Re: Threads performance issue.

[Sylvain Le Gall <sylvain@le-gall.net>]

On 17-02-2009, Rémi Dewitte <remi@gide.net> wrote:
>
> test.csv is a 21mo file with ~13k rows and a thousands of columns on a 15rp=
> m
> disk.
>
> ocaml version : 3.11.0
>

You are using input_char and standard IO channel. This is a good choice
for non-threaded program. But in your case, I will use Unix.read with a
big buffer (32KB to 4MB) and change your program to use it. As
benchmarked by John Harrop, you are spending most of your time in
caml_enter|leave_blocking section. I think it comes from reading using
std IO channel which use 4k buffer. Using a bigger buffer will allow
less call to this two functions (but you won't win time at the end, I
think you will just reduce the difference between non-threaded and
threaded code).

Regards
Sylvain Le Gall