Re: Linux 2.4.18pre3-ac1

[Richard Gooch]

Daniel Phillips writes:
> The way I see it, the purpose of lazy page table instantiation is to
> overcome objections to the reverse pte mapping vm technique that
> have been expressed in the past, namely the slowdown in dup_mmap
> inside fork.  I.e., if rmap slows down fork then Linus and Davem are
> going to veto it, as they've done in the past, because they feel
> that the as-yet-unproven advantages of physically-based vm scanning
> doesn't outweigh the easily measurable fork overhead.  Personally, I
> think that's debatable, but by eliminating the overhead we eliminate
> the objection, and as far as I know, it's the only serious
> objection.

Will lazy page table instantiation speed up fork(2) without rmap?
If so, then you've got a problem, because rmap will still be slower
than non-rmap. Linus will happily grab any speedup and make that the
new baseline against which new schemes are compared :-)

				Regards,

					Richard....
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