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SubjectRe: [PATCH v2 16/17] perf tools: Add notion of time to decoding code
Em Fri, May 24, 2019 at 11:35:07AM -0600, Mathieu Poirier escreveu:
> This patch deals with timestamp packets received from the decoding library
> in order to give the front end packet processing loop a handle on the time
> instruction conveyed by range packets have been executed at.
>
> Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
> ---
> .../perf/util/cs-etm-decoder/cs-etm-decoder.c | 112 +++++++++++++++++-
> tools/perf/util/cs-etm.c | 19 +++
> tools/perf/util/cs-etm.h | 17 +++
> 3 files changed, 144 insertions(+), 4 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 ce85e52f989c..33e975c8d11b 100644
> --- a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
> +++ b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
> @@ -269,6 +269,76 @@ cs_etm_decoder__create_etm_packet_printer(struct cs_etm_trace_params *t_params,
> trace_config);
> }
>
> +static ocsd_datapath_resp_t
> +cs_etm_decoder__do_soft_timestamp(struct cs_etm_queue *etmq,
> + struct cs_etm_packet_queue *packet_queue,
> + const uint8_t trace_chan_id)
> +{
> + /* No timestamp packet has been received, nothing to do */
> + if (!packet_queue->timestamp)
> + return OCSD_RESP_CONT;
> +
> + packet_queue->timestamp = packet_queue->next_timestamp;
> +
> + /* Estimate the timestamp for the next range packet */
> + packet_queue->next_timestamp += packet_queue->instr_count;
> + packet_queue->instr_count = 0;
> +
> + /* Tell the front end which traceid_queue needs attention */
> + cs_etm__etmq_set_traceid_queue_timestamp(etmq, trace_chan_id);
> +
> + return OCSD_RESP_WAIT;
> +}
> +
> +static ocsd_datapath_resp_t
> +cs_etm_decoder__do_hard_timestamp(struct cs_etm_queue *etmq,
> + const ocsd_generic_trace_elem *elem,
> + const uint8_t trace_chan_id)
> +{
> + struct cs_etm_packet_queue *packet_queue;
> +
> + /* First get the packet queue for this traceID */
> + packet_queue = cs_etm__etmq_get_packet_queue(etmq, trace_chan_id);
> + if (!packet_queue)
> + return OCSD_RESP_FATAL_SYS_ERR;
> +
> + /*
> + * We've seen a timestamp packet before - simply record the new value.
> + * 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;
> + return OCSD_RESP_CONT;
> + }
> +
> + /*
> + * This is the first timestamp we've seen since the beginning of traces
> + * or a discontinuity. Since timestamps packets are generated *after*
> + * range packets have been generated, we need to estimate the time at
> + * which instructions started by substracting the number of instructions
> + * executed to the timestamp.
> + */
> + packet_queue->timestamp = elem->timestamp -
> + packet_queue->instr_count;

No need to break lines like that, in this case it even wouldn't pass the
width used for the comments right above it :-)

I'm fixing it up this time.

Something else, all the patches in this series, so far, needed to have
as the subject prefix "perf cs-etm: ...", not the generic one "perf
tools: ...". I'm fixing it up as well, no need to resend.

- Arnaldo

> + packet_queue->next_timestamp = elem->timestamp;
> + packet_queue->instr_count = 0;
> +
> + /* Tell the front end which traceid_queue needs attention */
> + cs_etm__etmq_set_traceid_queue_timestamp(etmq, trace_chan_id);
> +
> + /* Halt processing until we are being told to proceed */
> + return OCSD_RESP_WAIT;
> +}
> +
> +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->instr_count = 0;
> +}
> +
> static ocsd_datapath_resp_t
> cs_etm_decoder__buffer_packet(struct cs_etm_packet_queue *packet_queue,
> const u8 trace_chan_id,
> @@ -310,7 +380,8 @@ cs_etm_decoder__buffer_packet(struct cs_etm_packet_queue *packet_queue,
> }
>
> static ocsd_datapath_resp_t
> -cs_etm_decoder__buffer_range(struct cs_etm_packet_queue *packet_queue,
> +cs_etm_decoder__buffer_range(struct cs_etm_queue *etmq,
> + struct cs_etm_packet_queue *packet_queue,
> const ocsd_generic_trace_elem *elem,
> const uint8_t trace_chan_id)
> {
> @@ -365,6 +436,23 @@ cs_etm_decoder__buffer_range(struct cs_etm_packet_queue *packet_queue,
>
> packet->last_instr_size = elem->last_instr_sz;
>
> + /* per-thread scenario, no need to generate a timestamp */
> + if (cs_etm__etmq_is_timeless(etmq))
> + goto out;
> +
> + /*
> + * The packet queue is full and we haven't seen a timestamp (had we
> + * seen one the packet queue wouldn't be full). Let the front end
> + * deal with it.
> + */
> + if (ret == OCSD_RESP_WAIT)
> + goto out;
> +
> + packet_queue->instr_count += elem->num_instr_range;
> + /* Tell the front end we have a new timestamp to process */
> + ret = cs_etm_decoder__do_soft_timestamp(etmq, packet_queue,
> + trace_chan_id);
> +out:
> return ret;
> }
>
> @@ -372,6 +460,11 @@ static ocsd_datapath_resp_t
> cs_etm_decoder__buffer_discontinuity(struct cs_etm_packet_queue *queue,
> const uint8_t trace_chan_id)
> {
> + /*
> + * Something happened and who knows when we'll get new traces so
> + * reset time statistics.
> + */
> + cs_etm_decoder__reset_timestamp(queue);
> return cs_etm_decoder__buffer_packet(queue, trace_chan_id,
> CS_ETM_DISCONTINUITY);
> }
> @@ -404,6 +497,7 @@ cs_etm_decoder__buffer_exception_ret(struct cs_etm_packet_queue *queue,
>
> static ocsd_datapath_resp_t
> cs_etm_decoder__set_tid(struct cs_etm_queue *etmq,
> + struct cs_etm_packet_queue *packet_queue,
> const ocsd_generic_trace_elem *elem,
> const uint8_t trace_chan_id)
> {
> @@ -417,6 +511,12 @@ cs_etm_decoder__set_tid(struct cs_etm_queue *etmq,
> if (cs_etm__etmq_set_tid(etmq, tid, trace_chan_id))
> return OCSD_RESP_FATAL_SYS_ERR;
>
> + /*
> + * A timestamp is generated after a PE_CONTEXT element so make sure
> + * to rely on that coming one.
> + */
> + cs_etm_decoder__reset_timestamp(packet_queue);
> +
> return OCSD_RESP_CONT;
> }
>
> @@ -446,7 +546,7 @@ static ocsd_datapath_resp_t cs_etm_decoder__gen_trace_elem_printer(
> trace_chan_id);
> break;
> case OCSD_GEN_TRC_ELEM_INSTR_RANGE:
> - resp = cs_etm_decoder__buffer_range(packet_queue, elem,
> + resp = cs_etm_decoder__buffer_range(etmq, packet_queue, elem,
> trace_chan_id);
> break;
> case OCSD_GEN_TRC_ELEM_EXCEPTION:
> @@ -457,11 +557,15 @@ static ocsd_datapath_resp_t cs_etm_decoder__gen_trace_elem_printer(
> resp = cs_etm_decoder__buffer_exception_ret(packet_queue,
> trace_chan_id);
> break;
> + case OCSD_GEN_TRC_ELEM_TIMESTAMP:
> + resp = cs_etm_decoder__do_hard_timestamp(etmq, elem,
> + trace_chan_id);
> + break;
> case OCSD_GEN_TRC_ELEM_PE_CONTEXT:
> - resp = cs_etm_decoder__set_tid(etmq, elem, trace_chan_id);
> + resp = cs_etm_decoder__set_tid(etmq, packet_queue,
> + elem, trace_chan_id);
> break;
> case OCSD_GEN_TRC_ELEM_ADDR_NACC:
> - case OCSD_GEN_TRC_ELEM_TIMESTAMP:
> case OCSD_GEN_TRC_ELEM_CYCLE_COUNT:
> case OCSD_GEN_TRC_ELEM_ADDR_UNKNOWN:
> case OCSD_GEN_TRC_ELEM_EVENT:
> diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
> index 17adf554b679..91496a3a2209 100644
> --- a/tools/perf/util/cs-etm.c
> +++ b/tools/perf/util/cs-etm.c
> @@ -80,6 +80,7 @@ struct cs_etm_queue {
> struct cs_etm_decoder *decoder;
> struct auxtrace_buffer *buffer;
> unsigned int queue_nr;
> + u8 pending_timestamp;
> u64 offset;
> const unsigned char *buf;
> size_t buf_len, buf_used;
> @@ -133,6 +134,19 @@ int cs_etm__get_cpu(u8 trace_chan_id, int *cpu)
> return 0;
> }
>
> +void cs_etm__etmq_set_traceid_queue_timestamp(struct cs_etm_queue *etmq,
> + u8 trace_chan_id)
> +{
> + /*
> + * Wnen a timestamp packet is encountered the backend code
> + * is stopped so that the front end has time to process packets
> + * that were accumulated in the traceID queue. Since there can
> + * be more than one channel per cs_etm_queue, we need to specify
> + * what traceID queue needs servicing.
> + */
> + etmq->pending_timestamp = trace_chan_id;
> +}
> +
> static void cs_etm__clear_packet_queue(struct cs_etm_packet_queue *queue)
> {
> int i;
> @@ -942,6 +956,11 @@ int cs_etm__etmq_set_tid(struct cs_etm_queue *etmq,
> return 0;
> }
>
> +bool cs_etm__etmq_is_timeless(struct cs_etm_queue *etmq)
> +{
> + return !!etmq->etm->timeless_decoding;
> +}
> +
> static int cs_etm__synth_instruction_sample(struct cs_etm_queue *etmq,
> struct cs_etm_traceid_queue *tidq,
> u64 addr, u64 period)
> diff --git a/tools/perf/util/cs-etm.h b/tools/perf/util/cs-etm.h
> index b2a7628620bf..33b57e748c3d 100644
> --- a/tools/perf/util/cs-etm.h
> +++ b/tools/perf/util/cs-etm.h
> @@ -150,6 +150,9 @@ struct cs_etm_packet_queue {
> u32 packet_count;
> u32 head;
> u32 tail;
> + u32 instr_count;
> + u64 timestamp;
> + u64 next_timestamp;
> struct cs_etm_packet packet_buffer[CS_ETM_PACKET_MAX_BUFFER];
> };
>
> @@ -183,6 +186,9 @@ int cs_etm__process_auxtrace_info(union perf_event *event,
> int cs_etm__get_cpu(u8 trace_chan_id, int *cpu);
> int cs_etm__etmq_set_tid(struct cs_etm_queue *etmq,
> pid_t tid, u8 trace_chan_id);
> +bool cs_etm__etmq_is_timeless(struct cs_etm_queue *etmq);
> +void cs_etm__etmq_set_traceid_queue_timestamp(struct cs_etm_queue *etmq,
> + u8 trace_chan_id);
> struct cs_etm_packet_queue
> *cs_etm__etmq_get_packet_queue(struct cs_etm_queue *etmq, u8 trace_chan_id);
> #else
> @@ -207,6 +213,17 @@ static inline int cs_etm__etmq_set_tid(
> return -1;
> }
>
> +static inline bool cs_etm__etmq_is_timeless(
> + struct cs_etm_queue *etmq __maybe_unused)
> +{
> + /* What else to return? */
> + return true;
> +}
> +
> +static inline void cs_etm__etmq_set_traceid_queue_timestamp(
> + struct cs_etm_queue *etmq __maybe_unused,
> + u8 trace_chan_id __maybe_unused) {}
> +
> static inline struct cs_etm_packet_queue *cs_etm__etmq_get_packet_queue(
> struct cs_etm_queue *etmq __maybe_unused,
> u8 trace_chan_id __maybe_unused)
> --
> 2.17.1

--

- Arnaldo

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