Re: [patch 2] mm: speculative get_page

Andy Whitcroft
2005-06-28T12:45:22Z

Nick Piggin wrote:

> #define PG_free 20 /* Page is on the free lists */
> +#define PG_freeing 21 /* PG_refcount about to be freed */

Wow this needs two new page bits. That might be a problem ongoing.
There are only 24 of these puppies and this takes us to just two
remaining. Do we really need _two_ to track free?

One obvious area of overlap might be the PG_nosave_free which seems to
be set on free pages for software suspend. Perhaps that and PG_free
will be equivalent in intent (though maintained differently) and allow
us to recover a bit?

There are a couple of bits which imply ownership such as PG_slab,
PG_swapcache and PG_reserved which to my mind are all exclusive.
Perhaps those plus the PG_free could be combined into a owner field. I
am unsure if the PG_freeing can be 'backed out' if not it may also combine?

Mumble ...

-apw