[RFC PATCH v3] perf cs-etm: Split Coresight decode by aux records

[James Clark]

On 27/05/2021 18:37, Mathieu Poirier wrote:
> On Thu, 27 May 2021 at 07:46, James Clark <james.clark at arm.com> wrote:
>>
>>
>>
>> On 27/05/2021 13:42, James Clark wrote:
>>> Populate the auxtrace queues using AUX records rather than whole
>>> auxtrace buffers.
>>>
>> ...
>>> Snapshot mode still needs to be tested.
>>>
>>
>> Snapshot mode is also working, but needs the following patch applied to reverse aux_offset
>> from the end of the buffer to the beginning:
> 
> It might be better to send another revision with this patch included
> in to make sure everyone is looking at (and testing) the same thing.

I've sent v4 with it applied. There was actually a mistake which broke the normal mode,
so it was a good idea to apply it.

> 
>>
>> diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
>> index 5d6c03488187..9db556e14dfa 100644
>> --- a/tools/perf/util/cs-etm.c
>> +++ b/tools/perf/util/cs-etm.c
>> @@ -2700,6 +2700,7 @@ static int cs_etm__queue_aux_fragment(struct perf_session *session,
>>         struct perf_record_auxtrace *auxtrace_event;
>>         union perf_event auxtrace_fragment;
>>         bool matchesCpuPid;
>> +       __u64 aux_offset;
>>         struct cs_etm_auxtrace *etm = container_of(session->auxtrace,
>>                                                    struct cs_etm_auxtrace,
>>                                                    auxtrace);
>> @@ -2730,19 +2731,26 @@ static int cs_etm__queue_aux_fragment(struct perf_session *session,
>>         else
>>                 matchesCpuPid = auxtrace_event->cpu == sample->cpu;
>>
>> +       /*
>> +        * In snapshot/overwrite mode, the head points to the end of the buffer so aux_offset needs
>> +        * to have the size subtracted so it points to the beginning as in normal mode.
>> +        */
>> +       if (aux_event->flags && PERF_AUX_FLAG_OVERWRITE)
>> +               aux_offset = aux_event->aux_offset - aux_event->aux_size;
>> +       else
>> +               aux_offset = aux_event->aux_offset;
>> +
>>         if (matchesCpuPid &&
>> -           aux_event->aux_offset >= auxtrace_event->offset &&
>> -           aux_event->aux_offset + aux_event->aux_size <=
>> -                       auxtrace_event->offset + auxtrace_event->size) {
>> +           aux_offset >= auxtrace_event->offset &&
>> +           aux_offset + aux_event->aux_size <= auxtrace_event->offset + auxtrace_event->size) {
>>                 /*
>>                  * If this AUX event was inside this buffer somewhere, create a new auxtrace event
>>                  * based on the sizes of the aux event, and queue that fragment.
>>                  */
>>                 auxtrace_fragment.auxtrace = *auxtrace_event;
>>                 auxtrace_fragment.auxtrace.size = aux_event->aux_size;
>> -               auxtrace_fragment.auxtrace.offset = aux_event->aux_offset;
>> -               file_offset += aux_event->aux_offset - auxtrace_event->offset +
>> -                               auxtrace_event->header.size;
>> +               auxtrace_fragment.auxtrace.offset = aux_offset;
>> +               file_offset += aux_offset - auxtrace_event->offset + auxtrace_event->header.size;
>>                 return auxtrace_queues__add_event(&etm->queues,
>>                                                session,
>>                                                &auxtrace_fragment,
>>
>>