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

On Wed, Jan 17, 2024 at 09:05:25AM +0000, Marc Zyngier wrote:

Hi Mark,

On Tue, 16 Jan 2024 17:03:48 +0000,
Mark Rutland [off-list ref] wrote:

quoted

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

Thanks for giving that a spin!

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:

Ok, so that'll have something to do with the way the tool chooses which
perf_evant_attr::exclude_* bits to set. I thought that was the same for plain
events and pmu_name/event/ events, but I could be mistaken.

Is that something you had tried prior to this patch, and did that "just work"
with the explicit pmu_name/event/ syntax prior to this patch?

e.g. did something like:

	perf stat -e apple_firestorm_pmu/cycles/k -e apple_icestorm_pmu/cycles/k ./workload

... happen to work withiout requiring the addition of 'H'?

If so, does that behave the same before/after this patch?

... and could you run that with '-vvv' and dump the output for comparison?

Thanks,
Mark.

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