Matthew Dillon wrote:
> Hmm. I'm fairly sure that Linux does not quite do it that way. I
> believe the 2-level page tables are copy-on-write, but that only
> gives you shareability across a fork() and then only for a little
> while. I'm fairly certain that Linux cannot share page tables
> for post-fork modifications (like when you mmap() or get a SysV
> shared segment). The rmap patches are roughly equivalent to our
> i386 pmap code and allow Rik to implement page queues and proper page
> aging.
I wasn't saying that they were shared on the mmap(); Peter had
suggested it for FreeBSD.
Also "a little while" is relative; as long as you don't write
the page, it should stay shared. That basically means that all
instances of apache share mappings on the code pages.
Here's the article I was reading in one window while typing in the
other. It's linked off the article reference I posted to -arch
earlier:
http://old.lwn.net/2002/0124/kernel.php3
"What Rik van Riel is up to."
FWIW: In the original Article:
http://lwn.net/Articles/3327/
they say they've gon to a 3 level page table scheme for the Hammer
port.
-- Terry
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