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Message-ID: <20210415194608.GA937505@xps15>
Date: Thu, 15 Apr 2021 13:46:08 -0600
From: Mathieu Poirier <mathieu.poirier@...aro.org>
To: James Clark <james.clark@....com>
Cc: coresight@...ts.linaro.org, al.grant@....com,
branislav.rankov@....com, denik@...omium.org,
suzuki.poulose@....com, Mike Leach <mike.leach@...aro.org>,
Leo Yan <leo.yan@...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 1/2] perf cs-etm: Refactor timestamp variable names
On Wed, Apr 14, 2021 at 05:39:18PM +0300, James Clark wrote:
> Remove ambiguity in variable names relating to timestamps.
> A later commit will save the sample kernel timestamp in one
> of the etm structs, so name all elements appropriately to
> avoid confusion.
>
> This is also removes some ambiguity arising from the fact
> that the --timestamp argument to perf record refers to
> sample kernel timestamps, and the /timestamp/ event modifier
> refers to etm timestamps, so the term is overloaded.
>
> Signed-off-by: James Clark <james.clark@....com>
> ---
> .../perf/util/cs-etm-decoder/cs-etm-decoder.c | 18 ++++----
> tools/perf/util/cs-etm.c | 42 +++++++++----------
> tools/perf/util/cs-etm.h | 4 +-
> 3 files changed, 31 insertions(+), 33 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 059bcec3f651..055cb93eca59 100644
> --- a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
> +++ b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
> @@ -276,13 +276,13 @@ cs_etm_decoder__do_soft_timestamp(struct cs_etm_queue *etmq,
> const uint8_t trace_chan_id)
> {
> /* No timestamp packet has been received, nothing to do */
> - if (!packet_queue->timestamp)
> + if (!packet_queue->etm_timestamp)
> return OCSD_RESP_CONT;
>
> - packet_queue->timestamp = packet_queue->next_timestamp;
> + packet_queue->etm_timestamp = packet_queue->next_etm_timestamp;
>
> /* Estimate the timestamp for the next range packet */
> - packet_queue->next_timestamp += packet_queue->instr_count;
> + packet_queue->next_etm_timestamp += packet_queue->instr_count;
> packet_queue->instr_count = 0;
>
> /* Tell the front end which traceid_queue needs attention */
> @@ -308,8 +308,8 @@ cs_etm_decoder__do_hard_timestamp(struct cs_etm_queue *etmq,
> * Function do_soft_timestamp() will report the value to the front end,
> * hence asking the decoder to keep decoding rather than stopping.
> */
> - if (packet_queue->timestamp) {
> - packet_queue->next_timestamp = elem->timestamp;
> + if (packet_queue->etm_timestamp) {
> + packet_queue->next_etm_timestamp = elem->timestamp;
> return OCSD_RESP_CONT;
> }
>
> @@ -320,8 +320,8 @@ cs_etm_decoder__do_hard_timestamp(struct cs_etm_queue *etmq,
> * which instructions started by subtracting the number of instructions
> * executed to the timestamp.
> */
> - packet_queue->timestamp = elem->timestamp - packet_queue->instr_count;
> - packet_queue->next_timestamp = elem->timestamp;
> + packet_queue->etm_timestamp = elem->timestamp - packet_queue->instr_count;
> + packet_queue->next_etm_timestamp = elem->timestamp;
> packet_queue->instr_count = 0;
>
> /* Tell the front end which traceid_queue needs attention */
> @@ -334,8 +334,8 @@ cs_etm_decoder__do_hard_timestamp(struct cs_etm_queue *etmq,
> static void
> cs_etm_decoder__reset_timestamp(struct cs_etm_packet_queue *packet_queue)
> {
> - packet_queue->timestamp = 0;
> - packet_queue->next_timestamp = 0;
> + packet_queue->etm_timestamp = 0;
> + packet_queue->next_etm_timestamp = 0;
> packet_queue->instr_count = 0;
> }
>
> diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
> index 7e63e7dedc33..c25da2ffa8f3 100644
> --- a/tools/perf/util/cs-etm.c
> +++ b/tools/perf/util/cs-etm.c
> @@ -38,8 +38,6 @@
> #include <tools/libc_compat.h>
> #include "util/synthetic-events.h"
>
> -#define MAX_TIMESTAMP (~0ULL)
> -
> struct cs_etm_auxtrace {
> struct auxtrace auxtrace;
> struct auxtrace_queues queues;
> @@ -86,7 +84,7 @@ struct cs_etm_queue {
> struct cs_etm_decoder *decoder;
> struct auxtrace_buffer *buffer;
> unsigned int queue_nr;
> - u8 pending_timestamp;
> + u8 pending_timestamp_chan_id;
> u64 offset;
> const unsigned char *buf;
> size_t buf_len, buf_used;
> @@ -208,7 +206,7 @@ void cs_etm__etmq_set_traceid_queue_timestamp(struct cs_etm_queue *etmq,
> * be more than one channel per cs_etm_queue, we need to specify
> * what traceID queue needs servicing.
> */
> - etmq->pending_timestamp = trace_chan_id;
> + etmq->pending_timestamp_chan_id = trace_chan_id;
> }
>
> static u64 cs_etm__etmq_get_timestamp(struct cs_etm_queue *etmq,
> @@ -216,22 +214,22 @@ static u64 cs_etm__etmq_get_timestamp(struct cs_etm_queue *etmq,
> {
> struct cs_etm_packet_queue *packet_queue;
>
> - if (!etmq->pending_timestamp)
> + if (!etmq->pending_timestamp_chan_id)
> return 0;
>
> if (trace_chan_id)
> - *trace_chan_id = etmq->pending_timestamp;
> + *trace_chan_id = etmq->pending_timestamp_chan_id;
>
> packet_queue = cs_etm__etmq_get_packet_queue(etmq,
> - etmq->pending_timestamp);
> + etmq->pending_timestamp_chan_id);
> if (!packet_queue)
> return 0;
>
> /* Acknowledge pending status */
> - etmq->pending_timestamp = 0;
> + etmq->pending_timestamp_chan_id = 0;
>
> /* See function cs_etm_decoder__do_{hard|soft}_timestamp() */
> - return packet_queue->timestamp;
> + return packet_queue->etm_timestamp;
> }
>
> static void cs_etm__clear_packet_queue(struct cs_etm_packet_queue *queue)
> @@ -814,7 +812,7 @@ static int cs_etm__setup_queue(struct cs_etm_auxtrace *etm,
> int ret = 0;
> unsigned int cs_queue_nr;
> u8 trace_chan_id;
> - u64 timestamp;
> + u64 etm_timestamp;
> struct cs_etm_queue *etmq = queue->priv;
>
> if (list_empty(&queue->head) || etmq)
> @@ -854,7 +852,7 @@ static int cs_etm__setup_queue(struct cs_etm_auxtrace *etm,
>
> /*
> * Run decoder on the trace block. The decoder will stop when
> - * encountering a timestamp, a full packet queue or the end of
> + * encountering an ETM timestamp, a full packet queue or the end of
> * trace for that block.
> */
> ret = cs_etm__decode_data_block(etmq);
> @@ -865,10 +863,10 @@ static int cs_etm__setup_queue(struct cs_etm_auxtrace *etm,
> * Function cs_etm_decoder__do_{hard|soft}_timestamp() does all
> * the timestamp calculation for us.
> */
> - timestamp = cs_etm__etmq_get_timestamp(etmq, &trace_chan_id);
> + etm_timestamp = cs_etm__etmq_get_timestamp(etmq, &trace_chan_id);
>
> /* We found a timestamp, no need to continue. */
> - if (timestamp)
> + if (etm_timestamp)
> break;
>
> /*
> @@ -892,7 +890,7 @@ static int cs_etm__setup_queue(struct cs_etm_auxtrace *etm,
> * queue and will be processed in cs_etm__process_queues().
> */
> cs_queue_nr = TO_CS_QUEUE_NR(queue_nr, trace_chan_id);
> - ret = auxtrace_heap__add(&etm->heap, cs_queue_nr, timestamp);
> + ret = auxtrace_heap__add(&etm->heap, cs_queue_nr, etm_timestamp);
> out:
> return ret;
> }
> @@ -2221,7 +2219,7 @@ static int cs_etm__process_queues(struct cs_etm_auxtrace *etm)
> int ret = 0;
> unsigned int cs_queue_nr, queue_nr;
> u8 trace_chan_id;
> - u64 timestamp;
> + u64 etm_timestamp;
> struct auxtrace_queue *queue;
> struct cs_etm_queue *etmq;
> struct cs_etm_traceid_queue *tidq;
> @@ -2283,9 +2281,9 @@ static int cs_etm__process_queues(struct cs_etm_auxtrace *etm)
> if (ret)
> goto out;
>
> - timestamp = cs_etm__etmq_get_timestamp(etmq, &trace_chan_id);
> + etm_timestamp = cs_etm__etmq_get_timestamp(etmq, &trace_chan_id);
>
> - if (!timestamp) {
> + if (!etm_timestamp) {
> /*
> * Function cs_etm__decode_data_block() returns when
> * there is no more traces to decode in the current
> @@ -2308,7 +2306,7 @@ static int cs_etm__process_queues(struct cs_etm_auxtrace *etm)
> * this queue/traceID.
> */
> cs_queue_nr = TO_CS_QUEUE_NR(queue_nr, trace_chan_id);
> - ret = auxtrace_heap__add(&etm->heap, cs_queue_nr, timestamp);
> + ret = auxtrace_heap__add(&etm->heap, cs_queue_nr, etm_timestamp);
> }
>
> out:
> @@ -2380,7 +2378,7 @@ static int cs_etm__process_event(struct perf_session *session,
> struct perf_tool *tool)
> {
> int err = 0;
> - u64 timestamp;
> + u64 sample_kernel_timestamp;
> struct cs_etm_auxtrace *etm = container_of(session->auxtrace,
> struct cs_etm_auxtrace,
> auxtrace);
> @@ -2394,11 +2392,11 @@ static int cs_etm__process_event(struct perf_session *session,
> }
>
> if (sample->time && (sample->time != (u64) -1))
> - timestamp = sample->time;
> + sample_kernel_timestamp = sample->time;
> else
> - timestamp = 0;
> + sample_kernel_timestamp = 0;
>
> - if (timestamp || etm->timeless_decoding) {
> + if (sample_kernel_timestamp || etm->timeless_decoding) {
> err = cs_etm__update_queues(etm);
> if (err)
> return err;
> diff --git a/tools/perf/util/cs-etm.h b/tools/perf/util/cs-etm.h
> index 36428918411e..b300f6fa19cc 100644
> --- a/tools/perf/util/cs-etm.h
> +++ b/tools/perf/util/cs-etm.h
> @@ -171,8 +171,8 @@ struct cs_etm_packet_queue {
> u32 head;
> u32 tail;
> u32 instr_count;
> - u64 timestamp;
> - u64 next_timestamp;
> + u64 etm_timestamp;
> + u64 next_etm_timestamp;
I find the "etm" part confusing since timestamps are generated by a specific CS
component, not the ETM itself. As such I think it should be "cs_timestamp" and
"next_cs_timestamp". But this is just a naming convention and won't press the
case further if you feel strongly about it.
Otherwise I think this renaming exercise is worth it.
With or without the above:
Reviewed-by: Mathieu Poirier <mathieu.poirier@...aro.org>
> struct cs_etm_packet packet_buffer[CS_ETM_PACKET_MAX_BUFFER];
> };
>
> --
> 2.28.0
>
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