From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753788Ab2I0MHM (ORCPT ); Thu, 27 Sep 2012 08:07:12 -0400 Received: from mx1.redhat.com ([209.132.183.28]:2315 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751140Ab2I0MHK (ORCPT ); Thu, 27 Sep 2012 08:07:10 -0400 Message-ID: <50644148.5090201@redhat.com> Date: Thu, 27 Sep 2012 14:06:32 +0200 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:15.0) Gecko/20120828 Thunderbird/15.0 MIME-Version: 1.0 To: Raghavendra K T CC: Jiannan Ouyang , Peter Zijlstra , Rik van Riel , "H. Peter Anvin" , Ingo Molnar , Marcelo Tosatti , Srikar , "Nikunj A. Dadhania" , KVM , chegu vinod , "Andrew M. Theurer" , LKML , Srivatsa Vaddagiri , Gleb Natapov Subject: Re: [PATCH RFC 1/2] kvm: Handle undercommitted guest case in PLE handler References: <20120921115942.27611.67488.sendpatchset@codeblue> <20120921120000.27611.71321.sendpatchset@codeblue> <505C654B.2050106@redhat.com> <505CA2EB.7050403@linux.vnet.ibm.com> <50607F1F.2040704@redhat.com> <5060851E.1030404@redhat.com> <506166B4.4010207@linux.vnet.ibm.com> <5061713D.5060406@redhat.com> <50641356.5070008@redhat.com> <50643802.5050200@linux.vnet.ibm.com> In-Reply-To: <50643802.5050200@linux.vnet.ibm.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/27/2012 01:26 PM, Raghavendra K T wrote: > On 09/27/2012 02:20 PM, Avi Kivity wrote: >> On 09/25/2012 04:43 PM, Jiannan Ouyang wrote: >>> I've actually implemented this preempted_bitmap idea. >> >> Interesting, please share the code if you can. >> >>> However, I'm doing this to expose this information to the guest, so the >>> guest is able to know if the lock holder is preempted or not before >>> spining. Right now, I'm doing experiment to show that this idea works. >>> >>> I'm wondering what do you guys think of the relationship between the >>> pv_ticketlock approach and PLE handler approach. Are we going to adopt >>> PLE instead of the pv ticketlock, and why? >> >> Right now we're searching for the best solution. The tradeoffs are more >> or less: >> >> PLE: >> - works for unmodified / non-Linux guests >> - works for all types of spins (e.g. smp_call_function*()) >> - utilizes an existing hardware interface (PAUSE instruction) so likely >> more robust compared to a software interface >> >> PV: >> - has more information, so it can perform better > > Should we also consider that we always have an edge here for non-PLE > machine? True. The deployment share for these is decreasing rapidly though. I hate optimizing for obsolete hardware. -- error compiling committee.c: too many arguments to function