On Fri, 18 May 2007, Nick Piggin wrote:
quoted text
> 
> If we add 8 bytes to struct page on 64-bit machines, it becomes 64 bytes,
> which is quite a nice number for cache purposes.
> 
> However we don't have to let those 8 bytes go to waste: we can use them
> to store the virtual address of the page, which kind of makes sense for
> 64-bit, because they can likely to use complicated memory models.

Sooner rather than later, don't we need those 8 bytes to expand from
atomic_t to atomic64_t _count and _mapcount?  Not that we really need
all 64 bits of both, but I don't know how to work atomically with less.

(Why do I have this sneaking feeling that you're actually wanting
to stick something into the lower bits of page->virtual?)

Hugh
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