This patch series is to address the issue for synthesizing instruction samples, especially when the instruction sample period is small enough, the current logic cannot synthesize multiple instruction samples within one instruction range packet.
To fix this issue, patch 0001 avoids to reset the last branches for every instruction sample; if reset the last branches when every time generate instruction sample, then the later samples in the same range packet cannot use the last branches anymore.
Patch 0002 is the main patch to fix the logic for synthesizing instruction samples; it allows to handle different instruction periods.
Patch 0003 is an optimization for copying last branches; it only copies last branches once if the instruction samples share the same last branches.
Patch 0004 is a minor fix for unsigned variable comparison to zero.
To verify my changing for synthesizing instruction samples, I added some logs in the code, and reviewed the output log manually for instuctions samples. The below commands are tested on DB410c board:
# perf script --itrace=i2 # perf script --itrace=i2li16 # perf inject --itrace=i2il16 -i perf.data -o perf.data.new # perf inject --itrace=i100il16 -i perf.data -o perf.data.new
Leo Yan (4): perf cs-etm: Continuously record last branches perf cs-etm: Correct synthesizing instruction samples perf cs-etm: Optimize copying last branches perf cs-etm: Fix unsigned variable comparison to zero
tools/perf/util/cs-etm.c | 137 ++++++++++++++++++++++++++++++++------- 1 file changed, 115 insertions(+), 22 deletions(-)
Every time synthesize instruction sample, the last branches recording will be reset. This would be fine if the instruction period is big enough, for example if we use the option '--itrace=i100000', the last branch array is reset for every instruction sample (10000 instructions per period); before generate the next instruction sample, there has the enough packets coming to fill last branch array. On the other hand, if set a very small period, the packets will be significantly reduced between two continuous instruction samples, thus if the last branch array is reset for the previous instruction sample, it's almost empty for the next instruction sample.
To allow the last branches to work for any instruction periods, this patch avoids to reset the last branches for every instruction sample and only reset it when flush the trace data. The last branches will be reset only for two cases, one is for trace starting, another case is for discontinuous trace; thus it can continuously record last branches.
Signed-off-by: Leo Yan leo.yan@linaro.org --- tools/perf/util/cs-etm.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c index f5f855fff412..8be6d010ae84 100644 --- a/tools/perf/util/cs-etm.c +++ b/tools/perf/util/cs-etm.c @@ -1153,9 +1153,6 @@ static int cs_etm__synth_instruction_sample(struct cs_etm_queue *etmq, "CS ETM Trace: failed to deliver instruction event, error %d\n", ret);
- if (etm->synth_opts.last_branch) - cs_etm__reset_last_branch_rb(tidq); - return ret; }
@@ -1486,6 +1483,10 @@ static int cs_etm__flush(struct cs_etm_queue *etmq, tidq->prev_packet = tmp; }
+ /* Reset last branches after flush the trace */ + if (etm->synth_opts.last_branch) + cs_etm__reset_last_branch_rb(tidq); + return err; }
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 to next time handling with sequential packet.
Suggested-by: Mike Leach mike.leach@linaro.org Signed-off-by: Leo Yan leo.yan@linaro.org --- tools/perf/util/cs-etm.c | 106 ++++++++++++++++++++++++++++++++++----- 1 file changed, 93 insertions(+), 13 deletions(-)
diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c index 8be6d010ae84..8e9eb7583bcd 100644 --- a/tools/perf/util/cs-etm.c +++ b/tools/perf/util/cs-etm.c @@ -1360,23 +1360,103 @@ 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 is used to demonstrate 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 + * + * When the new instruction packet is coming, period + * instructions (Pi) contains the the number of instructions + * executed after the sample point(n). So for the next sample + * point(n+1), it is combined the two parts instructions, one + * is the tail of the old packet and another is the head of + * the new coming packet. So we use 'head' variable to cauclate + * the instruction numbers in the new packet for sample(n+1). + * + * For sample(n+2) and sample(n+3), they consume the instruction + * for sample period, so we directly generate samples based on + * the sampe period. + * + * After sample(n+3), there still leave some instructions which + * will be used by later packet; so we use 'instrs_over' to + * track the rest instruction number and its final value + * presents the tail of the packet, it will be 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;
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 once 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 8e9eb7583bcd..d9a857abaca8 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, @@ -1408,6 +1406,10 @@ 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, @@ -1586,11 +1593,16 @@ 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,
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 d9a857abaca8..52fe7d6d4f29 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--;
On Thu, 24 Oct 2019 at 09:15, Leo Yan leo.yan@linaro.org wrote:
This patch series is to address the issue for synthesizing instruction samples, especially when the instruction sample period is small enough, the current logic cannot synthesize multiple instruction samples within one instruction range packet.
To fix this issue, patch 0001 avoids to reset the last branches for every instruction sample; if reset the last branches when every time generate instruction sample, then the later samples in the same range packet cannot use the last branches anymore.
Patch 0002 is the main patch to fix the logic for synthesizing instruction samples; it allows to handle different instruction periods.
Patch 0003 is an optimization for copying last branches; it only copies last branches once if the instruction samples share the same last branches.
Patch 0004 is a minor fix for unsigned variable comparison to zero.
To verify my changing for synthesizing instruction samples, I added some logs in the code, and reviewed the output log manually for instuctions samples. The below commands are tested on DB410c board:
# perf script --itrace=i2 # perf script --itrace=i2li16 # perf inject --itrace=i2il16 -i perf.data -o perf.data.new # perf inject --itrace=i100il16 -i perf.data -o perf.data.new
Leo Yan (4): perf cs-etm: Continuously record last branches perf cs-etm: Correct synthesizing instruction samples perf cs-etm: Optimize copying last branches perf cs-etm: Fix unsigned variable comparison to zero
I have reviewed and agree with the changes in this set but won't move forward until Mike has looked at patch 2/4.
Thanks, Mathieu
tools/perf/util/cs-etm.c | 137 ++++++++++++++++++++++++++++++++------- 1 file changed, 115 insertions(+), 22 deletions(-)
-- 2.17.1
On Thu, Oct 31, 2019 at 11:14:15AM -0600, Mathieu Poirier wrote:
On Thu, 24 Oct 2019 at 09:15, Leo Yan leo.yan@linaro.org wrote:
This patch series is to address the issue for synthesizing instruction samples, especially when the instruction sample period is small enough, the current logic cannot synthesize multiple instruction samples within one instruction range packet.
To fix this issue, patch 0001 avoids to reset the last branches for every instruction sample; if reset the last branches when every time generate instruction sample, then the later samples in the same range packet cannot use the last branches anymore.
Patch 0002 is the main patch to fix the logic for synthesizing instruction samples; it allows to handle different instruction periods.
Patch 0003 is an optimization for copying last branches; it only copies last branches once if the instruction samples share the same last branches.
Patch 0004 is a minor fix for unsigned variable comparison to zero.
To verify my changing for synthesizing instruction samples, I added some logs in the code, and reviewed the output log manually for instuctions samples. The below commands are tested on DB410c board:
# perf script --itrace=i2 # perf script --itrace=i2li16 # perf inject --itrace=i2il16 -i perf.data -o perf.data.new # perf inject --itrace=i100il16 -i perf.data -o perf.data.new
Leo Yan (4): perf cs-etm: Continuously record last branches perf cs-etm: Correct synthesizing instruction samples perf cs-etm: Optimize copying last branches perf cs-etm: Fix unsigned variable comparison to zero
I have reviewed and agree with the changes in this set but won't move forward until Mike has looked at patch 2/4.
Thanks a lot for reviewing, Mathieu.
Sorry I forgot to loop Mike in this patch set, and respin patch for v2 and have sent to mailing list. @Mike, please review patch set v2 as you received, Thanks!
Thanks, Leo Yan
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Leo Yan -
Mathieu Poirier