From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1752851Ab1AYB2w (ORCPT <rfc822;w@1wt.eu>);
	Mon, 24 Jan 2011 20:28:52 -0500
Received: from mx1.redhat.com ([209.132.183.28]:35697 "EHLO mx1.redhat.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1751532Ab1AYB2u (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Mon, 24 Jan 2011 20:28:50 -0500
Subject: Re: [PATCH 14/16] KVM-GST: KVM Steal time registration
From: Glauber Costa <glommer@redhat.com>
To: Rik van Riel <riel@redhat.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, aliguori@us.ibm.com,
        Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>,
        Peter Zijlstra <peterz@infradead.org>, Avi Kivity <avi@redhat.com>
In-Reply-To: <4D3E26E3.3000209@redhat.com>
References: <1295892397-11354-1-git-send-email-glommer@redhat.com>
	 <1295892397-11354-15-git-send-email-glommer@redhat.com>
	 <4D3E0BB9.5070805@redhat.com>
	 <1295918712.15920.16.camel@mothafucka.localdomain>
	 <4D3E26E3.3000209@redhat.com>
Content-Type: text/plain; charset="UTF-8"
Organization: Red Hat
Date: Mon, 24 Jan 2011 23:28:37 -0200
Message-ID: <1295918917.15920.17.camel@mothafucka.localdomain>
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Mon, 2011-01-24 at 20:26 -0500, Rik van Riel wrote:
> On 01/24/2011 08:25 PM, Glauber Costa wrote:
> > On Mon, 2011-01-24 at 18:31 -0500, Rik van Riel wrote:
> >> On 01/24/2011 01:06 PM, Glauber Costa wrote:
> >>> Register steal time within KVM. Everytime we sample the steal time
> >>> information, we update a local variable that tells what was the
> >>> last time read. We then account the difference.
> >>>
> >>> Signed-off-by: Glauber Costa<glommer@redhat.com>
> >>> CC: Rik van Riel<riel@redhat.com>
> >>> CC: Jeremy Fitzhardinge<jeremy.fitzhardinge@citrix.com>
> >>> CC: Peter Zijlstra<peterz@infradead.org>
> >>> CC: Avi Kivity<avi@redhat.com>
> >>
> >> On second thought - how does this deal with cpu hotplug and
> >> hot unplug?
> >>
> >> Do you allocate a new one of these structs every time a cpu
> >> is hot unplugged and then hotplugged, leaking the old one?
> >>
> >> Will leaving the old value around confuse the steal time
> >> calculation?
> >
> > If you look closely, there are no allocations happening at all,
> > it's all static.
> 
> In that case, does the per-cpu steal area need to be
> reinitialized at hotplug time?
Probably.

I have to look closely at all unregistration scenarios, like
reboot.
It's part of my todo list