Perf stat not functioning

[tomhepworth]

If I use perf stat the cycles and instruction events show <not counted> about 99% of the time. Has anyone else had any luck with perf? Could something perhaps be wrong with the driver? I am on an M1 Mac Mini.

perf stat -e cycles,instructions ls

     <not counted>      cycles:u                                                      (0.00%)
     <not counted>      instructions:u                                                (0.00%)

       0.000535494 seconds time elapsed

       0.000555000 seconds user
       0.000000000 seconds sys

[adamtuby]

Hey, the performance counters on the M1 architecture are pretty much disabled considering all of the available performance counters are EL1 privilege and up. I'm currently trying to write a kernel module to expose those performance counters to userspace. Currently, I'm failing to do so with asahilinux, but able to do so on macOS.

update:
It seems as if asahi didn't expose the system registers of the M1 through the hypervisor. I'm unable to read (nor edit) very simple EL0 registers such as CNTPCT_EL0 on asahi but I'm able to do so on macOS.

[tomhepworth]

I have been in to the IRC rooms and got help to solve my problem. Specifying a core will yield results.

I am now using a command like:

sudo taskset --cpu-list 0 perf stat -C 0 -e apple_firestorm_pmu/cycles/ -e apple_icestorm_pmu/cycles/ -e apple_firestorm_pmu/instructions/ -e apple_icestorm_pmu/instructions/ awk 'BEGIN{for(i=0;i<1000000;i++){}}'

to profile a program on a specific core.