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

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Date:	Mon, 24 Jan 2011 20:26:59 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Glauber Costa <glommer@...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 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?

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