Re: [PATCH 7/8] perf tools: Add fallback for exclude_guest

[James Clark <james.clark@linaro.org>]

On 04/09/2024 7:41 am, Namhyung Kim wrote:
> It seems Apple M1 PMU requires exclude_guest set and returns EOPNOTSUPP
> if not.  Let's add a fallback so that it can work with default events.
> 
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: James Clark <james.clark@linaro.org>
> Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> ---
>   tools/perf/util/evsel.c | 21 +++++++++++++++++++++
>   1 file changed, 21 insertions(+)
> 
> diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
> index 0de0a72947db3f10..8c4d70f7b2f5b880 100644
> --- a/tools/perf/util/evsel.c
> +++ b/tools/perf/util/evsel.c
> @@ -3400,6 +3400,27 @@ bool evsel__fallback(struct evsel *evsel, struct target *target, int err,
>   			  "to fall back to excluding hypervisor samples", paranoid);
>   		evsel->core.attr.exclude_hv = 1;
>   
> +		return true;
> +	} else if (err == EOPNOTSUPP && !evsel->core.attr.exclude_guest &&
> +		   !evsel->exclude_GH) {
> +		const char *name = evsel__name(evsel);
> +		char *new_name;
> +		const char *sep = ":";
> +
> +		/* Is there already the separator in the name. */
> +		if (strchr(name, '/') ||
> +		    (strchr(name, ':') && !evsel->is_libpfm_event))
> +			sep = "";
> +
> +		if (asprintf(&new_name, "%s%su", name, sep) < 0)
> +			return false;
> +
> +		free(evsel->name);
> +		evsel->name = new_name;
> +		/* Apple M1 requires exclude_guest */
> +		scnprintf(msg, msgsize, "trying to fall back to excluding guest samples");
> +		evsel->core.attr.exclude_guest = 1;
> +
>   		return true;
>   	}
>   

Not sure if this is working, for some reason it doesn't try the 
fallback. With exclude guest made mandatory in the Arm PMU, then:

  $ perf stat -e cycles -vvv -- true

   Control descriptor is not initialized
   Opening: cycles
   ------------------------------------------------------------
   perf_event_attr:
     type                             0 (PERF_TYPE_HARDWARE)
     size                             136
     config                           0xb00000000
     sample_type                      IDENTIFIER
     read_format                      TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
     disabled                         1
     inherit                          1
     enable_on_exec                   1
   ------------------------------------------------------------
   sys_perf_event_open: pid 698  cpu -1  group_fd -1  flags 0x8
   sys_perf_event_open failed, error -95
   Warning:
   cycles event is not supported by the kernel.
   Opening: cycles
   ------------------------------------------------------------
   perf_event_attr:
     type                             0 (PERF_TYPE_HARDWARE)
     size                             136
     config                           0xa00000000
     sample_type                      IDENTIFIER
     read_format                      TOTAL_TIME_ENABLED|TOTAL_TIME_RUNNING
     disabled                         1
     inherit                          1
     enable_on_exec                   1
   ------------------------------------------------------------
   sys_perf_event_open: pid 698  cpu -1  group_fd -1  flags 0x8
   sys_perf_event_open failed, error -95
   Warning:
   cycles event is not supported by the kernel.
   failed to read counter cycles
   failed to read counter cycles

    Performance counter stats for 'true':

      <not supported>      armv8_cortex_a53/cycles/ 

      <not supported>      armv8_cortex_a57/cycles/ 




Other than that, all the tests are passing on Juno (without the 
exclude_guest requirement).