Re: [PATCH] GFP_THISNODE for the slab allocator

[Andrew Morton <akpm@osdl.org>]

On Fri, 15 Sep 2006 00:23:25 -0700
Andrew Morton <akpm@osdl.org> wrote:

> 
> There are two problems:
> 
> a) the linear search across nodes which are not in the cpuset
> 
> b) the linear search across nodes which _are_ in the cpuset, but which
>    are used up.
> 
> I'm thinking a) is easily solved by adding an array of the zones inside the
> `struct cpuset', and change get_page_from_freelist() to only look at those
> zones.
> 
> And b) can, I think, be solved by caching the most-recently-allocated-from
> zone* inside the cpuset as well.  This might alter page allocation
> behaviour a bit.  And we'd need to do an exhaustive search at some point in
> there.

err, if we cache the most-recently-allocated-from zone in the cpuset then
we don't need the array-of-zones, do we?  We'll only need to do a zone
waddle when switching from one zone to the next, which is super-rare.

That's much simpler.

> The nasty part is locking that array of zones, and its length, and the
> cached zone*.  I guess it'd need to be RCUed.

And locking becomes simpler too.  It's just a check of
cpuset_zone_allowed(current->cpuset->current_allocation_zone), in
get_page_from_freelist(), isn't it?


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