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

[Subin_M_]

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,

[Peter_W_Intel]

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_]

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_]

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]

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]

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