[v2,0/4] perf cs-etm: Fix synthesizing instruction samples
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Message ID 20191101020750.29063-1-leo.yan@linaro.org
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  • perf cs-etm: Fix synthesizing instruction samples
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Leo Yan Nov. 1, 2019, 2:07 a.m. UTC
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

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=i2il16
  # perf inject --itrace=i2il16 -i perf.data -o perf.data.new
  # perf inject --itrace=i100il16 -i perf.data -o perf.data.new

Changes from v1:
* Rebased patch set on perf/core branch with latest commit 9fec3cd5fa4a
  ("perf map: Check if the map still has some refcounts on exit").

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(-)