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

To: "Bhatia, Nikhil" <bhatia@xxxxxxxx>, <xen-users@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] Performance Counter Virtualization in Xen
From: "Santos, Jose Renato G" <joserenato.santos@xxxxxx>
Date: Fri, 18 May 2007 20:42:58 -0000
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Thread-topic: [Xen-devel] Performance Counter Virtualization in Xen
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 architectures.


-          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 counters?


-          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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