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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 14:16:56 -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 14:05, Marco Tizzoni wrote:
>> The clock*event* mechanism is all about setting up timers to raise events.
>> When running paravirtualized, we use Xen-specific versions of both.
> Ok.  My problem is granularity. In xen I can't raise events more
> frequently than 1000/s (with timer set to 1000hz).
> Net test softwares such as netperf or hping use setitimer to send
> packet at a fixed rate. On a non-xen box they works fine even  with
> 100k packets/sec (i.e. 100k alarms/sec). This can be problematic for
> streaming software and more in general for soft real-time
> applications.
> [...]
> Thanks for your test, I tried and timers work as expected.

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?


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