[Bochs-developers] bochs profiling data

[Bryce D. <br...@tl...>]

I just learned how to use gcc's profiling and code coverage tools, gprof
and gcov.  Here is a sample.

This data was collected during a boot of DLX Linux, about 70 million
instructions.  You can see which functions are taking up the most time
during the process.  I made this table by compiling with "gcc -pg",
running bochs, and then running gprof.

I hope that since FetchDecode represents such a large chunk of the
execution time, we can find ways to improve it.  I imagine this code is a
branch prediction killer.  Maybe it would help to rewrite it a few
function pointers and a lot fewer switch() statements.  And maybe we can
store the FetchDecode results for frequently used instructions.

[NOTE: tick1 includes handling of all timer triggered devices, such as
PIT, keyboard, vga, etc.  access_linear and read_physical are memory
accesses.  dtranslate_linear is paging table lookups.]

  %
 time   seconds    calls    name
 26.04    17.73 69621020    bx_cpu_c::FetchDecode(unsigned
 14.36     9.78        1    bx_cpu_c::cpu_loop(int)
  5.79     3.94 79245500    bx_pc_system_c::tick1(void)
  5.11     3.48 32099404    bx_cpu_c::access_linear(unsigne
  3.48     2.37 19909598    bx_cpu_c::dtranslate_linear(uns
  3.10     2.11  1685669    bx_pc_system_c::timer_handler(v
  2.89     1.97 10644497    bx_cpu_c::JCC_Jd(BxInstruction_
  2.63     1.79 22066173    bx_mem_c::read_physical(bx_cpu_
  2.61     1.78 47864644    bx_cpu_c::protected_mode(void)
  2.61     1.78 18759040    bx_cpu_c::read_virtual_checks(b
  2.23     1.52 13772454    bx_cpu_c::read_virtual_dword(un
  1.91     1.30 13385236    bx_cpu_c::write_virtual_checks(
  1.25     0.85 13371896    bx_mem_c::write_physical(bx_cpu
  1.19     0.81  7676838    bx_cpu_c::write_virtual_dword(u
  1.07     0.73  7812930    bx_cpu_c::get_ZF(void)
  0.97     0.66  6157217    bx_cpu_c::MOV_GdEd(BxInstructio
  0.75     0.51  6095406    bx_cpu_c::revalidate_prefetch_q
  0.75     0.51  3785671    bx_cpu_c::CMP_EdGd(BxInstructio
  0.73     0.50   790981    bx_hard_drive_c::read_handler(v
  0.54     0.37  4335024    bx_cpu_c::push_32(unsigned int)


The code coverage data was too big to post here, but you can see it all at
http://bochs.sf.net/tmp/profiling


-Bryce