[Xen-devel] Re: XENOPROF Problem

[Andrew Evans <andrewe@xxxxxxxxxxxxx>]

Hi Ahmad,

I'm certainly not a Xenoprof expert, but I've learned a bit about it by trial and error, with help from the xen-devel list. I've taken the liberty of Cc:ing xen-devel so that others more knowledgeable than me can help you. I haven't tried passive domains yet, and I'll say up front that I don't know why Xenoprof isn't working for you with passive domains.

On 02/11/10 13:37, Ahmad Hassan wrote:

Hi Andrew,

I need help in using xenoprof. I installed the xenoprof on Dom0 and DomU as follows:

• Download Oprofile: http://prdownloads.sourceforge.net/oprofile/oprofile-0.9.5.tar.gz
• Download XenoProf patch: http://xenoprof.sourceforge.net/oprofile-0.9.5-xen.patch
  
• tar –zxvf oprofile-0.9.5.tar.gz
• cd oprofile-0.9.5
• patch –p1 < ../oprofile-0.9.5-xen-rc2.patch ./configure –with-kernel-support
• make
• make install

That looks right to me. You also need Xenoprof support in your dom0 kernel. If you're using one of the kernels from the Xen source tree and you can `modprobe oprofile` successfully, you should be ok.

I am interested in measuring profiling overhead in XEN. So which kind of event should I capture.

You want to measure the overhead of the profiler itself? I guess you get that "for free" -- time spent in oprofile kernel code should show up in opreport in dom0, I think.

Which performance counter you use depends on what you're trying to measure. If you just want to find out where CPU time is spent, CPU_CLK_UNHALTED should do that for you. That's what I've been doing.

Is it possible to capture all the events?

You can specify multiple events, though I haven't tried it. The opreport web page talks about output for multiple events here:

http://oprofile.sourceforge.net/doc/opreport.html#opreport-comparison

I'd guess you'd just specify --event multiple times when you --start-daemon.

  I followed the following passive profiling approach but I did not get any data.

Dom0: opcontrol --reset
Dom1: opcontrol --reset
Dom0: opcontrol --start-daemon --event= CPU_IO_REQUESTS_TO_MEMORY_IO:1000000 --xen=/boot/xen-syms-3.4.1   --vmlinux=/boot/vmlinux  --passive-domains=1 --passive-images=/boot/vmlinux
At the above command, I get the warning as : /dev/oprofile/passive-domains Permission Denied but daemon starts eventually

This is a silly question, but you are running this as root, correct? If you are running as root and getting this error, I think something is wrong either in Xen or your dom0 kernel. `xm dmesg` may have error messages that give clues -- check it before and after starting the daemon.

Dom0: opcontrol --start
AFTER 30 MINUTE
Dom0: opcontrol –stop
Dom0: opcontrol --dump
Dom0: opcontrol –shutdown

But when I try to "opreport -l" ti says that: "opreport error: No sample file found: try running opcontrol --dump or specfiy a session containing sample file"


Can you please help me in that?

Thanks.

Best Regards, Hassan
http://cern.ch/ahmadh/portfolio

Erasmus Student
The University of Reading, UK
Aristotle University of Thessaloniki, Greece
The University Of Carlos III, Madrid Spain

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel