RE: [PATCH] general config option cleanup

From: Luck, Tony <tony.luck_at_intel.com>
Date: 2004-09-09 08:11:16
>I don't really like this.  It penalises platforms like Intel's 
>Tiger box that have contiguous memory.  I'd really like to
>see VIRTUAL_MEM_MAP go away and the DISCONTIGMEM code be
>usable for both zx1/sx1000 and sn2.

Caveat: I haven't read all of Jesse's patch yet.

CONFIG_VIRTUAL_MEM_MAP isn't entirely accurately named.  It
*used* to enable the virtual mem_map, but quite a while ago
the code was changed so that even if VIRTUAL_MEM_MAP was set,
you would only actually use a virtual mem_map if you had big
holes in your physical address space.  See the:

	if (max_gap < LARGE_GAP)

in arch/ia64/mm/contig.c

Also ... Tiger systems only have contiguous physical memory
if they have <= 2GB.  There is a hole in the physical address
space from 2G to 4G to make space for memory mapped I/O devices.

-Tony

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Received on Wed Sep 8 18:13:31 2004

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