Re: pte-highmem-5

Rik van Riel
2002-01-16T19:34:56Z

On Wed, 16 Jan 2002, Linus Torvalds wrote:

> - do the highmem pte bouncing only for CONFIG_X86_PAE: with less then 4GB
> of RAM this doesn't seem to matter all that much (rule of thumb: we
> need about 1% of memory for page tables).

Actually, with 100 processes mapping a 1 GB area of shared
memory, you'll need about 100 MB of page tables or 10% of
the SHM segment. This rises even further with PAE and/or
more processes.

The page table cost for heavily shared memory segments is
really getting out of hand, IMHO ... it might be worth it
to set aside a separate memory zone and use 4 MB pages for
the SHM segment.

regards,

Rik
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