Re: [PATCH 00/28] Swap over NFS -v16

[Pekka Enberg]

Hi Peter,

On Wed, Feb 27, 2008 at 9:58 AM, Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> wrote:
>  > 1/ I note there is no way to tell if memory returned by kmalloc is
>  >   from the emergency reserve - which contrasts with alloc_page
>  >   which does make that information available through page->reserve.
>  >   This seems a slightly unfortunate aspect of the interface.
>
>  Yes, but alas there is no room to store such information in kmalloc().
>  That is, in a sane way. I think it was Daniel Phillips who suggested
>  encoding it in the return pointer by flipping the low bit - but that is
>  just too ugly and breaks all current kmalloc sites to boot.

Why can't you add a kmem_is_emergency() to SLUB that looks up the
cache/slab/page (whatever is the smallest unit of the emergency pool
here) for the object and use that?
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