Non-zero CPU usage when using threads

Hi,

I've been surprised to see my app use 1% - 2% of my CPU. I've reduced
the test case down to:
  let () = GtkThread.main ()

Compiled with:
  ocamlcp -I /ocaml/lib/ocaml/std-lib/threads -I
/ocaml/lib/ocaml/pkg-lib/lablgtk2 unix.cma threads.cma lablgtk.cma
gtkThread.cmo -p a cpu.ml

I found that by editing gtkThread.ml, I could lower the cpu usage:
    -      Thread.delay 0.001;
  +      Thread.delay 0.013;

I've put a local copy of gtkThread.ml with the aforementioned change
in my  code (I'm not sure it's ok license-wise but currently caravel's
license is almost left unspecified) [1]. I'd like comments on this:
how is it, any good/better solution?

[1] http://git.ocamlcore.org/cgi-bin/gitweb.cgi?p=caravel/caravel.git;a=commitdiff;h=81e7a6c32dcc72eadb4233f7d08b1d5885a455c8