Re: mem_map

From: David Mosberger <davidm_at_napali.hpl.hp.com>
Date: 2005-05-09 23:31:45
>>>>> On Fri, 6 May 2005 19:59:59 +0530, Vaibhav Sharma <vaibhav.sh@gmail.com> said:

  Vaibhav> hi all, Can any body provide any information for the
  Vaibhav> significance of "CONFIG_VIRTUAL_MEM_MAP"?

Turning on this option puts the Linux physical memory-map (mem_map)
into virtual memory rather than physical memory.  Doing so can be an
advantage on machines which have holes in the physical memory.  For
example, on zx1-based machines, physical memory 1GB-4GB shows up at an
address above 257GB so there is a hole of about 256GB below that
address.

There are other ways to manage (huge) holes in physical memory space,
but with the large page-sizes (64MB or 16MB) we use on ia64 for
identity-mapping kernel space, this approach seems to work quite well.

	--david
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Received on Mon May 9 09:31:56 2005

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