Re: [PATCH] low-latency zap_page_range()

From: Rik van Riel (riel@conectiva.com.br)
Date: Thu Aug 29 2002 - 16:46:15 EST

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On Thu, 29 Aug 2002, Andrew Morton wrote:

> > So we know it is held forever and a day... but is there contention?
>
> I'm sure there is, but nobody has measured the right workload.
>
> Two CLONE_MM threads, one running mmap()/munmap(), the other trying
> to fault in some pages. I'm sure someone has some vital application
> which does exactly this. They always do :(

Can't fix this one. The mmap()/munmap() needs to have the
mmap_sem for writing as long as its setting up or tearing
down a VMA while the pagefault path takes the mmap_sem for
reading.

It might be fixable in some dirty way, but I doubt that'll
ever be worth it.

regards,

Rik

-- Bravely reimplemented by the knights who say "NIH".

http://www.surriel.com/ http://distro.conectiva.com/

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