linux-kernel - Re: [PATCH 14/16] KVM-GST: KVM Steal time registration

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Date:	Mon, 24 Jan 2011 23:28:37 -0200
From:	Glauber Costa <glommer@...hat.com>
To:	Rik van Riel <riel@...hat.com>
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	aliguori@...ibm.com,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Avi Kivity <avi@...hat.com>
Subject: Re: [PATCH 14/16] KVM-GST: KVM Steal time registration

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@...hat.com>
> >>> CC: Rik van Riel<riel@...hat.com>
> >>> CC: Jeremy Fitzhardinge<jeremy.fitzhardinge@...rix.com>
> >>> CC: Peter Zijlstra<peterz@...radead.org>
> >>> CC: Avi Kivity<avi@...hat.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

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