Re: [RFC] non-refcounted pages, application to slab?

From: Nick Piggin
Date: Wed Jan 25 2006 - 05:58:51 EST


On Wed, Jan 25, 2006 at 12:30:03PM +0200, Pekka Enberg wrote:
> Hi Nick,
>
> On 1/25/06, Nick Piggin <npiggin@xxxxxxx> wrote:
> > This is probably not worthwhile for most cases, but slab did strike me
> > as a potential candidate (however the complication here is that some
> > code I think uses the refcount of underlying pages of slab allocations
> > eg nommu code). So it is not a complete patch, but I wonder if anyone
> > thinks the savings might be worth the complexity?
> >
> > Is there any particular code that is really heavy on slab allocations?
> > That isn't mostly handled by the slab's internal freelists?
>
> I certainly hope not. For heavy users, the slab allocator should grow
> caches enough to satisfy most allocations from the them. Also, I think

I figured this would usually be the case.

> we want to keep the reference counting for slab pages so that we can
> use kmalloc'd memory in the block layer.
>

Does that happen now? Where is it needed (nbd or something I guess?)

Nick

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