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Beginner
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register_kretprobe('do_fork') failed: -2

Hello

vtune installation finished without error:
$ lsmod |egrep 'pax|sep3_15|vtsspp'
vtsspp                360448  0
sep3_15               557056  0
pax                    16384  0

but when amplxe-cl -collect is launched I get the following error:
$ dmesg
[ 3609.758638] vtss_pebs_init[cpu10]: PEBS: size=0xC0, mask=0xF, family = 6, model = 3f
[ 3609.771611] probe_sched_process_fork[cpu10]: register_kretprobe('do_fork') failed: -2
[ 3613.868145] vtss_collection_fini[cpu10]: vtss++ collection stopped 0
[ 3613.868686] NMI watchdog: enabled on all CPUs, permanently consumes one hw-PMU counter.
[ 3613.879365] vtss_transport_fini[cpu5]: Transport stopped.

I have seen that parallel_studio_xe_2016_update2 is supposed to work with Fedora 23, could you please help me fix this problem ?

Fedora 23
Kernel 4.4.4-301.fc23.x86_64
Intel i7-5820K

Best Regards

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Employee
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VTune(TM) Amplifier XE 2016 Update 2 supported Fedora* 23 which kernel is version 4.2.3-300. Maybe you used update kernel which was not tested by VTune Amplifier?

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Employee
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I had no problem to do advanced-hotspots on FC23.

[root@localhost ~]# cat /etc/redhat-release
Fedora release 23 (Twenty Three)
[root@localhost ~]# uname -a
Linux localhost.localdomain 4.2.3-300.fc23.x86_64 #1 SMP Mon Oct 5 15:42:54 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

[root@localhost ~]# amplxe-cl -version
Intel(R) VTune(TM) Amplifier XE 2016 Update 2 (build 444464) Command Line Tool

[root@localhost ~]# lsmod | egrep 'pax|sep|vtsspp'
vtsspp                360448  0
sep3_15               561152  0
pax                    16384  0

[root@localhost ~]# amplxe-cl -c advanced-hotspots -d 5
amplxe: Error: System-wide collection is not possible due to a lack of credentials. Consider setting the /proc/sys/kernel/perf_event_paranoid value to 0 or less.
[root@localhost ~]# echo 0 | tee /proc/sys/kernel/perf_event_paranoid
There was no problem to redo advanced-hotspots analysis.

Do you work on Virtual Machine? Actually I installed FC23 on KVM and VTune(TM) Amplifier XE works.

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Beginner
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Hello Peter

Thanks for your answers
I am not working in a Virtual Machine.
But you are right, I often perform 'sudo dnf update' and it sometimes installs a new kernel.
I guess that if you do the same you'll be able to reproduce.
I think that I still have the 4.2.3-300.fc23.x86_64 kernel, so I'll try tonight to reinstall vtune with this kernel.

By the way I am not sure that the register_kretprobe('do_fork') is completely blocking (I am a very new vtune user):
I haven't seen any PMU event collected while I was running an advanced-hotspots analysis
but I think I've seen some while running a general-exploration one.
What do you think ?

Regards

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Beginner
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Hello

I confirm that there is no error with the fedora 23 release kernel (4.2.3). example output in attached file 4.2.3.txt

But the same command with current fedora 23 kernel (4.4.4) gives the attached 4.4.4.txt file

Also I noticed that the "register_kretprobe('do_fork') failed" error message only occurs when the option -knob collection-detail=stack-and-callcount is used. But again I am not sure of the impact of this error.

Regards

 

 

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Employee
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"register_kretprobe('do_fork') failed" error message meant, inserted probes in kernel returned FALSE when forking process.

I don't know why and probably Linux* kernel 4.4.4 hasn't been supported (tested) yet. So, please use kernel 4.2.3 which is workable with VTune Amplifier. And I tried option "-knob collection-detail=stack-and-callcount" based on kernel 4.2.3, no problem (If you have this issue, please provide specific test case and we will investigate). Thank you.

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Hello,

Linux kernel 4.4 support will be released in future versions of VTune and is not available in the Update 2. We will verify the reported issue is addressed. Thanks for reporting!

Regards, Katya

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