Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756949Ab2EGOrx (ORCPT ); Mon, 7 May 2012 10:47:53 -0400 Received: from e23smtp02.au.ibm.com ([202.81.31.144]:37984 "EHLO e23smtp02.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756467Ab2EGOrv (ORCPT ); Mon, 7 May 2012 10:47:51 -0400 Message-ID: <4FA7E06E.20304@linux.vnet.ibm.com> Date: Mon, 07 May 2012 20:17:10 +0530 From: Raghavendra K T Organization: IBM User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.1) Gecko/20120216 Thunderbird/10.0.1 MIME-Version: 1.0 To: Avi Kivity CC: Srivatsa Vaddagiri , Ingo Molnar , Linus Torvalds , Andrew Morton , Jeremy Fitzhardinge , Greg Kroah-Hartman , Konrad Rzeszutek Wilk , "H. Peter Anvin" , Marcelo Tosatti , X86 , Gleb Natapov , Ingo Molnar , Attilio Rao , Virtualization , Xen Devel , linux-doc@vger.kernel.org, KVM , Andi Kleen , Stefano Stabellini , Stephan Diestelhorst , LKML , Peter Zijlstra , Thomas Gleixner Subject: Re: [PATCH RFC V8 0/17] Paravirtualized ticket spinlocks References: <20120502100610.13206.40.sendpatchset@codeblue.in.ibm.com> <20120507082928.GI16608@gmail.com> <4FA7888F.80505@redhat.com> <4FA7AAD8.6050003@linux.vnet.ibm.com> <4FA7BABA.4040700@redhat.com> <4FA7CC05.50808@linux.vnet.ibm.com> <4FA7CCA2.4030408@redhat.com> <4FA7D06B.60005@linux.vnet.ibm.com> <20120507134611.GB5533@linux.vnet.ibm.com> <4FA7D2E5.1020607@redhat.com> <4FA7D3F7.9080005@linux.vnet.ibm.com> <4FA7D50D.1020209@redhat.com> In-Reply-To: <4FA7D50D.1020209@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit x-cbid: 12050704-5490-0000-0000-0000014C851D Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1382 Lines: 34 On 05/07/2012 07:28 PM, Avi Kivity wrote: > On 05/07/2012 04:53 PM, Raghavendra K T wrote: >>> Is the improvement so low, because PLE is interfering with the patch, or >>> because PLE already does a good job? >>> >> >> >> It is because PLE already does a good job (of not burning cpu). The >> 1-3% improvement is because, patchset knows atleast who is next to hold >> lock, which is lacking in PLE. >> > > Not good. Solving a problem in software that is already solved by > hardware? It's okay if there are no costs involved, but here we're > introducing a new ABI that we'll have to maintain for a long time. > Hmm agree that being a step ahead of mighty hardware (and just an improvement of 1-3%) is no good for long term (where PLE is future). Having said that, it is hard for me to resist saying : bottleneck is somewhere else on PLE m/c and IMHO answer would be combination of paravirt-spinlock + pv-flush-tb. But I need to come up with good number to argue in favour of the claim. PS: Nikunj had experimented that pv-flush tlb + paravirt-spinlock is a win on PLE where only one of them alone could not prove the benefit. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/