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SubjectRe: [RFT v2 1/4] perf cs-etm: Generate sample for missed packets
On Tue, May 22, 2018 at 04:39:20PM +0800, Leo Yan wrote:

[...]

Rather than the patch I posted in my previous email, I think below new
patch is more reasonable for me.

In the below change, 'etmq->prev_packet' is only used to store the
previous CS_ETM_RANGE packet, we don't need to save CS_ETM_TRACE_ON
packet into 'etmq->prev_packet'.

On the other hand, cs_etm__flush() can use 'etmq->period_instructions'
to indicate if need to generate instruction sample or not. If it's
non-zero, then generate instruction sample and
'etmq->period_instructions' will be cleared; so next time if there
have more tracing CS_ETM_TRACE_ON packet, it can skip to generate
instruction sample due 'etmq->period_instructions' is zero.

How about you think for this?

Thanks,
Leo Yan


diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
index 822ba91..dd354ad 100644
--- a/tools/perf/util/cs-etm.c
+++ b/tools/perf/util/cs-etm.c
@@ -495,6 +495,13 @@ static inline void cs_etm__reset_last_branch_rb(struct cs_etm_queue *etmq)
static inline u64 cs_etm__last_executed_instr(struct cs_etm_packet *packet)
{
/*
+ * The packet is the start tracing packet if the end_addr is zero,
+ * returns 0 for this case.
+ */
+ if (!packet->end_addr)
+ return 0;
+
+ /*
* The packet records the execution range with an exclusive end address
*
* A64 instructions are constant size, so the last executed
@@ -897,13 +904,27 @@ static int cs_etm__sample(struct cs_etm_queue *etmq)
etmq->period_instructions = instrs_over;
}

- if (etm->sample_branches &&
- etmq->prev_packet &&
- etmq->prev_packet->sample_type == CS_ETM_RANGE &&
- etmq->prev_packet->last_instr_taken_branch) {
- ret = cs_etm__synth_branch_sample(etmq);
- if (ret)
- return ret;
+ if (etm->sample_branches && etmq->prev_packet) {
+ bool generate_sample = false;
+
+ /* Generate sample for start tracing packet */
+ if (etmq->prev_packet->sample_type == 0)
+ generate_sample = true;
+
+ /* Generate sample for exception packet */
+ if (etmq->prev_packet->exc == true)
+ generate_sample = true;
+
+ /* Generate sample for normal branch packet */
+ if (etmq->prev_packet->sample_type == CS_ETM_RANGE &&
+ etmq->prev_packet->last_instr_taken_branch)
+ generate_sample = true;
+
+ if (generate_sample) {
+ ret = cs_etm__synth_branch_sample(etmq);
+ if (ret)
+ return ret;
+ }
}

if (etm->sample_branches || etm->synth_opts.last_branch) {
@@ -922,11 +943,12 @@ static int cs_etm__sample(struct cs_etm_queue *etmq)
static int cs_etm__flush(struct cs_etm_queue *etmq)
{
int err = 0;
- struct cs_etm_packet *tmp;

if (etmq->etm->synth_opts.last_branch &&
etmq->prev_packet &&
- etmq->prev_packet->sample_type == CS_ETM_RANGE) {
+ etmq->prev_packet->sample_type == CS_ETM_RANGE &&
+ etmq->period_instructions) {
+
/*
* Generate a last branch event for the branches left in the
* circular buffer at the end of the trace.
@@ -940,14 +962,6 @@ static int cs_etm__flush(struct cs_etm_queue *etmq)
etmq, addr,
etmq->period_instructions);
etmq->period_instructions = 0;
-
- /*
- * Swap PACKET with PREV_PACKET: PACKET becomes PREV_PACKET for
- * the next incoming packet.
- */
- tmp = etmq->packet;
- etmq->packet = etmq->prev_packet;
- etmq->prev_packet = tmp;
}

return err;
--
2.7.4
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