topic How would you do this in the in Software Tuning, Performance Optimization & Platform Monitoring

how to use rdmsr from my C program?

anthony_b_ — Wed, 11 May 2016 10:41:49 GMT

From intel software developer manual 3b, I came to know MSR (10H) equal to RDTSC. So I wanted to verify it using piece of code as follows in my program:

asm volatile("rdmsr":"=a"(lo),"=d"(hi):"c"(0x10));

But when I run my program it showed segmentation fault. Then a realized the caution that it work only in privilege level 0. So I run the program again with sudo access. This time the program ran without seg fault but the statement after asm volatile(..) are not getting executed. Even it dint work out.

What shall I do to make rdmsr work in my program?
(I am using linux on i7 core which supports these counters. I verified it.)

Thank you

How would you do this in the

Adrian_C_ — Mon, 13 Mar 2017 18:55:09 GMT

How would you do this in the Windows OS?

I don't know whether there is

Thomas_G_4 — Fri, 17 Mar 2017 11:06:23 GMT

I don't know whether there is a WindowsOS native way to access the MSRs, probably through some debugging interface or such.

You can use the Windows driver from Intel PCM https://github.com/opcm/pcm to get an interface to the user space. For further information see the Windows HOWTO https://github.com/opcm/pcm/blob/master/WINDOWS_HOWTO.rtf

Here is also a link with some explanations how to install the driver: https://software.intel.com/en-us/forums/software-tuning-performance-optimization-platform-monitoring/topic/371243

If it will be helpfull - good

SB17 — Thu, 06 Apr 2017 17:08:05 GMT

If it will be helpfull - good examples of how to use rd/wrmsr is the source code of Intel Performance Counter Monitor and Likwid.