Re: test13-pre5

From: Mark Hemment (
Date: Fri Dec 29 2000 - 12:54:36 EST

On Fri, 29 Dec 2000, Tim Wright wrote:
> Yes, this is a very important point if we ever want to make serious use
> of large memory machines on ia32. We ran into this with DYNIX/ptx when the
> P6 added 36-bit physical addressing. Conserving KVA (kernel virtual address
> space), became a very high priority. Eventually, we had to add code to play
> silly segment games and "magically" materialize and dematerialize a 4GB
> kernel virtual address space instead of the 1GB. This only comes into play
> with really large amounts of memory, and is almost certainly not worth the
> agony of implementation on Linux, but we'll need to be careful elsewhere to
> conserve it as much as possible.

  Indeed. I'm compiling my kernels with 2GB virtual. Not as I want more
NORMAL pages in the page cache (HIGH memory is fine), but as I need
NORMAL pages for kernel data/structures (memory allocated from
slab-caches) which need to be constantly mapped in.


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