Intel PCM and CPU hotplug Issue

raoufeh — Mon, 23 Apr 2012 18:15:05 GMT

Hi all,

I was using the Intel PCM in an 8 core (SMT-16thread) Intel server and it was doing fine. Recently, I needed to run my experiments while diableing some cores using CPU hotplug capability of Linux (http://www.cyberciti.biz/faq/debian-rhel-centos-redhat-suse-hotplug-cpu/)

But when I try to run the PCM while some of the cores are disabled I get the following error:

Can not access CPUs Model Specific Registers (MSRs).
Try to execute 'modprobe msr' as root user and then
you also must have read and write permissions for /dev/cpu/*/msr devices (the 'chown' command can help).

Nothing has changed in the system in terms of permission and the msr module is added using modprobe. So I guess PCM tries to access the folders for diabled cores in /dev/cpu/* and since hotplug removes the folder for the diabled cores, this error is generated.

I was wondering if there is a way to solve this problem? or if the developers are aware of this issue?

Thanks,
Cheers,
RSH

Intel PCM and CPU hotplug Issue

Roman_D_Intel — Tue, 24 Apr 2012 15:45:24 GMT

Hi RSH,

thanks for reporting this. So far we did not look at the systems with cores disabled by OS. We shouldfind outhow we can prioritize this requestto find a simple solution for such configurations.

Thanks,
Roman

topic Intel PCM and CPU hotplug Issue in Software Tuning, Performance Optimization & Platform Monitoring

Intel PCM and CPU hotplug Issue

Intel PCM and CPU hotplug Issue