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

To: Marco Tizzoni <marco.tizzoni@xxxxxxxxx>
Subject: Re: [Xen-devel] Re: [Xen-users] About profiling xen
From: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Date: Thu, 01 Oct 2009 15:01:59 -0700
Cc: "Fajar A." <fajar@xxxxxxxxx>, Fasiha Ashraf <feehapk@xxxxxxxxxxx>, xen <xen-devel@xxxxxxxxxxxxxxxxxxx>, xen-users@xxxxxxxxxxxxxxxxxxx
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On 10/01/09 14:55, Marco Tizzoni wrote:
> 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).

OK, that's definitely *not* expected.  If you're running with
CONFIG_NO_HZ and HIGH_RES_TIMERS then timer resolution should have
nothing to do with your HZ configuration.

> Following a couple of run of your testtimer:
> hal9k-dom0 ~ # ./testtimer .000001 |head -n10

I think expecting a timer to work at 1MHz is unreasonable.

> 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
100kHz is also very demanding.

How does it work with 2kHz? 10kHz?


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