Re: [Caml-list] Slow GC problem

[David Monniaux <monniaux@dmi.ens.fr>]

On Mon, 7 Apr 2003, Chris Hecker wrote:

> >I am concluding that gc is to blame.
> Did you profile to check this assumption?  What's the profile look like?

A little bit of experience here: I have done such profiles with the
following tools:

* gprof (compile with ocamlopt -p and gcc -pg);

* oprofile (hardware-based, supports only certain platforms including
  Linux/x86; can profile not only clock ticks, but also events such as
  cache faults).

My (somehow unsurprising) experience was that:
* GC generates 15-20% of cache faults
* GC takes about 15% of time.
A conjecture on my part is that using a lot of unboxed floats is partly
responsible.

My conclusion: you should definitely profile your code before starting
to incriminate the GC or any other module.


David Monniaux            http://www.di.ens.fr/~monniaux
Laboratoire d'informatique de l'École Normale Supérieure,
Paris, France

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