> The hard limit on VAXen is 24MB of data.  This is because the page
> table design on VAX consumes an incredible amount of memory, so
> increasing it will steal much static allocated memory.

Seems to me the *right* fix for this is to make userland page tables
pageable (or at least swappable).

Of course, that could also run into issues on the KA620.  (Do we
support the KA620 now?  Unfortunately I don't have one on hand.  But I
think this wouldn't make it much worse....)

You could also punch holes on the kernel address space to represent
large holes in the user address space - I think; I forget what happens
if the VM firmware encounters an invalid kernel page when fetching a
PTE for a userland access.  (And actually doing that would be, um,
interesting in its own right.  But it could save memory; you can save
one kernel page, one physical page, for each 64K of invalid userland.)

					der Mouse

			       mouse@rodents.montreal.qc.ca
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