[PATCH v3 2/7] perf metric: Event "Compat" value supports matching multiple identifiers

[John Garry]

On 19/06/2023 09:59, Jing Zhang wrote:
>> Please verify running these metrics with 'perf stat', like 'perf stat -v -M slc_miss_rate'
>>
> Ok, it shows:
> #./perf stat -v -M slc_miss_rate sleep 1
> 
> metric expr hnf_cache_miss / hnf_slc_sf_cache_access for slc_miss_rate
> found event duration_time
> found event hnf_slc_sf_cache_access

In the earlier RFC series you had 
tools/perf/pmu-events/arch/arm64/arm/cmn700/sys/cmn.json, which 
describes event hnf_slc_sf_cache_access

But that JSON is not in this series. Why is it not included?

The cmn kernel driver exposes event hnf_slc_sf_cache_access, but I did 
not think that perf tool metric code matches those events described in 
/bus/event_sourcs/devices/<PMU>/events

> found event hnf_cache_miss
> Parsing metric events '{hnf_slc_sf_cache_access/metric-id=hnf_slc_sf_cache_access/,hnf_cache_miss/metric-id=hnf_cache_miss/}:W,duration_time'
> hnf_slc_sf_cache_access -> arm_cmn_0/type=0x5,eventid=0x2/
> hnf_slc_sf_cache_access -> arm_cmn_1/type=0x5,eventid=0x2/
> hnf_cache_miss -> arm_cmn_0/type=0x5,eventid=0x1/
> hnf_cache_miss -> arm_cmn_1/type=0x5,eventid=0x1/
> Control descriptor is not initialized
> hnf_slc_sf_cache_access: 127615 1001344900 1001344900
> hnf_cache_miss: 36829 1001344900 1001344900
> hnf_slc_sf_cache_access: 131526 1001343540 1001343540
> hnf_cache_miss: 40587 1001343540 1001343540
> duration_time: 1001381687 1001381687 1001381687
> 
>   Performance counter stats for 'system wide':
> 
>             259,141      hnf_slc_sf_cache_access   #     29.9 %  slc_miss_rate
>              77,416      hnf_cache_miss
>       1,001,381,687 ns   duration_time
> 
>         1.001381687 seconds time elapsed
> 
> 
> 
> #./perf list
> ...
>   arm_cmn_0/hnf_cache_miss/                          [Kernel PMU event]
>   arm_cmn_0/hnf_slc_sf_cache_access/                 [Kernel PMU event]
> ...
>   arm_cmn_1/hnf_cache_miss/                          [Kernel PMU event]
>   arm_cmn_1/hnf_slc_sf_cache_access/                 [Kernel PMU event]
> ...
> 
>>> In the past, I always thought that the function of the alias was to explain the meaning of these events in the perf list.
>>> Or maybe I'm missing something?
>> Event aliases do give the ability to describe the event in perf list. But we can also run them for 'perf stat', like:
>>
>> ./perf list uncore
>> List of pre-defined events (to be used in -e or -M):
>>
>>    uncore_cbox_0/clockticks/                          [Kernel PMU event]
>>    uncore_cbox_1/clockticks/                          [Kernel PMU event]
>>    uncore_imc/data_reads/                             [Kernel PMU event]
>>    uncore_imc/data_writes/                            [Kernel PMU event]
>>    uncore_imc/gt_requests/                            [Kernel PMU event]
>>    uncore_imc/ia_requests/                            [Kernel PMU event]
>>    uncore_imc/io_requests/                            [Kernel PMU event]
>>
>> uncore cache:
>>    unc_cbo_cache_lookup.any_es
>>         [L3 Lookup any request that access cache and found line in E or S-state. Unit: uncore_cbox]
>> ...
>>
>> sudo ./perf stat -v -e unc_cbo_cache_lookup.any_es
>> Using CPUID GenuineIntel-6-3D-4
>> unc_cbo_cache_lookup.any_es -> uncore_cbox_0/event=0x34,umask=0x86/
>> unc_cbo_cache_lookup.any_es -> uncore_cbox_1/event=0x34,umask=0x86/
>> Control descriptor is not initialized
>> ^Cunc_cbo_cache_lookup.any_es: 14361103 1853372468 1853372468
>> unc_cbo_cache_lookup.any_es: 14322188 1853360415 1853360415
>>
>>   Performance counter stats for 'system wide':
>>
>>          14,361,103      unc_cbo_cache_lookup.any_es
>>          14,322,188      unc_cbo_cache_lookup.any_es
>>
>>         1.853388227 seconds time elapsed
>>
> Ok, thanks. If I use events without a prefix, such as perf stat -e clockticks sleep 1, will this also work?

In this case, yes - it would work for uncore_cbox_0/clockticks/ and 
uncore_cbox_1/clockticks/

But you need to be careful to here - if another PMU has same event name, 
then it might also match.

Thanks,
John