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Re: [Xen-devel] Performance Counter Virtualization in Xen

Well it's not "x86 architectures", but the current profiling support in xen on powerpc allows the use of performance counters from the domains as used from non-virtualized environments. It is currently only tested with oprofile and has to be considered experimental because there are some known issues, but depending on your needs this might work for you. As far as I read on http://icl.cs.utk.edu/papi/custom/index.html?lid=62&slid=96 PAPI has PPC970 support. I do not know PAPI in detail, but it is possible that you can run it with less/no patching xen/linux on the current xenppc head.

Santos, Jose Renato G wrote:
You are right, currently the only available tool for using hardware performance counters in Xen is XenOprofile. To expose a more generic API to guests such as Perfmon, we would need to virtualize performance counters. One of the challenges of virtualizing performance counters is the high cost of saving and restoring perf. counters on domain context switches. It may be possible to do some optimizations such as lazy save/restore that could help. Also it is expected that the cost for accessing performance counters is going to be better in new processors that are coming out from Intel and AMD. afaik, no one is actively working on virtualizing HW performance counters in Xen. For other software metrics such as number of I/O operations you can try Xenmon which report values of Xen performance counters (i.e SW counters).

    *From:* xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
    [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] *On Behalf Of
    *Bhatia, Nikhil
    *Sent:* Friday, May 18, 2007 12:15 PM
    *To:* xen-users@xxxxxxxxxxxxxxxxxxx
    *Cc:* xen-devel@xxxxxxxxxxxxxxxxxxx
    *Subject:* [Xen-devel] Performance Counter Virtualization in Xen

    Hello Xenthusiasts,

    I have a few questions regarding the performance monitoring of
    applications and domains running on the latest version of Xen VMM
    via the performance monitoring counters available in x86

    -          I have used Xenoprof by patching Xen-3.0.2 Xenolinux
    and the Oprofile layer which enabled me to collect performance
    counter values per domain (for a passive domain) and per
    application (for an active domain). I was able to perform the
    profiling via command line interface using Opcontrol and then
    reporting the counters using Opreport. However, I was unable to
    find a way to profile an application (using an API like PAPI)
    because the perfctr port was not available for Xen. Is there a way
    through which applications can be monitored using performance

    -          Is there a Xen tool/utility which provides meaningful
    information about per-domain metrics for dynamic memory usage
    (e.g. reserved memory by Xen, total heap size in use, swap space
    reserved per domain etc.), I/O done to/from the disc and the bytes
    sent/received from the network over fixed intervals of time?


    Best Regards,



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