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Date: Tue, 20 Jul 2021 09:45:39 -0600
From: Mathieu Poirier <mathieu.poirier@...aro.org>
To: James Clark <james.clark@....com>
Cc: acme@...nel.org, coresight@...ts.linaro.org, leo.yan@...aro.org,
al.grant@....com, branislav.rankov@....com, suzuki.poulose@....com,
anshuman.khandual@....com, Mike Leach <mike.leach@...aro.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...hat.com>,
Namhyung Kim <namhyung@...nel.org>,
John Garry <john.garry@...wei.com>,
Will Deacon <will@...nel.org>,
linux-arm-kernel@...ts.infradead.org,
linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/6] perf cs-etm: Pass unformatted flag to decoder
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@....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?
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
>
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