Re: [PATCH] perf test: Fix session topology test on heterogeneous systems

["Liang, Kan" <kan.liang@linux.intel.com>]

On 2024-01-22 10:54 a.m., James Clark wrote:
> The test currently fails with this message when evlist__new_default()
> opens more than one event:
> 
>   32: Session topology                                                :
>   --- start ---
>   templ file: /tmp/perf-test-vv5YzZ
>   Using CPUID 0x00000000410fd070
>   Opening: unknown-hardware:HG
>   ------------------------------------------------------------
>   perf_event_attr:
>     type                             0 (PERF_TYPE_HARDWARE)
>     config                           0xb00000000
>     disabled                         1
>   ------------------------------------------------------------
>   sys_perf_event_open: pid 0  cpu -1  group_fd -1  flags 0x8 = 4
>   Opening: unknown-hardware:HG
>   ------------------------------------------------------------
>   perf_event_attr:
>     type                             0 (PERF_TYPE_HARDWARE)
>     config                           0xa00000000
>     disabled                         1
>   ------------------------------------------------------------
>   sys_perf_event_open: pid 0  cpu -1  group_fd -1  flags 0x8 = 5
>   non matching sample_type
>   FAILED tests/topology.c:73 can't get session
>   ---- end ----
>   Session topology: FAILED!
> 
> This is because when re-opening the file and parsing the header, Perf
> expects that any file that has more than one event has the session ID
> flag set. Perf record already sets the flag in a similar way when there
> is more than one event, so add the same logic to evlist__new_default().
> 
> evlist__new_default() is only currently used in tests, so I don't
> expect this change to have any other side effects.
> 
> The session topology test has been failing on Arm big.LITTLE platforms
> since commit 251aa040244a ("perf parse-events: Wildcard most
> "numeric" events") when evlist__new_default() started opening multiple
> events for 'cycles'.
> 
> Fixes: 251aa040244a ("perf parse-events: Wildcard most "numeric" events")
> Signed-off-by: James Clark <james.clark@arm.com>
Verified on an Intel hybrid machine.

Tested-by: Kan Liang <kan.liang@linux.intel.com>

Thanks,
Kan


> ---
>  tools/perf/util/evlist.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
> index 95f25e9fb994..56db37fac6f6 100644
> --- a/tools/perf/util/evlist.c
> +++ b/tools/perf/util/evlist.c
> @@ -95,6 +95,7 @@ struct evlist *evlist__new_default(void)
>  	struct evlist *evlist = evlist__new();
>  	bool can_profile_kernel;
>  	int err;
> +	struct evsel *evsel;
>  
>  	if (!evlist)
>  		return NULL;
> @@ -106,6 +107,10 @@ struct evlist *evlist__new_default(void)
>  		evlist = NULL;
>  	}
>  
> +	if (evlist->core.nr_entries > 1)
> +		evlist__for_each_entry(evlist, evsel)
> +			evsel__set_sample_id(evsel, false);
> +
>  	return evlist;
>  }
>