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Subject[PATCH 52/85] perf cs-etm: Add notion of time to decoding code
Date
From: Mathieu Poirier <mathieu.poirier@linaro.org>

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>
Tested-by: Leo Yan <leo.yan@linaro.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Suzuki Poulouse <suzuki.poulose@arm.com>
Cc: coresight@lists.linaro.org
Cc: linux-arm-kernel@lists.infradead.org
Link: http://lkml.kernel.org/r/20190524173508.29044-17-mathieu.poirier@linaro.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
.../perf/util/cs-etm-decoder/cs-etm-decoder.c | 111 +++++++++++++++++-
tools/perf/util/cs-etm.c | 19 +++
tools/perf/util/cs-etm.h | 17 +++
3 files changed, 143 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..bb45e23018ee 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 +269,75 @@ 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;
+ 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 +379,8 @@ 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 +435,23 @@ 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 +459,11 @@ 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 +496,7 @@ 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 +510,12 @@ 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 +545,7 @@ 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 +556,15 @@ 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)
--
2.20.1
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