TomTheBear
commented
2 years ago There seem to be a cascade of problems here. When you add a raw event string instead of a performance group, the LIKWID library adds the fixed counters at the end of the event string depending on the architecture. Intel Icelake introduces a new fixed counter TOPDOWN_SLOTS:FIXC3 (register 0x30C = access_x86_rdpmc_read (..., reg=780, ...)). Since this is a MSR which can be read throught the RDPMC instruction, it uses it as a faster access method for the read. This instruction seems to fails on your system. It might be that the first perf usage activates the rdpmc instruction (it's just a MSR bit flip but it has to be done in kernel-space). Normally, LIKWID checks the usability of the instruction and otherwise falls back to the rdmsr way. This does not seem to work for you.
When I got my hands on an Icelake SP system the first time, I experienced that the RDPMC instruction failed for the FIXC3 counter, so exactly your problem. I try to investigate that.
Can you please supply some further information:
$ grep -E "model|family|stepping" /proc/cpuinfo | sort -u
$ likwid-perfctr -C 0 -g TOPDOWN_SLOTS:FIXC3 -V 3 hostname
$ perf ....
$ likwid-perfctr -C 0 -g TOPDOWN_SLOTS:FIXC3 -V 3 hostnameUse your "fixing perf command" here or install LIKWID in two different folders with accessdaemon and perf_event mode. I try to spot the difference in the LIKWID execution. If it works for likwid-perfctr, we have to check your code but at the moment, I don't see a problem with your approach.
uenomad
Describe the bug Segmentation fault while reading bandwidth in Ice Lake node 8352Y after reboot.
To Reproduce Is compiled with ACCESSMODE = accessdaemon or direct. If I switch to perf_event, it will run perfectly. Moreover, going back to accessdaemon or direct will be fixed until rebooting the node. Is it possible I'm missing some initialization?
Additional context GDB output:
We load likwid library using dlopen, and the "likwid." is the struct containing the functions. Our initialization code:
Opening events:
And the reading: