smtp02.au.ibm.com ([202.81.31.144]:52222 "EHLO e23smtp02.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755610AbaDGRqt (ORCPT ); Mon, 7 Apr 2014 13:46:49 -0400 Received: from /spool/local by e23smtp02.au.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 8 Apr 2014 03:46:46 +1000 Message-ID: <5342E5B2.1070306@linux.vnet.ibm.com> Date: Mon, 07 Apr 2014 23:21:46 +0530 From: Raghavendra K T MIME-Version: 1.0 Subject: Re: [PATCH v8 00/10] qspinlock: a 4-byte queue spinlock with PV support References: <1396445259-27670-1-git-send-email-Waiman.Long@hp.com> <5342425A.7040005@linux.vnet.ibm.com> <5342D475.7060503@hp.com> In-Reply-To: <5342D475.7060503@hp.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: Waiman Long Cc: Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , Peter Zijlstra , linux-arch@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, xen-devel@lists.xenproject.org, kvm@vger.kernel.org, Paolo Bonzini , Konrad Rzeszutek Wilk , "Paul E. McKenney" , Rik van Riel , Linus Torvalds , David Vrabel , Oleg Nesterov , Gleb Natapov , Aswin Chandramouleeswaran , Scott J Norton , Chegu Vinod Message-ID: <20140407175146.QcXzca1tFRpftEws08iuRzi7GW6zUyQpBiVm0l3L_hQ@z> On 04/07/2014 10:08 PM, Waiman Long wrote: > On 04/07/2014 02:14 AM, Raghavendra K T wrote: [...] >> But I am seeing hang in overcommit cases. Gdb showed that many vcpus >> are halted and there was no progress. Suspecting the problem /race with >> halting, I removed the halt() part of kvm_hibernate(). I am yet to >> take a closer look at the code on halt() related changes. > > It seems like there may still be race conditions where the current code > is not handling correctly. I will look into that to see where the > problem is. BTW, what test do you use to produce the hang condition? Running ebizzy on 2 of the vms simultaneously (for sometime in repeated loop) could reproduce it. >> Patch series with that change gave around 20% improvement for dbench >> 2x and 30% improvement for ebizzy 2x cases. (1x has no significant >> loss/gain). >> While at it, Just a correction it was 30% for ebizzy1.5x and around 80% for ebizzy 2x. > What is the baseline for the performance improvement? Is it without the > unfair lock and PV qspinlock? Baseline was 3.14-rc8 without any of the qspin patch series.