Re: munmap extremely slow even with untouched mapping.

[Nick Piggin]

Hugh Dickins wrote:

> Yes, it's a good observation from Robin.
>
> It'll have been spoiling the exit speedup we expected from your
> 2.6.14 copy_page_range "Don't copy [faultable] ptes" fork speedup.

Yep. Not to mention it is probably responsible for some of the
4 level page table performance slowdowns on x86-64.

> I prefer your patch too.  But I'm not very interested in temporary
> speedups relative to 2.6.14.  Attacking this is a job I'd put off
> until after the page fault scalability changes, which make it much
> easier to do a proper job.

Yeah definitely.

I wonder if we should go with Robin's fix (+/- my variation)
as a temporary measure for 2.6.15?

--
SUSE Labs, Novell Inc.

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