8.1 (statprof)

8.1.1 Overview

(statprof) is intended to be a fairly simple statistical profiler for guile. It is in the early stages yet, so consider its output still suspect, and please report any bugs to guile-devel at gnu.org, or to me directly at rlb at defaultvalue.org.

A simple use of statprof would look like this:

       (statprof-reset 0 50000 #t)
       (statprof-start)
       (do-something)
       (statprof-stop)
       (statprof-display)

This would reset statprof, clearing all accumulated statistics, then start profiling, run some code, stop profiling, and finally display a gprof flat-style table of statistics which will look something like this:

       %   cumulative      self              self    total
      time    seconds   seconds    calls  ms/call  ms/call  name
      35.29      0.23      0.23     2002     0.11     0.11  -
      23.53      0.15      0.15     2001     0.08     0.08  positive?
      23.53      0.15      0.15     2000     0.08     0.08  +
      11.76      0.23      0.08     2000     0.04     0.11  do-nothing
       5.88      0.64      0.04     2001     0.02     0.32  loop
       0.00      0.15      0.00        1     0.00   150.59  do-something
      ...

All of the numerical data with the exception of the calls column is statistically approximate. In the following column descriptions, and in all of statprof, "time" refers to execution time (both user and system), not wall clock time.

% time

The percent of the time spent inside the procedure itself (not counting children).

cumulative seconds

The total number of seconds spent in the procedure, including children.

self seconds

The total number of seconds spent in the procedure itself (not counting children).

calls

The total number of times the procedure was called.

self ms/call

The average time taken by the procedure itself on each call, in ms.

total ms/call

The average time taken by each call to the procedure, including time spent in child functions.

name

The name of the procedure.

The profiler uses eq? and the procedure object itself to identify the procedures, so it won't confuse different procedures with the same name. They will show up as two different rows in the output.

Right now the profiler is quite simplistic. I cannot provide call-graphs or other higher level information. What you see in the table is pretty much all there is. Patches are welcome :-)

8.1.2 Implementation notes

The profiler works by setting the unix profiling signal ITIMER_PROF to go off after the interval you define in the call to statprof-reset. When the signal fires, a sampling routine is run which looks at the current procedure that's executing, and then crawls up the stack, and for each procedure encountered, increments that procedure's sample count. Note that if a procedure is encountered multiple times on a given stack, it is only counted once. After the sampling is complete, the profiler resets profiling timer to fire again after the appropriate interval.

Meanwhile, the profiler keeps track, via get-internal-run-time, how much CPU time (system and user – which is also what ITIMER_PROF tracks), has elapsed while code has been executing within a statprof-start/stop block.

The profiler also tries to avoid counting or timing its own code as much as possible.

8.1.3 Usage