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

[Mathieu Poirier]

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@xxxxxxx>
> ---
>  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?

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
>