Re: [PATCH 0/4] V3 ia64 SPARSEMEM

[Greg Edwards <edwardsg@sgi.com>]

On Thu, Jun 16, 2005 at 09:28:19AM -0400, Bob Picco wrote:
| Tony,
| 
| ChangeLog V2:
| 	Jesse's review input has been applied to patches 3 and 4.
| 	These were all cosmetic changes.
| ChangeLog V3:
| 	This patchset has changes for building ia64 with SPARSEMEM +
| 	ARCH_SPARSEMEM_EXTREME config options.  The configuration options
| 	SECTION_BITS and PHYSICAL_MEMORY_BITS have been removed and are
| 	like other arches (not configurable).  
| 
| 	This patchset depends on SPARSEMEM EXTREME patches submitted to -mm.
| 	The -mm patch sparsemem-extreme.patch and all those which it depends
| 	on are required. EXTREME has introduced a two dimensional array
| 	to SPARSEMEM. The two level layout should reduce memory requirements
| 	for extremely sparse memory at the expense of an additional load
| 	and shift when fetching the section map for a page frame.
| 
| 	The only C code change since V2 is in patch 4.  SPARSEMEM's 
| 	routine memory_present, for identifying a section with memory, is
| 	called in paging_init instead of find_memory. This is required
| 	because EXTREME uses the bootmem allocator for the root level
| 	allocations in the new two level layout scheme. 
| 	
| 	I have gathered OSDL aim7 data on an rx2600 4Gb of memory and two
| 	CPUs.  The data is for SPARSEMEM+EXTREME and DISCONTIG+VIRTUAL_MEM_MAP.
| 	This obviously isn't conclusive data for the adoption of ia64
| 	SPARSEMEM but does demonstrate no degradation on a small server.  I'll 
| 	need Jack's help to gather more supporting performance data.
| 
| This is a series of patches which enable SPARSEMEM for ia64.  It's against
| rc4-mm2.  The patches have been tested against memory configurations FLATMEM,
| DISCONTIG and SPARSEMEM+EXTREME.  This includes NUMA simulated hardware, rx2600
| and HPSIM.  An early version of ia64 with SPARSEMEM was tested by Jesse. It
| would be optimal to have another test pass on SGI NUMA hardware.

Bob,

I did a few aim7 runs of SPARSEMEM+EXTREME vs DISCONTIG+VIRTUAL_MEM_MAP
with 2.6.12-mm1 on a 128p Altix.  There wasn't a noticeable difference
between the two, so I think we're good to go.

Greg