Re: [Sbcl-help] Garbage collection for server with user sessions

[Nikodemus S. <nik...@ra...>]

On 27 February 2010 16:46, Brett van de Sande <bv...@as...> wrote:

> If I recompile with a larger value of gencgc-page-bytes, as suggested
> then gc overall becomes *much* slower.

What about adjusting the max_map_count?

> What about doing a gc that only does generation 5?
> That is, put a switch in garbage_collect so that, if desired, it only
> calls  garbage_collect_generation(5,0)

The way the GC works is that you cannot collect generation N+1 unless
generation N is empty -- so no. This is a fairly fundamental
assumption in the system.

> OK, I understand that there is no lisp version of free().
> However, would it help the garbage collection if I applied
> something like the following to my session data at the close
> of a session:
>
> (defun dereference (obj)
>       (cond ((consp obj)
>              (dereference (car obj))
>              (dereference (cdr obj))
>              (setf (car obj) nil)
>              (setf (cdr ojb) nil))
>        ;; add similar actions for arrays, structs, etc.
> ))

To a degree, yes.

Doing it always for everything is almost certainly a bad idea, but
doing things like CLRHASH for hash-tables or FILL for vectors can be
worthwhile.

It all depends: if cleaning out pointers means you're writing to
write-protected pages it is going to be a loss -- but if those pages
are dirty already, it is probably a win.

Cheers,

 -- Nikodemus