Re: kvm ppc timing stats

[Hollis Blanchard <hollis_blanchard@mentor.com>]

I don't think the numbers added up like that for us either. We treated 
them as relative data, not absolute.

I don't remember how early/late the timestamps were recorded, but 
obviously they cannot cover 100% of the handler. As the number of exits 
increases, those unaccounted-for instructions would add up... but I 
wouldn't expect that to cause errors of the magnitude you're seeing. 
Perhaps there is a more obvious problem with the way certain exit types 
are recorded (or not recorded).

Hollis Blanchard
Mentor Graphics, Embedded Systems Division


On 12/01/2010 08:18 PM, Yoder Stuart-B08248 wrote:
> Well, in the example I'm looking at, which runs for 30
> seconds, the "sum" column of the stats adds up to
> about 10 seconds total.   So, there is 20 seconds
> unaccounted for.
>
> Interestingly enough, if I let the guest just sit
> idle for 30 seconds, the stats do sum up to about
> 30 seconds.
>
> Will get to the bottom of it, but wanted to make
> sure I was not missing something obvious.
>
> Stuart
>
>
>> -----Original Message-----
>> From: Hollis Blanchard [mailto:hollis_blanchard@mentor.com]
>> Sent: Wednesday, December 01, 2010 6:27 PM
>> To: Yoder Stuart-B08248
>> Cc: kvm-ppc@vger.kernel.org
>> Subject: Re: kvm ppc timing stats
>>
>> Yes, your understanding is correct (barring any bugs, of course). Why
> do
>> you think "time is missing"?
>>
>> Hollis Blanchard
>> Mentor Graphics, Embedded Systems Division
>>
>>
>> On 12/01/2010 12:02 PM, Yoder Stuart-B08248 wrote:
>>> Hollis,
>>>
>>> Am looking at some performance data and want to make sure that
>>>
>>> I'm understanding things correctly with your CONFIG_KVM_EXIT_TIMING
>>>
>>> stuff.   If I reset the timing counters, run a workload
>>>
>>> under for a fixed duration (e.g. 30 seconds), and then look
>>>
>>> at the exit stats, I should see 30 seconds worth of time accounted
>>>
>>> for, correct?
>>>
>>> Right now I'm seeing a substantial amount of time "missing" and
>>>
>>> want to make sure I'm not missing something.
>>>
>>> Stuart
>>>
>