Re: [PATCH] perf cs-etm: Add support for coresight trace for any range of CPUs

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

On 20/04/2023 10:43, James Clark wrote:
> 
> 
> On 19/04/2023 18:21, Ganapatrao Kulkarni wrote:
>> The current implementation supports coresight trace for a range of
>> CPUs, if the first CPU is CPU0.
>>
>> Adding changes to enable coresight trace for any range of CPUs by
>> decoding the first CPU also from the header.
>> Later, first CPU id is used instead of CPU0 across the decoder functions.
>>
>> Signed-off-by: Ganapatrao Kulkarni <gankulkarni@os.amperecomputing.com>
>> ---
>>  .../perf/util/cs-etm-decoder/cs-etm-decoder.c |  4 +-
>>  .../perf/util/cs-etm-decoder/cs-etm-decoder.h |  3 +-
>>  tools/perf/util/cs-etm.c                      | 62 ++++++++++++-------
>>  3 files changed, 42 insertions(+), 27 deletions(-)
>>
>> diff --git a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
>> index 82a27ab90c8b..41ab299b643b 100644
>> --- a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
>> +++ b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
>> @@ -724,7 +724,7 @@ cs_etm_decoder__create_etm_decoder(struct cs_etm_decoder_params *d_params,
>>  }
>>  
>>  struct cs_etm_decoder *
>> -cs_etm_decoder__new(int decoders, struct cs_etm_decoder_params *d_params,
>> +cs_etm_decoder__new(int first_decoder, int decoders, struct cs_etm_decoder_params *d_params,
>>  		    struct cs_etm_trace_params t_params[])
>>  {
>>  	struct cs_etm_decoder *decoder;
>> @@ -769,7 +769,7 @@ cs_etm_decoder__new(int decoders, struct cs_etm_decoder_params *d_params,
>>  	/* init raw frame logging if required */
>>  	cs_etm_decoder__init_raw_frame_logging(d_params, decoder);
>>  
>> -	for (i = 0; i < decoders; i++) {
>> +	for (i = first_decoder; i < decoders; i++) {
>>  		ret = cs_etm_decoder__create_etm_decoder(d_params,
>>  							 &t_params[i],
>>  							 decoder);
>> diff --git a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.h b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.h
>> index 92a855fbe5b8..b06193fc75b4 100644
>> --- a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.h
>> +++ b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.h
>> @@ -90,7 +90,8 @@ int cs_etm_decoder__process_data_block(struct cs_etm_decoder *decoder,
>>  				       size_t len, size_t *consumed);
>>  
>>  struct cs_etm_decoder *
>> -cs_etm_decoder__new(int num_cpu,
>> +cs_etm_decoder__new(int first_decoder,
>> +		    int decoders,
>>  		    struct cs_etm_decoder_params *d_params,
>>  		    struct cs_etm_trace_params t_params[]);
>>  
>> diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
>> index 94e2d02009eb..2619513ae088 100644
>> --- a/tools/perf/util/cs-etm.c
>> +++ b/tools/perf/util/cs-etm.c
>> @@ -55,6 +55,8 @@ struct cs_etm_auxtrace {
>>  	u8 has_virtual_ts; /* Virtual/Kernel timestamps in the trace. */
>>  
>>  	int num_cpu;
>> +	int first_cpu;
>> +	int last_cpu;
>>  	u64 latest_kernel_timestamp;
>>  	u32 auxtrace_type;
>>  	u64 branches_sample_type;
>> @@ -638,14 +640,13 @@ static void cs_etm__set_trace_param_ete(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,
>> -				     int decoders)
>> +				     struct cs_etm_auxtrace *etm)
>>  {
>>  	int i;
>>  	u32 etmidr;
>>  	u64 architecture;
>>  
>> -	for (i = 0; i < decoders; i++) {
>> +	for (i = etm->first_cpu; i < etm->last_cpu; i++) {
>>  		architecture = etm->metadata[i][CS_ETM_MAGIC];
>>  
>>  		switch (architecture) {
>> @@ -817,7 +818,7 @@ static void cs_etm__free(struct perf_session *session)
>>  	/* Then the RB tree itself */
>>  	intlist__delete(traceid_list);
>>  
>> -	for (i = 0; i < aux->num_cpu; i++)
>> +	for (i = aux->first_cpu; i < aux->last_cpu; i++)
>>  		zfree(&aux->metadata[i]);
>>  
>>  	thread__zput(aux->unknown_thread);
>> @@ -921,7 +922,8 @@ static struct cs_etm_queue *cs_etm__alloc_queue(struct cs_etm_auxtrace *etm,
>>  	 * Each queue can only contain data from one CPU when unformatted, so only one decoder is
>>  	 * needed.
>>  	 */
>> -	int decoders = formatted ? etm->num_cpu : 1;
>> +	int first_decoder = formatted ? etm->first_cpu : 0;
>> +	int decoders = first_decoder + (formatted ? etm->num_cpu : 1);
>>  
>>  	etmq = zalloc(sizeof(*etmq));
>>  	if (!etmq)
>> @@ -937,7 +939,7 @@ static struct cs_etm_queue *cs_etm__alloc_queue(struct cs_etm_auxtrace *etm,
>>  	if (!t_params)
>>  		goto out_free;
>>  
>> -	if (cs_etm__init_trace_params(t_params, etm, decoders))
>> +	if (cs_etm__init_trace_params(t_params, etm))
>>  		goto out_free;
>>  
>>  	/* Set decoder parameters to decode trace packets */
>> @@ -947,8 +949,7 @@ static struct cs_etm_queue *cs_etm__alloc_queue(struct cs_etm_auxtrace *etm,
>>  					formatted))
>>  		goto out_free;
>>  
>> -	etmq->decoder = cs_etm_decoder__new(decoders, &d_params,
>> -					    t_params);
>> +	etmq->decoder = cs_etm_decoder__new(first_decoder, decoders, &d_params, t_params);
>>  
>>  	if (!etmq->decoder)
>>  		goto out_free;
>> @@ -2959,11 +2960,11 @@ static int cs_etm__queue_aux_records(struct perf_session *session)
>>   * Loop through the ETMs and complain if we find at least one where ts_source != 1 (virtual
>>   * timestamps).
>>   */
>> -static bool cs_etm__has_virtual_ts(u64 **metadata, int num_cpu)
>> +static bool cs_etm__has_virtual_ts(u64 **metadata, struct cs_etm_auxtrace *etm)
>>  {
>>  	int j;
>>  
>> -	for (j = 0; j < num_cpu; j++) {
>> +	for (j = etm->first_cpu; j < etm->last_cpu; j++) {
>>  		switch (metadata[j][CS_ETM_MAGIC]) {
>>  		case __perf_cs_etmv4_magic:
>>  			if (HAS_PARAM(j, ETMV4, TS_SOURCE) || metadata[j][CS_ETMV4_TS_SOURCE] != 1)
>> @@ -2982,13 +2983,14 @@ static bool cs_etm__has_virtual_ts(u64 **metadata, int num_cpu)
>>  }
>>  
>>  /* map trace ids to correct metadata block, from information in metadata */
>> -static int cs_etm__map_trace_ids_metadata(int num_cpu, u64 **metadata)
>> +static int cs_etm__map_trace_ids_metadata(struct cs_etm_auxtrace *etm)
>>  {
>>  	u64 cs_etm_magic;
>> +	u64 **metadata = etm->metadata;
>>  	u8 trace_chan_id;
>>  	int i, err;
>>  
>> -	for (i = 0; i < num_cpu; i++) {
>> +	for (i = etm->first_cpu; i < etm->last_cpu; i++) {
>>  		cs_etm_magic = metadata[i][CS_ETM_MAGIC];
>>  		switch (cs_etm_magic) {
>>  		case __perf_cs_etmv3_magic:
>> @@ -3015,12 +3017,13 @@ static int cs_etm__map_trace_ids_metadata(int num_cpu, u64 **metadata)
>>   * If we found AUX_HW_ID packets, then set any metadata marked as unused to the
>>   * unused value to reduce the number of unneeded decoders created.
>>   */
>> -static int cs_etm__clear_unused_trace_ids_metadata(int num_cpu, u64 **metadata)
>> +static int cs_etm__clear_unused_trace_ids_metadata(struct cs_etm_auxtrace *etm)
>>  {
>>  	u64 cs_etm_magic;
>> +	u64 **metadata = etm->metadata;
>>  	int i;
>>  
>> -	for (i = 0; i < num_cpu; i++) {
>> +	for (i = etm->first_cpu; i < etm->last_cpu; i++) {
>>  		cs_etm_magic = metadata[i][CS_ETM_MAGIC];
>>  		switch (cs_etm_magic) {
>>  		case __perf_cs_etmv3_magic:
>> @@ -3049,7 +3052,7 @@ int cs_etm__process_auxtrace_info_full(union perf_event *event,
>>  	int event_header_size = sizeof(struct perf_event_header);
>>  	int total_size = auxtrace_info->header.size;
>>  	int priv_size = 0;
>> -	int num_cpu;
>> +	int num_cpu, first_cpu = 0, last_cpu;
>>  	int err = 0;
>>  	int aux_hw_id_found;
>>  	int i, j;
>> @@ -3068,22 +3071,31 @@ int cs_etm__process_auxtrace_info_full(union perf_event *event,
>>  	/* First the global part */
>>  	ptr = (u64 *) auxtrace_info->priv;
>>  	num_cpu = ptr[CS_PMU_TYPE_CPUS] & 0xffffffff;
>> -	metadata = zalloc(sizeof(*metadata) * num_cpu);
>> +
>> +	/* Start parsing after the common part of the header */
>> +	i = CS_HEADER_VERSION_MAX;
>> +
>> +	/*Get CPU id of first event */
>> +	first_cpu = ptr[i + CS_ETM_CPU];
>> +	last_cpu = first_cpu + num_cpu;
>> +
>> +	if (first_cpu > cpu__max_cpu().cpu ||
>> +			last_cpu > cpu__max_cpu().cpu)
>> +		return -EINVAL;
>> +
>> +	metadata = zalloc(sizeof(*metadata) * last_cpu);
> 
> Hi Ganapatrao,
> 
> I think I see what the problem is, but I'm wondering if a better fix
> would be to further decouple the CPU ID from the index in the array.
> 
> With your change it's not clear what happens with sparse recordings, for
> example 'perf record -e cs_etm// -C 1,3,5'. And it seems like there is
> some wastage in the zalloc here for example if only CPU 256 is traced
> then we'd still make 256 decoders but 255 of them would be unused?
> 
> I tried to test sparse recordings, but your change doesn't apply to the
> latest coresight/next branch. I did notice that 'perf report -D' doesn't
> work with them on coresight/next (it just quits), but I couldn't see if
> that's fixed with your change.
> 
> Would a better fix not be to keep the metadata loops from 0-N and
> instead save the CPU ID in cs_etm_decoder_params or the decoder. That
> way it would support both sparse and not starting from 0 cases? I think
> the code would be better if it's worded like "i < recorded_cpus" rather
> than "i < cpu" to make it clear that i isn't actually the CPU ID it's
> just an index.
> 
> Also a new test for this scenario would probably be a good idea.
> 
> Thanks
> James
> 

BTW for the test, I'm currently working on something where I've added
something like this to test_arm_coresight.sh:


  arm_cs_etm_basic_test() {
	echo "Recording trace with $@"
	perf record -o ${perfdata} "$@" -- ls > /dev/null 2>&1

	perf_script_branch_samples ls &&
	perf_report_branch_samples ls &&
	perf_report_instruction_samples ls

	err=$?
	arm_cs_report "CoreSight basic testing with %@" $err
  }

  # Test all combinations of per-thread, system-wide and normal mode with
  # and without timestamps
  arm_cs_etm_basic_test -e cs_etm/timestamp=0/ --per-thread
  arm_cs_etm_basic_test -e cs_etm/timestamp=1/ --per-thread
  arm_cs_etm_basic_test -e cs_etm/timestamp=0/ -a
  arm_cs_etm_basic_test -e cs_etm/timestamp=1/ -a
  arm_cs_etm_basic_test -e cs_etm/timestamp=0/
  arm_cs_etm_basic_test -e cs_etm/timestamp=1/

I think you should be able to add this to cover your cases as well:

  # Test non-zero indexed and sparse CPU lists
  arm_cs_etm_basic_test -e cs_etm// -C 1,2
  arm_cs_etm_basic_test -e cs_etm// -C 0,2

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