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IBS not available on EPYC 7451 ?

Question asked by trahay on Jul 17, 2018
Latest reply on Jul 25, 2018 by jlgreathouse

Hi,

I try to use Instruction Based Sampling on a Dell poweredge R7425 machine equipped with 2 EPYC 7451 cpu running on Debian buster (Linux kernel 4.16.0.2, gcc 7.3.0), but neither µProf nor perf_event "see" that IBS is available:

- in µProf, in the "select configuration type", there's no "Instruction-based Sampling" configuration

- "perf list" does not show any ibs_op event, and when I try to use perf_event_open, I get "Invalid argument" errors

 

It seems that the problem is that Linux does not detect IBS: there's no /sys/devices/ibs_op entry in the filesystem, and I can't find any info related to IBS in dmesg output.

I saw on another thread (Instruction Based Sampling broken for Threadripper? ), that IBS may be enabled in BIOS, but I didn't find any option in my machine's BIOS.

 

I tried the AMD research instruction based sampling toolkit (GitHub - jlgreathouse/AMD_IBS_Toolkit: AMD Research Instruction Based Sampling Toolkit ), and it works, so IBS is indeed available, but not through Linux /sys/devices/ibs_op.

 

How could I make IBS work using perf ?

 

Regards

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