Profiling Gnat re. pthread_malloc, pthread_getspecific, system finalisation & tasking.

[Charles Darcy <charlie@mullum.com.au>]

Hello,

    I've profiled an Ada program, which I converted from c++, so that I
might learn why the Ada program performs worse than the c++ version
(approx. 10 times slower). I'm using Gnat 3.13p and gprof on a Linux
(Mandrake 8.0) machine. I've used inlining, O3 optimisation, and
disabled all run-time checks.

    The profile results (below) seem to indicate that pthread_malloc,
pthread_getspecific consume a large portion of processing time, but
these functions are a mystery to me. Is there any way to reduce the
performance cost of these functions ?

    The other expensive sub-programs seem related to tasking and
controlled types, neither of which I directly use. I do use the Booch
components (maps, collections), which may make use of controlled types,
but I am not creating and destroying these as part of my main
processing, so I do not see why the system__finalization_* subprograms
are such a factor. Similarly, as I do not use tasks, I don't understand
why the system__tasking_* subprograms consume a significant portion of
processor time.


(Note: I've renamed my subprograms to *my_subprogram*)

Flat profile:

Each sample counts as 0.01 seconds.
  %   cumulative   self              self     total
 time   seconds   seconds    calls  ms/call  ms/call  name
  8.29     79.07    79.07  4840668     0.02     0.04
*my_main_processing_subprogram*
  7.61    151.64    72.57                             pthread_malloc
  6.43    212.98    61.34
pthread_getspecific
  5.32    263.76    50.78
system__finalization_implementation__initialize__2
  5.09    312.35    48.59                             _free_internal
  4.20    352.44    40.09
system__finalization_implementation__finalize_list
  3.62    386.97    34.53
system__tasking__initialization__set_jmpbuf_address
  2.60    411.73    24.76
system__tasking__initialization__task_unlock__2
  2.42    434.80    23.07  1786603     0.01     0.01  *my_subprogram*
  2.39    457.63    22.83                             pthread_mutex_lock

  2.37    480.24    22.61  1595032     0.01     0.04  *my_subprogram*
  2.17    500.90    20.66
system__tasking__initialization__task_lock__2
  2.13    521.24    20.34
system__soft_links__set_jmpbuf_address_soft
  1.94    539.72    18.48
pthread_mutex_unlock
  1.87    557.56    17.84 557870939     0.00     0.00  *my_subprogram*
  1.72    573.92    16.36 61165604     0.00     0.00  *my_subprogram*
  1.68    589.94    16.02 71029260     0.00     0.00  *my_subprogram*
  1.66    605.78    15.84
system__tasking__initialization__get_sec_stack_addr
  1.60    621.03    15.25
system__finalization_implementation__adjust__2
  1.59    636.16    15.13 12025996     0.00     0.00  *my_subprogram*
  1.42    649.66    13.50
system__tasking__initialization__get_jmpbuf_address
  1.34    662.40    12.74 84209013     0.00     0.00  *my_subprogram*
  1.23    674.13    11.73 84209013     0.00     0.00  *my_subprogram*
  1.20    685.60    11.47
ada__strings__unbounded__adjust__2
  1.10    696.06    10.46 84215790     0.00     0.00  *my_subprogram*
  1.08    706.38    10.32
system__secondary_stack__ss_allocate
  1.07    716.57    10.19                             __gnat_free
  1.07    726.76    10.19                             __gnat_malloc
  1.05    736.77    10.01 84217148     0.00     0.00 *my_subprogram*
  1.02    746.53     9.76 182182420     0.00     0.00  *my_subprogram*
  0.90    755.09     8.56
system__soft_links__get_jmpbuf_address_soft
  0.86    763.31     8.22 288134396     0.00     0.00  *my_subprogram*
  0.85    771.37     8.06
system__finalization_implementation__finalize
  0.80    779.02     7.65                             pthread_free
  0.78    786.45     7.43
ada__strings__search__index__3
  0.74    793.53     7.08
system__tasking__initialization__get_current_excep
  0.71    800.31     6.78 84209013     0.00     *my_subprogram*
  0.63    806.36     6.05                             malloc



    I'm new to Ada, and afraid I may have inadvertantly used the
language in an improper fashion, resulting in poor performance.
My thanks to anyone who can enlighten me as to what might be done to
eliminate any unnecessary performance overhead.


regards,

Charles.