Re: [PATCH 6/6] perf cs-etm: Pass unformatted flag to decoder

[James Clark <james.clark@arm.com>]

On 20/07/2021 16:45, Mathieu Poirier wrote:
> On Tue, Jul 13, 2021 at 04:40:08PM +0100, James Clark wrote:
>> The TRBE (Trace Buffer Extension) feature allows a separate trace buffer
>> for each trace source, therefore the trace wouldn't need to be
>> formatted. The driver was introduced in commit 3fbf7f011f24
>> ("coresight: sink: Add TRBE driver").
>>
>> The formatted/unformatted mode is encoded in one of the flags of the
>> AUX record. The first AUX record encountered for each event is used to
>> determine the mode, and this will persist for the remaining trace that
>> is either decoded or dumped.
>>
>> Signed-off-by: James Clark <james.clark@arm.com>
>> ---
>>  tools/perf/util/cs-etm.c | 42 +++++++++++++++++++++++++++-------------
>>  1 file changed, 29 insertions(+), 13 deletions(-)
>>
>> diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
>> index 760050ea936d..62769a84a53f 100644
>> --- a/tools/perf/util/cs-etm.c
>> +++ b/tools/perf/util/cs-etm.c
>> @@ -461,13 +461,14 @@ static void cs_etm__set_trace_param_etmv4(struct cs_etm_trace_params *t_params,
>>  }
>>  
>>  static int cs_etm__init_trace_params(struct cs_etm_trace_params *t_params,
>> -				     struct cs_etm_auxtrace *etm)
>> +				     struct cs_etm_auxtrace *etm,
>> +				     int decoders_per_cpu)
>>  {
>>  	int i;
>>  	u32 etmidr;
>>  	u64 architecture;
>>  
>> -	for (i = 0; i < etm->num_cpu; i++) {
>> +	for (i = 0; i < decoders_per_cpu; i++) {
>>  		architecture = etm->metadata[i][CS_ETM_MAGIC];
>>  
>>  		switch (architecture) {
>> @@ -488,7 +489,8 @@ static int cs_etm__init_trace_params(struct cs_etm_trace_params *t_params,
>>  
>>  static int cs_etm__init_decoder_params(struct cs_etm_decoder_params *d_params,
>>  				       struct cs_etm_queue *etmq,
>> -				       enum cs_etm_decoder_operation mode)
>> +				       enum cs_etm_decoder_operation mode,
>> +				       bool formatted)
>>  {
>>  	int ret = -EINVAL;
>>  
>> @@ -498,7 +500,7 @@ static int cs_etm__init_decoder_params(struct cs_etm_decoder_params *d_params,
>>  	d_params->packet_printer = cs_etm__packet_dump;
>>  	d_params->operation = mode;
>>  	d_params->data = etmq;
>> -	d_params->formatted = true;
>> +	d_params->formatted = formatted;
>>  	d_params->fsyncs = false;
>>  	d_params->hsyncs = false;
>>  	d_params->frame_aligned = true;
>> @@ -720,11 +722,13 @@ static u32 cs_etm__mem_access(struct cs_etm_queue *etmq, u8 trace_chan_id,
>>  	return len;
>>  }
>>  
>> -static struct cs_etm_queue *cs_etm__alloc_queue(struct cs_etm_auxtrace *etm)
>> +static struct cs_etm_queue *cs_etm__alloc_queue(struct cs_etm_auxtrace *etm,
>> +						bool formatted)
>>  {
>>  	struct cs_etm_decoder_params d_params;
>>  	struct cs_etm_trace_params  *t_params = NULL;
>>  	struct cs_etm_queue *etmq;
>> +	int decoders_per_cpu = formatted ? etm->num_cpu : 1;
> 
> I really tripped on the name "decoders_per_cpu", to a point where I had to
> review the current code before looking at this patch.  I find the "_per_cpu"
> part especially puzzling.  In the end the variable determines the amount of
> decoders to instantiate for a specific queue...  
> 
> Couldn't it be just "decoders"?  Or maybe it just needs a little comment to
> disambiguate things?
> 

Yeah I think just decoders will be good if I add a comment explaining why there is
a difference with formatted vs unformatted. I will re-submit with the change.

Thanks for the reviews.

James

> Thanks,
> Mathieu
> 
>>  
>>  	etmq = zalloc(sizeof(*etmq));
>>  	if (!etmq)
>> @@ -735,21 +739,23 @@ static struct cs_etm_queue *cs_etm__alloc_queue(struct cs_etm_auxtrace *etm)
>>  		goto out_free;
>>  
>>  	/* Use metadata to fill in trace parameters for trace decoder */
>> -	t_params = zalloc(sizeof(*t_params) * etm->num_cpu);
>> +	t_params = zalloc(sizeof(*t_params) * decoders_per_cpu);
>>  
>>  	if (!t_params)
>>  		goto out_free;
>>  
>> -	if (cs_etm__init_trace_params(t_params, etm))
>> +	if (cs_etm__init_trace_params(t_params, etm, decoders_per_cpu))
>>  		goto out_free;
>>  
>>  	/* Set decoder parameters to decode trace packets */
>>  	if (cs_etm__init_decoder_params(&d_params, etmq,
>>  					dump_trace ? CS_ETM_OPERATION_PRINT :
>> -						     CS_ETM_OPERATION_DECODE))
>> +						     CS_ETM_OPERATION_DECODE,
>> +					formatted))
>>  		goto out_free;
>>  
>> -	etmq->decoder = cs_etm_decoder__new(etm->num_cpu, &d_params, t_params);
>> +	etmq->decoder = cs_etm_decoder__new(decoders_per_cpu, &d_params,
>> +					    t_params);
>>  
>>  	if (!etmq->decoder)
>>  		goto out_free;
>> @@ -777,14 +783,15 @@ static struct cs_etm_queue *cs_etm__alloc_queue(struct cs_etm_auxtrace *etm)
>>  
>>  static int cs_etm__setup_queue(struct cs_etm_auxtrace *etm,
>>  			       struct auxtrace_queue *queue,
>> -			       unsigned int queue_nr)
>> +			       unsigned int queue_nr,
>> +			       bool formatted)
>>  {
>>  	struct cs_etm_queue *etmq = queue->priv;
>>  
>>  	if (list_empty(&queue->head) || etmq)
>>  		return 0;
>>  
>> -	etmq = cs_etm__alloc_queue(etm);
>> +	etmq = cs_etm__alloc_queue(etm, formatted);
>>  
>>  	if (!etmq)
>>  		return -ENOMEM;
>> @@ -2430,8 +2437,14 @@ static int cs_etm__process_auxtrace_event(struct perf_session *session,
>>  		if (err)
>>  			return err;
>>  
>> +		/*
>> +		 * Knowing if the trace is formatted or not requires a lookup of
>> +		 * the aux record so only works in non-piped mode where data is
>> +		 * queued in cs_etm__queue_aux_records(). Always assume
>> +		 * formatted in piped mode (true).
>> +		 */
>>  		err = cs_etm__setup_queue(etm, &etm->queues.queue_array[idx],
>> -					  idx);
>> +					  idx, true);
>>  		if (err)
>>  			return err;
>>  
>> @@ -2678,6 +2691,7 @@ static int cs_etm__queue_aux_fragment(struct perf_session *session, off_t file_o
>>  	union perf_event auxtrace_fragment;
>>  	__u64 aux_offset, aux_size;
>>  	__u32 idx;
>> +	bool formatted;
>>  
>>  	struct cs_etm_auxtrace *etm = container_of(session->auxtrace,
>>  						   struct cs_etm_auxtrace,
>> @@ -2745,7 +2759,9 @@ static int cs_etm__queue_aux_fragment(struct perf_session *session, off_t file_o
>>  			return err;
>>  
>>  		idx = auxtrace_event->idx;
>> -		return cs_etm__setup_queue(etm, &etm->queues.queue_array[idx], idx);
>> +		formatted = !(aux_event->flags & PERF_AUX_FLAG_CORESIGHT_FORMAT_RAW);
>> +		return cs_etm__setup_queue(etm, &etm->queues.queue_array[idx],
>> +					   idx, formatted);
>>  	}
>>  
>>  	/* Wasn't inside this buffer, but there were no parse errors. 1 == 'not found' */
>> -- 
>> 2.28.0
>>