Re: [hatari-devel] Hatari profiler updates and CPU cycle questions

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Eero,

A high level inspection of cache misses in the BadMood 68030 code (using the profiler post-processing .py script) suggests that it is at least broadly correct. 

There are 2 functions which I pay particular attention to, and one of them has been optimised for cache hits - the other was modified to cause misses deliberately, and this is what I see in the breakdown....



Cache misses:
 28.30%    574172  add_wall_segment     (at 0x14b128)
 22.99%    466446  build_ssector        (at 0x14a6a8)
  7.61%    154432  render_wall_1x1      (at 0x14c616)
  4.61%     93524  cache_resource       (at 0x149c18)
  3.46%     70238  flush_visplanes      (at 0x14a482)
  3.17%     64361  load_real_s_a5_d16_a2        (at 0x14b41a)
  2.24%     45445  invisible    (at 0x14ac88)
  1.94%     39416  nodeincone   (at 0x14ad60)
  1.89%     38376  get_flat_floor       (at 0x14b7de)
  1.89%     38347  render_wall  (at 0x14c5d4)
  1.77%     35818  render_flats_1x1     (at 0x14c128)
  1.76%     35712  process_lighting     (at 0x14d01a)
  1.71%     34652  end_ssector  (at 0x14ac9e)
  1.49%     30164  get_ssector  (at 0x14b704)
  1.41%     28546  new_light_level      (at 0x14d100)
  1.31%     26677  dividing_node        (at 0x14ace6)
  1.27%     25778  ignore_upper (at 0x14ab3c)
  1.20%     24283  finish_tree  (at 0x14a5e4)
  1.18%     23954  add_lower    (at 0x14aa02)
  1.10%     22339  add_upper    (at 0x14aac0)


'render_wall_1x1' has an intensive inner loop which does not fit in the instruction cache, and I expected it to incur the majority of all cache misses (or at the very least, be very high on the list). Interesting that it only rates 7% from the entire group - but it's not impossible.

'render_flats_1x1' is a similar function which is equally intensive - in fact slightly more intensive, but it does fit in the instruction cache, so misses should be minimized.

This does tie up with the .py analysis, which is good!


However I can't say more than this at the moment - it is difficult to tell if the cache miss information is accurate at a per-instruction level or even for small groups of instructions, or whether there are erratic values scattered everywhere and which just happen to 'even out' in long running tests. It will take more time with the code and tests to figure this out. I will try to do this soon.

Regardless, it's already turning into a powerful optimisation tool which I did not have access to before on the Falcon, and it *will* be of use. :-)

D.


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