Re: PXM/Nid/SLIT patch

[David Mosberger <davidm@napali.hpl.hp.com>]

>>>>> On Wed, 18 Feb 2004 17:08:58 +0000, Christoph Hellwig <hch@infradead.org> said:

  Christoph> On Wed, Feb 18, 2004 at 10:33:29AM -0500, Robert Picco wrote:
  >> This PXM value (255) isn't a SLIT or PXM defined quantity.  It is really
  >> specific to HP cell machines.  For example, a machine configured with
  >> two cells will report three PXMs.  Two for the CPUs and one for the
  >> interleaved memory at magic PXM 255.  The firmware doesn't report SLIT
  >> information for PXM 255. The patch approximates the SLIT value for PXM
  >> 255. I have attempted to arrive at code which doesn't break non-HP
  >> hardware configurations. I have assumed the way the initialization code
  >> was written that all NIDs require memory.  Otherwise
  >> reserve_pernode_space will fail.

  Christoph> I know HP basically owns the IA64 ports

This comment concerns me.  I certainly have always tried to judge
patches based on their technical merits for Linux.  Is there anything
in particular that I did (or didn't) do that you found objectionable?
If so, please let me know.

  Christoph> but honestly can't you fix the firmware to return sane
  Christoph> information instead?  i.e. move the above fix to firmware
  Christoph> instead of letting linux fixup the reported data.

Hmmh, I'm no NUMA-expert and it isn't clear to me whether the patch is
working around a firmware-bug or a limitation in the Linux NUMA code.
I don't see off-hand why it should be illegal to have a memory config
with only one node with memory.  The whole PXM_MAGIC business looks
strange to me though.  Can someone explain?

	--david