Re: 2.5.68-mm2

[Benjamin LaHaise <bcrl@redhat.com>]

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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