[PATCH] mm: memmap_init_zone() performance improvement

[Mike Yoknis <mike.yoknis@hp.com>]

memmap_init_zone() loops through every Page Frame Number (pfn),
including pfn values that are within the gaps between existing
memory sections.  The unneeded looping will become a boot
performance issue when machines configure larger memory ranges
that will contain larger and more numerous gaps.

The code will skip across invalid sections to reduce the
number of loops executed.

Signed-off-by: Mike Yoknis <mike.yoknis@hp.com>
---
 arch/x86/include/asm/mmzone_32.h     |    2 ++
 arch/x86/include/asm/page_32.h       |    1 +
 arch/x86/include/asm/page_64_types.h |    3 ++-
 include/asm-generic/page.h           |    1 +
 include/linux/mmzone.h               |    6 ++++++
 mm/page_alloc.c                      |    5 ++++-
 6 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/mmzone_32.h b/arch/x86/include/asm/mmzone_32.h
index eb05fb3..73c5c74 100644
--- a/arch/x86/include/asm/mmzone_32.h
+++ b/arch/x86/include/asm/mmzone_32.h
@@ -48,6 +48,8 @@ static inline int pfn_to_nid(unsigned long pfn)
 #endif
 }
 
+#define next_pfn_try(pfn)	((pfn)+1)
+
 static inline int pfn_valid(int pfn)
 {
 	int nid = pfn_to_nid(pfn);
diff --git a/arch/x86/include/asm/page_32.h b/arch/x86/include/asm/page_32.h
index da4e762..e2c4cfc 100644
--- a/arch/x86/include/asm/page_32.h
+++ b/arch/x86/include/asm/page_32.h
@@ -19,6 +19,7 @@ extern unsigned long __phys_addr(unsigned long);
 
 #ifdef CONFIG_FLATMEM
 #define pfn_valid(pfn)		((pfn) < max_mapnr)
+#define next_pfn_try(pfn)	((pfn)+1)
 #endif /* CONFIG_FLATMEM */
 
 #ifdef CONFIG_X86_USE_3DNOW
diff --git a/arch/x86/include/asm/page_64_types.h b/arch/x86/include/asm/page_64_types.h
index 320f7bb..02d82e5 100644
--- a/arch/x86/include/asm/page_64_types.h
+++ b/arch/x86/include/asm/page_64_types.h
@@ -69,7 +69,8 @@ extern void init_extra_mapping_wb(unsigned long phys, unsigned long size);
 #endif	/* !__ASSEMBLY__ */
 
 #ifdef CONFIG_FLATMEM
-#define pfn_valid(pfn)          ((pfn) < max_pfn)
+#define pfn_valid(pfn)		((pfn) < max_pfn)
+#define next_pfn_try(pfn)	((pfn)+1)
 #endif
 
 #endif /* _ASM_X86_PAGE_64_DEFS_H */
diff --git a/include/asm-generic/page.h b/include/asm-generic/page.h
index 37d1fe2..316200d 100644
--- a/include/asm-generic/page.h
+++ b/include/asm-generic/page.h
@@ -91,6 +91,7 @@ extern unsigned long memory_end;
 #endif
 
 #define pfn_valid(pfn)		((pfn) >= ARCH_PFN_OFFSET && ((pfn) - ARCH_PFN_OFFSET) < max_mapnr)
+#define next_pfn_try(pfn)	((pfn)+1)
 
 #define	virt_addr_valid(kaddr)	(((void *)(kaddr) >= (void *)PAGE_OFFSET) && \
 				((void *)(kaddr) < (void *)memory_end))
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index f7d88ba..04d3c39 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1166,6 +1166,12 @@ static inline int pfn_valid(unsigned long pfn)
 		return 0;
 	return valid_section(__nr_to_section(pfn_to_section_nr(pfn)));
 }
+
+static inline unsigned long next_pfn_try(unsigned long pfn)
+{
+	/* Skip entire section, because all of it is invalid. */
+	return section_nr_to_pfn(pfn_to_section_nr(pfn) + 1);
+}
 #endif
 
 static inline int pfn_present(unsigned long pfn)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 5b6b6b1..dd2af8b 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3798,8 +3798,11 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
 		 * exist on hotplugged memory.
 		 */
 		if (context == MEMMAP_EARLY) {
-			if (!early_pfn_valid(pfn))
+			if (!early_pfn_valid(pfn)) {
+				pfn = next_pfn_try(pfn);
+				pfn--;
 				continue;
+			}
 			if (!early_pfn_in_nid(pfn, nid))
 				continue;
 		}
-- 
1.7.1

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