From mboxrd@z Thu Jan 1 00:00:00 1970 From: Raghavendra K T Subject: Re: [PATCH RFC V9 0/19] Paravirtualized ticket spinlocks Date: Wed, 10 Jul 2013 16:58:29 +0530 Message-ID: <51DD455D.4000701@linux.vnet.ibm.com> References: <1372171802.3804.30.camel@oc2024037011.ibm.com> <51CAAA26.4090204@linux.vnet.ibm.com> <20130626113744.GA6300@hawk.usersys.redhat.com> <20130626125240.GY18508@redhat.com> <51CAEF45.3010203@linux.vnet.ibm.com> <20130626161130.GB18152@redhat.com> <51CB2AD9.5060508@linux.vnet.ibm.com> <51DBD3C2.2040807@linux.vnet.ibm.com> <20130710103325.GP24941@redhat.com> <20130710104047.GP25631@dyad.programming.kicks-ass.net> <20130710104717.GR24941@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20130710104717.GR24941@redhat.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: Gleb Natapov Cc: jeremy@goop.org, gregkh@suse.de, kvm@vger.kernel.org, linux-doc@vger.kernel.org, Peter Zijlstra , riel@redhat.com, virtualization@lists.linux-foundation.org, andi@firstfloor.org, hpa@zytor.com, stefano.stabellini@eu.citrix.com, xen-devel@lists.xensource.com, x86@kernel.org, mingo@redhat.com, habanero@linux.vnet.ibm.com, Andrew Jones , konrad.wilk@oracle.com, ouyang@cs.pitt.edu, avi.kivity@gmail.com, tglx@linutronix.de, chegu_vinod@hp.com, linux-kernel@vger.kernel.org, srivatsa.vaddagiri@gmail.com, attilio.rao@citrix.com, pbonzini@redhat.com, torvalds@linux-foundation.org, stephan.diestelhorst@amd.com List-Id: xen-devel@lists.xenproject.org On 07/10/2013 04:17 PM, Gleb Natapov wrote: > On Wed, Jul 10, 2013 at 12:40:47PM +0200, Peter Zijlstra wrote: >> On Wed, Jul 10, 2013 at 01:33:25PM +0300, Gleb Natapov wrote: >> >> Here's an idea, trim the damn email ;-) -- not only directed at gleb. >> > Good idea. > >>>> Ingo, Gleb, >>>> >>>> From the results perspective, Andrew Theurer, Vinod's test results are >>>> pro-pvspinlock. >>>> Could you please help me to know what will make it a mergeable >>>> candidate?. >>>> >>> I need to spend more time reviewing it :) The problem with PV interfaces >>> is that they are easy to add but hard to get rid of if better solution >>> (HW or otherwise) appears. >> >> How so? Just make sure the registration for the PV interface is optional; that >> is, allow it to fail. A guest that fails the PV setup will either have to try >> another PV interface or fall back to 'native'. >> > We have to carry PV around for live migration purposes. PV interface > cannot disappear under a running guest. > IIRC, The only requirement was running state of the vcpu to be retained. This was addressed by [PATCH RFC V10 13/18] kvm : Fold pv_unhalt flag into GET_MP_STATE ioctl to aid migration. I would have to know more if I missed something here. >>>> I agree that Jiannan's Preemptable Lock idea is promising and we could >>>> evaluate that approach, and make the best one get into kernel and also >>>> will carry on discussion with Jiannan to improve that patch. >>> That would be great. The work is stalled from what I can tell. >> >> I absolutely hated that stuff because it wrecked the native code. > Yes, the idea was to hide it from native code behind PV hooks. >