[PATCH] perf print-events: make is_event_supported() more robust

[Marc Zyngier]

Hi Mark,

On Tue, 16 Jan 2024 17:03:48 +0000,
Mark Rutland <mark.rutland at arm.com> wrote:
> 
> Currently the perf tool doesn't deteect support for extneded event types
> on Apple M1/M2 systems, and will not auto-expand plain PERF_EVENT_TYPE
> hardware events into per-PMU events. This is due to the detection of
> extended event types not handling mandatory filters required by the
> M1/M2 PMU driver.

Thanks for looking into this.

I've given your patch a go on my M1 box, and it indeed makes things
substantially better:

$ sudo ./perf stat -e cycles ~/hackbench 100 process 1000
Running with 100*40 (== 4000) tasks.
Time: 3.419

 Performance counter stats for '/home/maz/hackbench 100 process 1000':

   174,783,472,090      apple_firestorm_pmu/cycles/                                             (93.10%)
    39,134,744,813      apple_icestorm_pmu/cycles/                                              (71.86%)

       3.568145595 seconds time elapsed

      12.203084000 seconds user
      55.135271000 seconds sys

However, I'm seeing some slightly odd behaviours:

$ sudo ./perf stat -e cycles:k ~/hackbench 100 process 1000
Running with 100*40 (== 4000) tasks.
Time: 3.313

 Performance counter stats for '/home/maz/hackbench 100 process 1000':

   <not supported>      apple_firestorm_pmu/cycles:k/                                         
   <not supported>      apple_icestorm_pmu/cycles:k/                                          

       3.467568841 seconds time elapsed

      13.080111000 seconds user
      53.162099000 seconds sys

I would have expected it to count, but it didn't. For that to work, I
have to add the 'H' modifier:

$ sudo ./perf stat -e cycles:Hk ~/hackbench 100 process 1000
Running with 100*40 (== 4000) tasks.
Time: 3.335

 Performance counter stats for '/home/maz/hackbench 100 process 1000':

   183,756,134,397      apple_firestorm_pmu/cycles:Hk/                                          (85.56%)
    37,302,841,991      apple_icestorm_pmu/cycles:Hk/                                           (72.10%)

       3.490138958 seconds time elapsed

      13.376772000 seconds user
      53.326289000 seconds sys

But my perf-foo is as basic as it gets, so it is likely that I'm
missing something.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.