Hi Leo

On Mon, 3 Feb 2020 at 01:52, Leo Yan leo.yan@linaro.org wrote:

If use option '--itrace=iNNN' with Arm CoreSight trace data, perf tool fails inject instruction samples; the root cause is the packets are only switched for branch samples and last branches but not for instruction samples, so the new coming packets cannot be properly handled for only synthesizing instruction samples.

To fix this issue, this patch switches packets for instruction samples.

Signed-off-by: Leo Yan leo.yan@linaro.org

tools/perf/util/cs-etm.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c index 5471045ebf5c..3dd5ba34a2c2 100644 --- a/tools/perf/util/cs-etm.c +++ b/tools/perf/util/cs-etm.c @@ -1404,7 +1404,8 @@ static int cs_etm__sample(struct cs_etm_queue *etmq, } }

•   if (etm->sample_branches || etm->synth_opts.last_branch) {
  

•   if (etm->sample_branches || etm->synth_opts.last_branch ||
  

•       etm->sample_instructions) {
            /*
             * Swap PACKET with PREV_PACKET: PACKET becomes PREV_PACKET for
             * the next incoming packet.
  

@@ -1476,7 +1477,8 @@ static int cs_etm__flush(struct cs_etm_queue *etmq, }

swap_packet:

•   if (etm->sample_branches || etm->synth_opts.last_branch) {
  

•   if (etm->sample_branches || etm->synth_opts.last_branch ||
  

•       etm->sample_instructions) {
            /*
             * Swap PACKET with PREV_PACKET: PACKET becomes PREV_PACKET for
             * the next incoming packet.
  

-- 2.17.1

if is worth putting the 'if <options> { swap packet }' into a separate function as it appears twice in identical form? Might help if more options for swap packet are needed later.

Either way

Reviewed by: Mike Leach mike.leach@linaro.org

On Wed, Feb 05, 2020 at 04:09:01PM +0000, Mike Leach wrote:

Hi Leo,

There are a couple of typos in the comments below, but I also believe that the sample loop could be considerably simplified

On Mon, 3 Feb 2020 at 01:52, Leo Yan leo.yan@linaro.org wrote:

...

When 'etm->instructions_sample_period' is less than 'tidq->period_instructions', the function cs_etm__sample() cannot handle this case properly with its logic.

Let's see below flow as an example:

• If we set itrace option '--itrace=i4', then function cs_etm__sample() has variables with initialized values:

  tidq->period_instructions = 0 etm->instructions_sample_period = 4

• When the first packet is coming:

  packet->instr_count = 10; the number of instructions executed in this packet is 10, thus update period_instructions as below:

  tidq->period_instructions = 0 + 10 = 10 instrs_over = 10 - 4 = 6 offset = 10 - 6 - 1 = 3 tidq->period_instructions = instrs_over = 6

• When the second packet is coming:

  packet->instr_count = 10; in the second pass, assume 10 instructions in the trace sample again:

  tidq->period_instructions = 6 + 10 = 16 instrs_over = 16 - 4 = 12 offset = 10 - 12 - 1 = -3 -> the negative value tidq->period_instructions = instrs_over = 12

So after handle these two packets, there have below issues:

The first issue is that cs_etm__instr_addr() returns the address within the current trace sample of the instruction related to offset, so the offset is supposed to be always unsigned value. But in fact, function cs_etm__sample() might calculate a negative offset value (in handling the second packet, the offset is -3) and pass to cs_etm__instr_addr() with u64 type with a big positive integer.

The second issue is it only synthesizes 2 samples for sample period = 4. In theory, every packet has 10 instructions so the two packets have total 20 instructions, 20 instructions should generate 5 samples (4 x 5 = 20). This is because cs_etm__sample() only calls once cs_etm__synth_instruction_sample() to generate instruction sample per range packet.

This patch fixes the logic in function cs_etm__sample(); the basic idea is to divide into three parts for handling coming packet:

• The first part is for synthesizing the first instruction sample, it combines the instructions from the tail of previous packet and the instructions from the head of the new packet;
• The second part is to simply generate samples with sample period aligned;
• The third part is the tail of new packet, the rest instructions will be left for the sequential sample handling.

Suggested-by: Mike Leach mike.leach@linaro.org Signed-off-by: Leo Yan leo.yan@linaro.org

---

tools/perf/util/cs-etm.c | 105 ++++++++++++++++++++++++++++++++++----- 1 file changed, 92 insertions(+), 13 deletions(-)

diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c index 3e28462609e7..c5a05f728eac 100644 --- a/tools/perf/util/cs-etm.c +++ b/tools/perf/util/cs-etm.c @@ -1360,23 +1360,102 @@ static int cs_etm__sample(struct cs_etm_queue *etmq, * TODO: allow period to be defined in cycles and clock time */

•           /* Get number of instructions executed after the sample point */
  

•           u64 instrs_over = tidq->period_instructions -
  

•                   etm->instructions_sample_period;
  

•           /*
  

•            * Below diagram demonstrates the instruction samples
  

•            * generation flows:
  

•            *
  

•            *    Instrs     Instrs       Instrs       Instrs
  

•            *   Sample(n)  Sample(n+1)  Sample(n+2)  Sample(n+3)
  

•            *    |            |            |            |
  

•            *    V            V            V            V
  

•            *   --------------------------------------------------
  

•            *            ^                                  ^
  

•            *            |                                  |
  

•            *         Period                             Period
  

•            *    instructions(Pi)                   instructions(Pi')
  

•            *
  

•            *            |                                  |
  

•            *            \---------------- -----------------/
  

•            *                             V
  

•            *                      instrs_executed
  

•            *
  

•            * Period instructions (Pi) contains the the number of
  

•            * instructions executed after the sample point(n).  When a new
  

•            * instruction packet is coming and generate for the next sample
  

•            * (n+1), it combines with two parts instructions, one is the
  

•            * tail of the old packet and another is the head of the new
  

•            * coming packet.  So 'head' variable is used to cauclate the
  

typo : s/cauclate/calculate

Used checkpatch.pl but didn't see any complaints for this.

Thanks for pointing out and will fix it.

...

•            * instruction numbers in the new packet for sample(n+1).
  

•            *
  

•            * Sample(n+2) and sample(n+3) consume the instructions with
  

•            * sample period, so directly generate samples based on the
  

•            * sampe period.
  

•            *
  

typo: s/sampe/sample

Will fix.

...

•            * After sample(n+3), the rest instructions will be used by
  

•            * later packet; so use 'instrs_over' to track the rest
  

•            * instruction number and it is assigned to
  

•            * 'tidq->period_instructions' for next round calculation.
  

•            */
  

•           u64 head, offset = 0;
  

•           u64 addr;
  
            /*
  

•            * Calculate the address of the sampled instruction (-1 as
  

•            * sample is reported as though instruction has just been
  

•            * executed, but PC has not advanced to next instruction)
  

•            * 'instrs_over' is the number of instructions executed after
  

•            * sample points, initialise it to 'instrs_executed' and will
  

•            * decrease it for consumed instructions in every synthesized
  

•            * instruction sample.
             */
  

•           u64 offset = (instrs_executed - instrs_over - 1);
  

•           u64 addr = cs_etm__instr_addr(etmq, trace_chan_id,
  

•                                         tidq->packet, offset);
  

•           u64 instrs_over = instrs_executed;
  
  

•           ret = cs_etm__synth_instruction_sample(
  

•                   etmq, tidq, addr, etm->instructions_sample_period);
  

•           if (ret)
  

•                   return ret;
  

•           /*
  

•            * 'head' is the instructions number of the head in the new
  

•            * packet, it combines with the tail of previous packet to
  

•            * generate a sample.  So 'head' uses the sample period to
  

•            * decrease the instruction number introduced by the previous
  

•            * packet.
  

•            */
  

•           head = etm->instructions_sample_period -
  

•                             (tidq->period_instructions - instrs_executed);
  

•           if (head) {
  

•                   offset = head;
  

•                   /*
  

•                    * Calculate the address of the sampled instruction (-1
  

•                    * as sample is reported as though instruction has just
  

•                    * been executed, but PC has not advanced to next
  

•                    * instruction)
  

•                    */
  

•                   addr = cs_etm__instr_addr(etmq, trace_chan_id,
  

•                                             tidq->packet, offset - 1);
  

•                   ret = cs_etm__synth_instruction_sample(
  

•                           etmq, tidq, addr,
  

•                           etm->instructions_sample_period);
  

•                   if (ret)
  

•                           return ret;
  

•                   instrs_over -= head;
  

•           }
  

•           while (instrs_over >= etm->instructions_sample_period) {
  

•                   offset += etm->instructions_sample_period;
  

•                   /*
  

•                    * Calculate the address of the sampled instruction (-1
  

•                    * as sample is reported as though instruction has just
  

•                    * been executed, but PC has not advanced to next
  

•                    * instruction)
  

•                    */
  

•                   addr = cs_etm__instr_addr(etmq, trace_chan_id,
  

•                                             tidq->packet, offset - 1);
  

•                   ret = cs_etm__synth_instruction_sample(
  

•                           etmq, tidq, addr,
  

•                           etm->instructions_sample_period);
  

•                   if (ret)
  

•                           return ret;
  

•                   instrs_over -= etm->instructions_sample_period;
  

•           }
  
            /* Carry remaining instructions into next sample period */
            tidq->period_instructions = instrs_over;
  

-- 2.17.1

I believe the following change would work and make for easier reading...

.... at the start of the function remove instrs_executed and replace .... /* get instructions remainder from previous packet */ u64 instrs_prev = tidq->period_instructions;

/* set available instructions to previous packet remainder + the current packet count */ tidq->period_instructions += tidq->packet->instr_count;

.... within the if(etm->sample_instructions && ...) statement I would be more explicit what the elements of the diagram are ....

/*

• Below diagram demonstrates the instruction samples
• generation flows:
• Instrs Instrs Instrs Instrs
• Sample(n) Sample(n+1) Sample(n+2) Sample(n+3)
• | | | |
• V V V V

• ---

•        ^                                  ^
  

•        |                                  |
  

•     Period                             Period
  

• instructions(Pi) instructions(Pi')

•        |                                  |
  

•        \---------------- -----------------/
  

•                         V
  

•                  tidq->packet->instr_count;
  

• Instrs Sample(n...) are the synthesised samples occuring every

etm->instructions_sample_period

• instructions - as defined on the perf command line. Sample(n) being

the last sample before the

• current etm packet, n+1 to n+3 samples generated from the current etm packet.
• tidq->packet->instr_count represents the number of instructions in

the current etm packet.

• Period instructions (Pi) contains the the number of instructions

executed after the sample point(n)

• from the previous etm packet. This will always be less than

etm->instructions_sample_period.

.... continue with explanation here ....

.... then we can simplify the loop code removing some of the temporary variables ....

/* get the initial offset into the current packet instructions (entry conditions ensure that instrs_prev < etm->instructions_sample_period) */ u64 offset = etm->instructions_sample_period - instrs_prev; u64 addr;

/* Prepare last branches for instruction sample */ if (etm->synth_opts.last_branch) cs_etm__copy_last_branch_rb(etmq, tidq);

while (tidq->period_instructions >= etm->instructions_sample_period) {

  /*
   * Calculate the address of the sampled instruction (-1
   * as sample is reported as though instruction has just
   * been executed, but PC has not advanced to next
   * instruction)
   */
addr = cs_etm__instr_addr(etmq, trace_chan_id, tidq->packet, offset - 1);
ret = cs_etm__synth_instruction_sample( etmq, tidq, addr,
            etm->instructions_sample_period);
if (ret)
    return ret;

offset += etm->instructions_sample_period;
tidq->period_instructions -= etm->instructions_sample_period;

}

..... I believe the above should work, but cannot claim to have tried it out. What do you think?

Agree. To be honest, I considered to use your suggested way, but I worried about the boundary conditions for 'offset', so went back to use explict method with two code segments (head and sequential samples).

After review the suggested code, I don't find any issue. Will refine code as this way and give testing for it.

Very appreciate the suggestions :)

Leo

Reviewed by: Mike Leach mike.leach@linaro.org

On Mon, 3 Feb 2020 at 01:53, Leo Yan leo.yan@linaro.org wrote:

If an instruction range packet can generate multiple instruction samples, these samples share the same last branches; it's not necessary to copy the same last branches repeatedly for these samples within the same packet.

This patch moves out the last branches copying from function cs_etm__synth_instruction_sample(), and execute it prior to generating instruction samples.

Signed-off-by: Leo Yan leo.yan@linaro.org

tools/perf/util/cs-etm.c | 22 +++++++++++++++++----- 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c index c5a05f728eac..dbddf1eec2be 100644 --- a/tools/perf/util/cs-etm.c +++ b/tools/perf/util/cs-etm.c @@ -1134,10 +1134,8 @@ static int cs_etm__synth_instruction_sample(struct cs_etm_queue *etmq,

    cs_etm__copy_insn(etmq, tidq->trace_chan_id, tidq->packet, &sample);

•   if (etm->synth_opts.last_branch) {
  

•           cs_etm__copy_last_branch_rb(etmq, tidq);
  

•   if (etm->synth_opts.last_branch)
            sample.branch_stack = tidq->last_branch;
  

•   }
  
    if (etm->synth_opts.inject) {
            ret = cs_etm__inject_event(event, &sample,
  

@@ -1407,6 +1405,10 @@ static int cs_etm__sample(struct cs_etm_queue *etmq, */ u64 instrs_over = instrs_executed;

•           /* Prepare last branches for instruction sample */
  

•           if (etm->synth_opts.last_branch)
  

•                   cs_etm__copy_last_branch_rb(etmq, tidq);
  

•           /*
             * 'head' is the instructions number of the head in the new
             * packet, it combines with the tail of previous packet to
  

@@ -1526,6 +1528,11 @@ static int cs_etm__flush(struct cs_etm_queue *etmq,

    if (etmq->etm->synth_opts.last_branch &&
        tidq->prev_packet->sample_type == CS_ETM_RANGE) {

•           u64 addr;
  

•           /* Prepare last branches for instruction sample */
  

•           cs_etm__copy_last_branch_rb(etmq, tidq);
  

•           /*
             * Generate a last branch event for the branches left in the
             * circular buffer at the end of the trace.
  

@@ -1533,7 +1540,7 @@ static int cs_etm__flush(struct cs_etm_queue *etmq, * Use the address of the end of the last reported execution * range */

•           u64 addr = cs_etm__last_executed_instr(tidq->prev_packet);
  

•           addr = cs_etm__last_executed_instr(tidq->prev_packet);
  
            err = cs_etm__synth_instruction_sample(
                    etmq, tidq, addr,
  

@@ -1587,11 +1594,16 @@ static int cs_etm__end_block(struct cs_etm_queue *etmq, */ if (etmq->etm->synth_opts.last_branch && tidq->prev_packet->sample_type == CS_ETM_RANGE) {

•           u64 addr;
  

•           /* Prepare last branches for instruction sample */
  

•           cs_etm__copy_last_branch_rb(etmq, tidq);
  

•           /*
             * Use the address of the end of the last reported execution
             * range.
             */
  

•           u64 addr = cs_etm__last_executed_instr(tidq->prev_packet);
  

•           addr = cs_etm__last_executed_instr(tidq->prev_packet);
  
            err = cs_etm__synth_instruction_sample(
                    etmq, tidq, addr,
  

-- 2.17.1

Reviewed by: Mike Leach mike.leach@linaro.org

On Mon, 3 Feb 2020 at 01:53, Leo Yan leo.yan@linaro.org wrote:

The variable 'offset' in function cs_etm__sample() is u64 type, it's not appropriate to check it with 'while (offset > 0)'; this patch changes to 'while (offset)'.

Signed-off-by: Leo Yan leo.yan@linaro.org

tools/perf/util/cs-etm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c index dbddf1eec2be..720108bd8dba 100644 --- a/tools/perf/util/cs-etm.c +++ b/tools/perf/util/cs-etm.c @@ -945,7 +945,7 @@ static inline u64 cs_etm__instr_addr(struct cs_etm_queue *etmq, if (packet->isa == CS_ETM_ISA_T32) { u64 addr = packet->start_addr;

•           while (offset > 0) {
  

•           while (offset) {
                    addr += cs_etm__t32_instr_size(etmq,
                                                   trace_chan_id, addr);
                    offset--;
  

-- 2.17.1