[ccan] New module: rprof, runtime profiler/timers

[Rusty Russell]

On Fri, 26 Aug 2011 22:03:45 +0200, Christian Thaeter <ct at pipapo.org> wrote:
> Some observations: It is a bit exceptional as I designed it not to
code, I think.

> This possibly could
> improved with asserts or runtime checks, but I strive to make the
> timer function as deterministic AND small as possible. This makes
> writing tests a bit superfluous.

Err, no it doesn't!

Even a very simple program which mallocs a struct rprof, calls
rprof_init(), runs rprof_start() then rprof_stop(), then tests that
rprof_sum() >= 0 will test that you initialize all the fields correctly
(since it's run under valgrind).

Other suggestions:

1) Split the benchmark stuff into rprof_bench.h?
2) Use ccan/time?
3) Something to avoid compiler elimination of code, such as an
   enhancement to RPROF_BENCH* which make sure gcc thinks it needs
   the result?
4) #if HAVE_FOR_LOOP_DECLARATION || RPROF_STDC_VERSION >= 199901L
   is ugly.  Preferred is to include "config.h", maybe like:

        #if 1 /* If you have a config.h, eg in ccan */
        #include "config.h"
        #else
        # if __STDC_VERSION__ >= 199901L
        #  define HAVE_FOR_LOOP_DECLARATION 1
        # endif
        #endif

   Though hacking up a config.h is expected abilities for someone using
   ccan.
5) Your documentation style manages to be nonstandard *and* ugly,
   but I'm sure you know that :)

> * How to disable valgrind for ccanlint testing?

(I answered this on IRC, but repeating here for posterity):

As a once-off:

   ccanlint -x run_tests_valgrind

To suppress it in general, use _info.  Either per-test:

 * Ccanlint:
 *	// valgrind breaks on setsched().
 *	tests_pass_valgrind test/run.c:FAIL

Or to add some args to the valgrind cmdline:
        
 * Ccanlint:
 *	// valgrind breaks on setsched().
 *	tests_pass_valgrind test/run.c:--args

Without the "testname:" prefix, it applies to all the tests.

> * This needs '-lrt' any way to put that in the metadata?

Yep! _info can tell what libraries to use:
	if (strcmp(argv[1], "libs") == 0) {
		printf("rt\n");
		return 0;
        }	

It can depend on config.h #ifdefs, but I wouldn't worry about that until
someone ports it and fails...

Thanks!
Rusty.