On Mon, Nov 19, 2018 at 11:27:59AM -0700, Mathieu Poirier wrote:
On Sun, Nov 11, 2018 at 12:59:41PM +0800, Leo Yan wrote:
As described in OpenCSD (CoreSight decoder lib), in the decoding stream it includes one trace element with type OCSD_GEN_TRC_ELEM_NO_SYNC; the element indicates 'either at start of decode, or after overflow / bad packet', we should take it as a signal for the tracing off and this will cause tracing discontinuity. From the trace dump with 'perf script', sometimes the element OCSD_GEN_TRC_ELEM_NO_SYNC collaborates with element OCSD_GEN_TRC_ELEM_TRACE_ON to show the tracing flow have been turned off and on, in this case the cs-etm code has handled TRACE_ON packet well so we observe the tracing discontinuity; but in another case it only inserts the element OCSD_GEN_TRC_ELEM_NO_SYNC into instructions packets, we miss to handle the case if has only standalone NO_SYNC element and users cannot receive the info for tracing discontinuity.
This patch introduces new type CS_ETM_TRACE_OFF to generate packet for receiving element OCSD_GEN_TRC_ELEM_NO_SYNC from decoder; when generate sample, CS_ETM_TRACE_OFF packet has almost the same behaviour with
Here you have used the word "almost", leading me to beleive there are cases where the handling of TRACE_ON and NO_SYNC packets differ, but the implementation enacts the same behavior for both.
Mike or Robert, can you confirm that TRACE_ON and NO_SYNC packets should be treated the same way?
I also would like to get suggestions/comments from Mike and Rob.
For NO_SYNC packet, Mike before has given some explination for it:
"looking at the decoder flow, when the decoder is reset, then it is returned to an unsynchronised state and a NO_SYNC will be output. With perf, it can concatenate multiple trace buffers into a single section of the perf.data file. To ensure that the decode process can see the start of a new buffer, the drivers will insert a barrier packet between different buffers so that the decoder can spot the boundaries. When the decoder hits a barrier packet it will automatically reset so that it correctly decodes the next trace buffer. This could be what you are seeing here."
So I think there still have some difference between TRACE_ON and NO_SYNC packets, TRACE_ON packet indicates the start of trace and it's also possible caused by tracing discontinuity; NO_SYNC packets usually caused by an unsynchronised state. But both of them presents discontinuity in perf trace data.
I prefer to use two different packet types to present them, this can let the code to be more readable and easier to be maintained later.
If you agree with this, I also will rephrase the commit log to avoid confusion that these two packets are the same thing.
Leo, if handling of the TRACE_ON and NO_SYNC packets is the same then we should treat them the same way in cs_etm_decoder__gen_trace_elem_printer(), i.e simply call cs_etm_decoder__buffer_trace_on(). That way packet handling in cs-etm.c doesn't change. Otherwise see my comments below.
CS_ETM_TRACE_ON packet: both of them invokes cs_etm__flush() to generate samples for the previous instructions packet, and in cs_etm__sample() it also needs to generate samples if TRACE_OFF packet is followed by one sequential instructions packet. This patch also converts the address to 0 for TRACE_OFF packet, this is same with TRACE_ON packet as well.
Signed-off-by: Leo Yan leo.yan@linaro.org
tools/perf/util/cs-etm-decoder/cs-etm-decoder.c | 10 ++++++++++ tools/perf/util/cs-etm-decoder/cs-etm-decoder.h | 7 ++++--- tools/perf/util/cs-etm.c | 15 +++++++++++---- 3 files changed, 25 insertions(+), 7 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 5efb616..9d52727 100644 --- a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c +++ b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c @@ -369,6 +369,14 @@ cs_etm_decoder__buffer_range(struct cs_etm_decoder *decoder, } static ocsd_datapath_resp_t +cs_etm_decoder__buffer_trace_off(struct cs_etm_decoder *decoder,
const uint8_t trace_chan_id)+{
- return cs_etm_decoder__buffer_packet(decoder, trace_chan_id,
CS_ETM_TRACE_OFF);+}
+static ocsd_datapath_resp_t cs_etm_decoder__buffer_trace_on(struct cs_etm_decoder *decoder, const uint8_t trace_chan_id) { @@ -389,6 +397,8 @@ static ocsd_datapath_resp_t cs_etm_decoder__gen_trace_elem_printer( case OCSD_GEN_TRC_ELEM_UNKNOWN: break; case OCSD_GEN_TRC_ELEM_NO_SYNC:
resp = cs_etm_decoder__buffer_trace_off(decoder,trace_chan_id);If we want to handle NO_SYNC element types, why introduce a "trace_off" function? Wouldn't it make more sense to call it cs_etm_decoder__buffer_no_sync() ?
Will change to cs_etm_decoder__buffer_no_sync().
decoder->trace_on = false; break;case OCSD_GEN_TRC_ELEM_TRACE_ON: 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 9351bd1..a38c97c 100644 --- a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.h +++ b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.h @@ -23,9 +23,10 @@ struct cs_etm_buffer { }; enum cs_etm_sample_type {
- CS_ETM_EMPTY = 0,
- CS_ETM_RANGE = 1 << 0,
- CS_ETM_TRACE_ON = 1 << 1,
- CS_ETM_EMPTY = 0,
- CS_ETM_RANGE = 1 << 0,
- CS_ETM_TRACE_ON = 1 << 1,
- CS_ETM_TRACE_OFF = 1 << 2,
CS_ETM_NO_SYNC, see above comment. And please don't use indentation.
Will do this.
}; enum cs_etm_isa { diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c index f4fa877..2a0cef9 100644 --- a/tools/perf/util/cs-etm.c +++ b/tools/perf/util/cs-etm.c @@ -517,8 +517,9 @@ static inline int cs_etm__t32_instr_size(struct cs_etm_queue *etmq, static inline u64 cs_etm__first_executed_instr(struct cs_etm_packet *packet) {
- /* Returns 0 for the CS_ETM_TRACE_ON packet */
- if (packet->sample_type == CS_ETM_TRACE_ON)
- /* Returns 0 for TRACE_ON and TRACE_OFF packets */
- if (packet->sample_type == CS_ETM_TRACE_ON ||
packet->sample_type == CS_ETM_TRACE_OFF)return packet->start_addr; @@ -527,8 +528,9 @@ static inline u64 cs_etm__first_executed_instr(struct cs_etm_packet *packet) static inline u64 cs_etm__last_executed_instr(const struct cs_etm_packet *packet) {
- /* Returns 0 for the CS_ETM_TRACE_ON packet */
- if (packet->sample_type == CS_ETM_TRACE_ON)
- /* Returns 0 for TRACE_ON and TRACE_OFF packets */
- if (packet->sample_type == CS_ETM_TRACE_ON ||
packet->sample_type == CS_ETM_TRACE_OFF)return packet->end_addr - packet->last_instr_size; @@ -930,6 +932,10 @@ static int cs_etm__sample(struct cs_etm_queue *etmq) if (etmq->prev_packet->sample_type == CS_ETM_TRACE_ON) generate_sample = true;
/* Generate sample for tracing off packet */if (etmq->prev_packet->sample_type == CS_ETM_TRACE_OFF)generate_sample = true;- /* Generate sample for branch taken packet */ if (etmq->prev_packet->sample_type == CS_ETM_RANGE && etmq->prev_packet->last_instr_taken_branch)
@@ -1085,6 +1091,7 @@ static int cs_etm__run_decoder(struct cs_etm_queue *etmq) cs_etm__sample(etmq); break; case CS_ETM_TRACE_ON:
case CS_ETM_TRACE_OFF: /* * Discontinuity in trace, flush * previous branch stack-- 2.7.4