Re: [Caml-list] Profiling ocaml with lwt

[Adrien Nader <adrien@notk.org>]

Hi,

I tend to (ab)use strace. It has options to only instrument some
syscalls, it can count time spent in syscalls, time spent between
syscalls, has microsecond precision, ...

My first runs are usually "strace -tt -f -o log" to get times with
microseconds, follow forks and write to a file rather than stderr
(heavily advised, especially since text editors have syntax highlighting
for strace's output [ vim at least even though you need to :set
ft=strace when using -tt).

After that, you can also use -T to get the time spent in syscalls, -e to
trace fewer things, ...

It's a hammer and requires a fair bit of eye-crossing but it covers
everything, it's overhead isn't that big and it can easily reduce the
scope of what you need to look more deeply at. However it's probably useless to try
to spend more than 2 hours on a strace's output if you can't find the
answer you're looking for.