[PATCH] SPARSEMEM EXTREME

A new option for SPARSEMEM is ARCH_SPARSEMEM_EXTREME.  Architecture
platforms with a very sparse physical address space would likely want to
select this option.  For those architecture platforms that don't select the
option, the code generated is equivalent to SPARSEMEM currently in -mm.
I'll be posting a patch on ia64 ml which uses this new SPARSEMEM feature.

ARCH_SPARSEMEM_EXTREME makes mem_section a one dimensional array of
pointers to mem_sections.  This two level layout scheme is able to achieve
smaller memory requirements for SPARSEMEM with the tradeoff of an
additional shift and load when fetching the memory section.  The current
SPARSEMEM -mm implementation is a one dimensional array of mem_sections
which is the default SPARSEMEM configuration.  The patch attempts isolates
the implementation details of the physical layout of the sparsemem section
array.

ARCH_SPARSEMEM_EXTREME depends on 64BIT and is by default boolean false.

I've boot tested under aim load ia64 configured for ARCH_SPARSEMEM_EXTREME.
 I've also boot tested a 4 way Opteron machine with !ARCH_SPARSEMEM_EXTREME
and tested with aim.

Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Bob Picco <bob.picco@hp.com>
Signed-off-by: Dave Hansen <haveblue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 22 insertions, 0 deletions

diff --git a/include/asm-ppc64/lmb.h b/include/asm-ppc64/lmb.h
index cb368bf0f264..de91e034bd98 100644
--- a/include/asm-ppc64/lmb.h
+++ b/include/asm-ppc64/lmb.h
@@ -56,4 +56,26 @@ extern void lmb_dump_all(void);
 
 extern unsigned long io_hole_start;
 
+static inline unsigned long
+lmb_size_bytes(struct lmb_region *type, unsigned long region_nr)
+{
+        return type->region[region_nr].size;
+}
+static inline unsigned long
+lmb_size_pages(struct lmb_region *type, unsigned long region_nr)
+{
+        return lmb_size_bytes(type, region_nr) >> PAGE_SHIFT;
+}
+static inline unsigned long
+lmb_start_pfn(struct lmb_region *type, unsigned long region_nr)
+{
+        return type->region[region_nr].base >> PAGE_SHIFT;
+}
+static inline unsigned long
+lmb_end_pfn(struct lmb_region *type, unsigned long region_nr)
+{
+        return lmb_start_pfn(type, region_nr) +
+               lmb_size_pages(type, region_nr);
+}
+
 #endif /* _PPC64_LMB_H */