linux-kernel - Re: [PATCH 4/4] Add a timer to allow the separation of consigned from steal time.

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Message-ID: <511369CC.6050405@parallels.com>
Date:	Thu, 7 Feb 2013 12:46:04 +0400
From:	Glauber Costa <glommer@...allels.com>
To:	Michael Wolf <mjw@...ux.vnet.ibm.com>
CC:	<linux-kernel@...r.kernel.org>, <riel@...hat.com>,
	<gleb@...hat.com>, <kvm@...r.kernel.org>, <peterz@...radead.org>,
	<mtosatti@...hat.com>, <mingo@...hat.com>, <anthony@...emonkey.ws>
Subject: Re: [PATCH 4/4] Add a timer to allow the separation of consigned
 from steal time.

On 02/06/2013 10:07 PM, Michael Wolf wrote:
> On 02/06/2013 08:36 AM, Glauber Costa wrote:
>> On 02/06/2013 01:49 AM, Michael Wolf wrote:
>>> Add a helper routine to scheduler/core.c to allow the kvm module
>>> to retrieve the cpu hardlimit settings.  The values will be used
>>> to set up a timer that is used to separate the consigned from the
>>> steal time.
>> Sorry: What is the business of a timer in here?
>> Whenever we read steal time, we know how much time has passed and with
>> that information we can know the entitlement for the period. This breaks
>> if we suspend, but we know that we suspended, so this is not a problem.
> I may be missing something, but how do we know how much time has
> passed?  That is why
> I had the timer in there.  I will go look again at the code but I
> thought the data was collected
> as ticks and passed at random times.  The ticks are also accumulating so
> we are looking at the
> difference in the count between reads.....

They can be collected at random times, but you can of course record the
time in which it happened.

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