Re: [Caml-list] Ocaml implementation and low level details

[Samuel Thibault <samuel.thibault@inria.fr>]

Konstantin Tcholokachvili, le Thu 28 Jan 2010 14:35:50 +0100, a écrit :
>     > - Also need I disable Ocaml theading subsystem? (Obviously yes, but are
>     there
>     > some limitations?)
> 
>     IIRC we just needed to port it.
> 
> 
> OK but as there is a giant lock (as I heard), I'm afraid that the
> multithreading subsystem of my kernel will suffer from that.
> Am I correct?

Ah, the kernel can't be running concurrently, yes. Just like Linux 2.0
was working, actually.

>     > Are there other important considerations to take?
> 
>     In my memory, mostly the direct access to some kinds of memory, like the
>     video memory: we faked a string with the -unsafe option to get efficient
>     direct access.
> 
> So must I also make tricks to have DMA acess?

Yes, unless you get hooks into the caml runtime to be notified of
garbage collection, to update pointers & such.

>     > Do you think that Ocaml is suitable for OS coding (I''m using C now).
> 
>     It's much better for all the programmability & safety reasons. Funk
>     showed that it is possible. Performance should be quite good.  Now the
>     pragmatic answer would be that Linux already works quite well and has
>     all the drivers we need, while yet another new kernel would have to
>     rewrite them all. And about performance, when you see how much Linux
>     people care about tiny details in their lock implementation etc., a caml
>     implementation wouldn't suit that.
> 
> My goal isn't to have a kenel portable across many platforms but only
> to some kind of hardware.  It's a hobby project.

Ok, then you can probably start with the current funk testbed :)

> Why caml's implementation wouldn't be suitable? Because of the giant lock as I
> mentioned before?

Because you do not have as much control over e.g. data alignment & such
as in C. Linux people spend quite some time fine-tuning such small
details and get performance benefits.

Samuel