Measure/Guess Execution Time of C/C++ Methods

[rweickelt]

Hi,

I want to determine the execution time of some methods in a program written in C++. The program runs in the simulator.

My first attempt was xta. While this works for some methods, xta gives up in some cases.

xta script:

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load <binary>
analyze function <mangled-method-name>
set required - 10 ms
print summary
exit

command line

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>xta -source script.xta
>Route(1) function: <mangled-method-name>
    Fail (timing violation), Num Paths: 4, Violation: Unresolved, Required: 100,0 ms, Worst: Unresolved, Min Core Frequency: Unresolved

So I gave up on that. My second attempt was then, to perform a run-time analysis. I've executed xsim and run the output through gprof:

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>xsim --gprof --max-cycles 100000 <binary>
>xobjdump --split <binary>
>gprof image_n0c0_2.elf tile\[0\]_core0.gprof  --demangle > profile
># repeat for each core

The output looks like

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Each sample counts as 2e-06 milliseconds.
  %   cumulative   self              self     total           
 time milliseco  millisec    calls  um/call  um/call  name    
 47.08      0.00     0.00        1   288.13   288.13  <mangled-method-name>

What does um mean here? In comparison xta produces for the same method:

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Route(1) function: _ZN11Transformer15run_processDataEv
    Fail (missing loop iterations) with 36 unknowns, Num Paths: 128, Slack: 10,0 ms, Required: 10,0 ms, Worst: 4,2 us, Min Core Frequency: 0 MHz

Since this method calls a xc-method which then transfers data via an xlink channel, it would make sense, if the profiled time is much higher than the estimated time. But I'm confused, if um in the gprof output means microseconds. Does anybody know?

[segher]

"milliseconds" and "m" are taken from the gmon file (the
gprof input file); they are the name of the unit the histogram
is counted in, and its abbreviation. "um" means a millionth
of that unit, a micro-millisecond, that is a nanosecond.

No idea why xsim uses such a strange unit, but there you
have it :-)

[rweickelt]

Thank You. Indeed very strange.