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

To: Pasi Kärkkäinen <pasik@xxxxxx>
Subject: Re: [Xen-devel] Re: [Xen-users] About profiling xen
From: Marco Tizzoni <marco.tizzoni@xxxxxxxxx>
Date: Wed, 30 Sep 2009 08:40:45 +0200
Cc: "Fajar A." <fajar@xxxxxxxxx>, Fasiha Ashraf <feehapk@xxxxxxxxxxx>, xen <xen-devel@xxxxxxxxxxxxxxxxxxx>, xen-users@xxxxxxxxxxxxxxxxxxx
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On Wed, Sep 30, 2009 at 8:37 AM, Pasi Kärkkäinen <pasik@xxxxxx> wrote:
> On Wed, Sep 30, 2009 at 08:33:19AM +0200, Marco Tizzoni wrote:
>>    I experienced the same problem with netperf and with hping also. In
>>    general every tool that sends packet at fixed rates seems to suffer this
>>    problem. If you use the flood option ( sends packets as fast as possible -
>>    for example 'ping -f' or 'hping3 -f') instead of a fixed rate the rate
>>    become much higher. What I discovered is this issue should be related to
>>    Xen's signal handling/delivery.
>>    Netperf use setitimer() to send packets at fixed rate. In my experience on
>>    dom0/U, with no load, Xen cannot go over 250 signals per second. Because
>>    netperf use signal wakeup the function that send packets I think your
>>    problem can be related to this issue. If you want to be sure, count the
>>    average number of packet per seconds. It should be about 250 packets/s
>>    (not more).
> 250 per second.. sounds like kernel HZ value?

Yes, infact I'm going to test it with 1000Khz. Stay tuned.



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