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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: Pasi Kärkkäinen <pasik@xxxxxx>
Date: Wed, 30 Sep 2009 09:37:47 +0300
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 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? 

-- Pasi

>    For more info you can see
> this:[1]http://lists.xensource.com/archives/html/xen-devel/2009-09/msg01159.html
>    Regards.
>    Marco
>    On Wed, Sep 30, 2009 at 8:07 AM, Fasiha Ashraf <[2]feehapk@xxxxxxxxxxx>
>    wrote:
>      Hi there,
>      I am getting very low throughput (around 0.29Mbps) while running netperf
>      benchmark for guest to guest communication on a single physical host. To
>      analyse where the time is spent in hypervisor I wanna use profiling.
>      Please help me choosing good profiler according to my requirments.
>      Should it be better in my case, Xentrace, gprof, xenoprof  or Oprofile.
>      Is it possible to use some vtune version on FC11?
> References
>    Visible links
>    1. http://lists.xensource.com/archives/html/xen-devel/2009-09/msg01159.html
>    2. mailto:feehapk@xxxxxxxxxxx

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