Re: [patch 2] mm: speculative get_page

[Andy Whitcroft]

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
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