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Call-stack data collection stalls when KVM based VM is running on the Host

Subin_M_
Beginner
128 Views

Hi there,

I am facing a problem while doing a system-wide callstack analysis using vtune_2015 Update 2 on an ubuntu 14.04 server.

If I start a VM(KVM based) and then do "/opt/intel/vtune_amplifier_xe/bin64/amplxe-cl -collect advanced-hotspots -knob collection-detail=stack-sampling --duration 20 -result-dir ~/intel/amplxe/projects/a/b", on the HOST, the profiling starts. Once the profiling is done amplxe always gets stuck displaying the below message

"amplxe: Executing actions  8 % Loading 'system-wide.perf' file"

Irrespective of the duration, I always get the same 8% progress bar.

Interestingly, everything works fine in the below cases:

     i) If I don't have any VMs running on the HOST and I do  a call-stack based profiling.

    ii)If I have VMs running, and I just do a advanced-hotspots profiling(without the call-stack)

I am interested in profiling the kernel when VMs are running. And I really want the call-stacks as well.

Can someone please shed some light on why I can't get the call-stack profiling when a VM process is running.

Thanks,

0 Kudos
5 Replies
Peter_W_Intel
Employee
128 Views

As we discuss on other tread that KVM is not officially supported for PMU even-based sampling, please work Linux* as host operation system.

If you work on Linux* based on VM, please use basic hotspots instead of advanced hotspots. 

Subin_M_
Beginner
128 Views

Hi Peter,

Thanks for the quick response..

Basic Hotspots does not support system-wide profiling right?

I am not interested in profiling the VM/any user process. I wanted to profile the Host Network stack while a VM is running.

The PMU is still available to the Host even though a KVM based VM is running, isn't it?

vtune does complete the profile with call-stack information. It just gets stuck in the data parsing phase.

Looks like a small bug, am I missing something very basic here.. Please let me know.

Thanks..

Subin_M_
Beginner
128 Views

Note that, even if a VM is running in system and I profile the host, the advanced-hotspots option works fine if I don't add the call-stack knob.

Thanks..

Vitaly_S_Intel
Employee
128 Views

Hi Subin,

Engineering team still wants to analyze the reason of hang on loading of .perf file. Can you send it to me via private message?

Thanks!

Vitaly_S_Intel
Employee
128 Views

Based on the data I got from Subin this is known issue which was fixed in Update 3 (already available for download).

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