Re: [Xen-devel] Re: [Xen-users] About profiling xen

[Marco Tizzoni <marco.tizzoni@xxxxxxxxx>]

On Thu, Oct 1, 2009 at 11:40 PM, Jeremy Fitzhardinge <jeremy@xxxxxxxx> wrote:
> On 10/01/09 14:26, Marco Tizzoni wrote:
>>> OK, good, that takes timers out of the equation.
>>>
>>> I guess the problem is the rate at which Xen will context switch between
>>> two domains.  Hm.
>>>
>>> Does anything change if you pin your domains to different cpus?
>>>
>> mmmh, no. I think without a finer timer the problem could not be solved.
>>
>
> Why's that?  You said that the timers "work as expected", which I read
> to mean that they will generate sub-millisecond events.  Did I
> misunderstand you?

Sorry, I was not clear. It works as I expect, i.e going not over 1000
hz (my dom0 kernel has been compiled with 1000hz).
Following a couple of run of your testtimer:

hal9k-dom0 ~ # ./testtimer .000001 |head -n10
1000 iterations at  0.000001 sec
0.000662
0.000946
0.000956
0.000960
0.000962
0.000956
0.000964
0.000963
0.000964
0.000964

hal9k-dom0 ~ # ./testtimer .00001 |head -n10
1000 iterations at  0.000010 sec
0.000407
0.000942
0.000941
0.000954
0.000956
0.000954
0.000955
0.000932
0.000955
0.000955

Hoping this clarify.

m-

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