[PATCH v4 5/5] 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(), if pfn and
pfn+1 are in the same memblock region, we can record the last returned
memblock region index and check check pfn++ is still in the same region.

Currently it only improve the performance on arm64 and will have no
impact on other arches.

Signed-off-by: Jia He <jia.he@xxxxxxxxxxxxxxxx>
---
 include/linux/mmzone.h | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index d797716..b68d22c 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1267,9 +1267,14 @@ 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) pfn_valid_region(pfn, &early_region_idx)
+#else
 #define early_pfn_valid(pfn)	pfn_valid(pfn)
+#endif /*CONFIG_HAVE_ARCH_PFN_VALID*/
+
 void sparse_init(void);
 #else
 #define sparse_init()	do {} while (0)
-- 
2.7.4