[PATCH 4/4] mm: page_alloc: reduce unnecessary binary search in early_pfn_valid()

[Jia He]

Commit b92df1de5d28 ("mm: page_alloc: skip over regions of invalid pfns
where possible") optimized the loop in memmap_init_zone(). But there is
still some room for improvement. E.g. in early_pfn_valid(), we can record
the last returned memblock region index and check check pfn++ is still in
the same region.

Currently it only improves the performance on arm64 and has no impact on
other arches.

Signed-off-by: Jia He <jia...@hxt-semitech.com>
---
 arch/x86/include/asm/mmzone_32.h |  2 +-
 include/linux/mmzone.h           | 12 +++++++++---
 mm/page_alloc.c                  |  2 +-
 3 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/mmzone_32.h b/arch/x86/include/asm/mmzone_32.h
index 73d8dd1..329d3ba 100644
--- a/arch/x86/include/asm/mmzone_32.h
+++ b/arch/x86/include/asm/mmzone_32.h
@@ -49,7 +49,7 @@ static inline int pfn_valid(int pfn)
        return 0;
 }
 
-#define early_pfn_valid(pfn)   pfn_valid((pfn))
+#define early_pfn_valid(pfn, last_region_idx)  pfn_valid((pfn))
 
 #endif /* CONFIG_DISCONTIGMEM */
 
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index d797716..3a686af 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1267,9 +1267,15 @@ static inline int pfn_present(unsigned long pfn)
 })
 #else
 #define pfn_to_nid(pfn)                (0)
-#endif
+#endif /*CONFIG_NUMA*/
+
+#ifdef CONFIG_HAVE_ARCH_PFN_VALID
+#define early_pfn_valid(pfn, last_region_idx) \
+                               pfn_valid_region(pfn, last_region_idx)
+#else
+#define early_pfn_valid(pfn, last_region_idx)  pfn_valid(pfn)
+#endif /*CONFIG_HAVE_ARCH_PFN_VALID*/
 
-#define early_pfn_valid(pfn)   pfn_valid(pfn)
 void sparse_init(void);
 #else
 #define sparse_init()  do {} while (0)
@@ -1288,7 +1294,7 @@ struct mminit_pfnnid_cache {
 };
 
 #ifndef early_pfn_valid
-#define early_pfn_valid(pfn)   (1)
+#define early_pfn_valid(pfn, last_region_idx)  (1)
 #endif
 
 void memory_present(int nid, unsigned long start, unsigned long end);
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index f28c62c..215dc92 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5481,7 +5481,7 @@ void __meminit memmap_init_zone(unsigned long size, int 
nid, unsigned long zone,
                if (context != MEMMAP_EARLY)
                        goto not_early;
 
-               if (!early_pfn_valid(pfn)) {
+               if (!early_pfn_valid(pfn, &idx)) {
 #ifdef CONFIG_HAVE_MEMBLOCK
                        /*
                         * Skip to the pfn preceding the next valid one (or
-- 
2.7.4