Performance: Using coz to point out hot spots

General
1

I just ran into this interesting benchmarking program:

I ran it on swipl (I think I did this a couple of times to get an 80MB profile.coz file, took about two hours, maybe more):

$ cd /tmp/swipl-devel/bench
$ for i in $(seq 330); do coz run -b /tmp/swipl-devel/build.release/%  --- swipl run.pl; done

I placed a throughput benchmark in function PL_next_solution(...) in pl-wam.c (you need to #include “coz.h”):

int
PL_next_solution(qid_t qid)
{ GET_LD
  register_file REGISTERS = {.qid = qid};	/* Active registers */
  Code PC;					/* program counter */
  exception_frame THROW_ENV;			/* PL_thow() environment */

	COZ_PROGRESS;   // <---- Here, this is a counter


#if O_VMI_FUNCTIONS
  register_file *registers = &REGISTERS;

#else /* O_VMI_FUNCTIONS */
...

I got some interesting results after running for perhaps a couple of hours:

coz1
coz1731×756 41.5 KB

I chose “impact” as the sorting mode for the graphs, which come from uploading the profile.coz file to this website: coz plot

  • The first graph says that if line 197 in pl-index.c is sped up by 23% then PL_next_solution(..) will be reached 90% more times per second!
  • The second graph says that if line 2497 in pl-vmi.c is sped up by 55% then PL_next_solution(..) will be reached 55% more times per second!
  • The eighth graph, biggest bang for the buck, says that if line 1939 in pl-vmi.c is sped up by 10% then PL_next_solution(..) will be reached 56% more times per second!

And so on.
If you sort graphics by Min. speedup you get this:

coz2
coz2723×571 26.8 KB

  • The fifth graph says that if you speed up line 509 of pl-inline.h by 50% you will slow down the throughput of PL_next_solution(...) by 26%.

Now that is quite a great benchmarking software. They were able to speedup SQLite by 25% with this tool. You can see more about its operating methods here (I think this is one of the authors):

I figured this may help @dmchurch in his optimization efforts.

I placed the COZ_PROGRESS counter in PL_next_solution(..) because that is where we get the answer after calling a predicate.

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2

Oh wow, this is REALLY cool! I’m definitely going to be checking this out. (Also, it took me around three or four rereads to realize this said “causal” profiling and not “casual”… :sweat_smile:)

Oh, and fyi, it’s “their” (or “her”, if necessary). Anyway, thanks so much for the tip! I can’t wait to get the refactors I’m doing out of the way so I can start playing around with this :smile:

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