Re: [PATCH V3 20/37] perf script: Add 'synth' event type for synthesized events

[Adrian Hunter <adrian.hunter@intel.com>]

On 06/21/2017 04:51 PM, Arnaldo Carvalho de Melo wrote:
> Em Wed, Jun 21, 2017 at 01:17:19PM +0300, Adrian Hunter escreveu:
>> +++ b/tools/perf/util/event.h
>> @@ -252,6 +252,9 @@ enum auxtrace_error_type {
>>        PERF_AUXTRACE_ERROR_MAX
>> };
> 
>> +/* Attribute type for custom synthesized events */
>> +#define PERF_TYPE_SYNTH		3000000000
> 
> Why don't you make it PERF_TYPE_MAX and bump PERF_TYPE_MAX by one? I.e.
> this way we have what can be in attr.type in a nice enumeration, can
> validate it more easily (attr.type < PERF_TYPE_MAX) and will not need to 
> do those conversions to/from OUTPUT_TYPE_/PERF_TYPE_).

PERF_TYPE_ is dynamically allocated above PERF_TYPE_MAX for PMUs.  Presently
perf_pmu_register() calls idr_alloc() with end=0 which limits the allocation
to INT_MAX.

> Peter: now its not the PERF_RECORD_ namespace that userspaces want a
> chunk of, its PERF_TYPE_, which so far has been pretty stable, grabing
> _one_ for event synthesizing things like Intel PT (and ARM's coresight,
> I think) directly at include/uapi/linux/perf_event.h's perf_type_id enum
> looks cleaner, no?