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authorBob Picco <bob.picco@hp.com>2005-09-03 15:54:26 -0700
committerLinus Torvalds <torvalds@evo.osdl.org>2005-09-05 00:05:38 -0700
commit802f192e4a600f7ef84ca25c8b818c8830acef5a (patch)
tree51e9a6ed164e6a2d8741af510c3954ad79bf19af /include/linux
parent0216f86dafb389c0ad97529fd45e64e883298cfd (diff)
[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>
Diffstat (limited to 'include/linux')
-rw-r--r--include/linux/mmzone.h30
1 files changed, 28 insertions, 2 deletions
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 6c90461ed99..b97054bbc39 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -487,6 +487,28 @@ struct mem_section {
unsigned long section_mem_map;
};
+#ifdef CONFIG_ARCH_SPARSEMEM_EXTREME
+/*
+ * Should we ever require GCC 4 or later then the flat array scheme
+ * can be eliminated and a uniform solution for EXTREME and !EXTREME can
+ * be arrived at.
+ */
+#define SECTION_ROOT_SHIFT (PAGE_SHIFT-3)
+#define SECTION_ROOT_MASK ((1UL<<SECTION_ROOT_SHIFT) - 1)
+#define SECTION_TO_ROOT(_sec) ((_sec) >> SECTION_ROOT_SHIFT)
+#define NR_SECTION_ROOTS (NR_MEM_SECTIONS >> SECTION_ROOT_SHIFT)
+
+extern struct mem_section *mem_section[NR_SECTION_ROOTS];
+
+static inline struct mem_section *__nr_to_section(unsigned long nr)
+{
+ if (!mem_section[SECTION_TO_ROOT(nr)])
+ return NULL;
+ return &mem_section[SECTION_TO_ROOT(nr)][nr & SECTION_ROOT_MASK];
+}
+
+#else
+
extern struct mem_section mem_section[NR_MEM_SECTIONS];
static inline struct mem_section *__nr_to_section(unsigned long nr)
@@ -494,6 +516,10 @@ static inline struct mem_section *__nr_to_section(unsigned long nr)
return &mem_section[nr];
}
+#define sparse_index_init(_sec, _nid) do {} while (0)
+
+#endif
+
/*
* We use the lower bits of the mem_map pointer to store
* a little bit of information. There should be at least
@@ -513,12 +539,12 @@ static inline struct page *__section_mem_map_addr(struct mem_section *section)
static inline int valid_section(struct mem_section *section)
{
- return (section->section_mem_map & SECTION_MARKED_PRESENT);
+ return (section && (section->section_mem_map & SECTION_MARKED_PRESENT));
}
static inline int section_has_mem_map(struct mem_section *section)
{
- return (section->section_mem_map & SECTION_HAS_MEM_MAP);
+ return (section && (section->section_mem_map & SECTION_HAS_MEM_MAP));
}
static inline int valid_section_nr(unsigned long nr)