Re: 2.5.68-mm2

Benjamin LaHaise (bcrl@redhat.com)
Wed, 23 Apr 2003 23:36:52 -0400

On Wed, Apr 23, 2003 at 02:46:48PM -0700, Andrew Morton wrote:
> Ingo-rmap seems a better solution to me. It would be a fairly large change
> though - we'd have to hold the four atomic kmaps across an entire pte page
> in copy_page_range(), for example. But it will then have good locality of
> reference between adjacent pages and may well be quicker than pte_chains.

Actually, Ingo's rmap style sounds very similar to what I first implemented
in one of my stabs at rmap. It has a nasty side effect of being worst case
for cache organisation -- the sister page tends to map to the exact same
cache line in some processors. Whoops. That said, I think that the rmap
pte-chains can really stand a bit of optimization by means of discarding a
couple of bits, as well as merging for adjacent pages, so I don't think
the overhead is a lost cause yet. And nobody has written the clone() patch
for bash yet...

-ben

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