Date:   Thu, 20 Apr 2023 17:17:54 +0530
From:   Ganapatrao Kulkarni <gankulkarni@...amperecomputing.com>
To:     James Clark <james.clark@....com>
Cc:     mathieu.poirier@...aro.org, acme@...nel.org,
        darren@...amperecomputing.com, scott@...amperecomputing.com,
        scclevenger@...amperecomputing.com, linux-kernel@...r.kernel.org,
        coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
        mike.leach@...aro.org, suzuki.poulose@....com
Subject: Re: [PATCH] perf cs-etm: Add support for coresight trace for any
 range of CPUs


Hi James,

On 20-04-2023 03:13 pm, 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@...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

This patch fixes for any range of CPUs.
Record with sparse list of CPUs will not work with current code still.

> 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.

My patch is rebased on 6.3-RC7 codebase with Mike's 3 perf patches 
related to dynamic id [1] support(queued for 6.4).

"perf report -D" works for me.

[1] https://www.spinics.net/lists/linux-perf-users/msg27452.html

> 
> 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

Yep, I though this initially, it got complicated due to for more 
for-loops. I will try again and post V2.

> 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.

Yes, makes sense to call it "recorded_cpus".

> 
> Also a new test for this scenario would probably be a good idea.
> 
> Thanks
> James
> 
Thanks,
Ganapat

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