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From:   Jia He <hejianet@gmail.com>
To:     Russell King <linux@armlinux.org.uk>,
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        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
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        Jia He <jia.he@hxt-semitech.com>
Subject: [PATCH v6 5/5] mm: page_alloc: reduce unnecessary binary search in early_pfn_valid()
Date:   Tue,  3 Apr 2018 19:56:19 -0700
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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.

For the performance improvement, after this set, I can see the time
overhead of memmap_init() is reduced from 41313 us to 24345 us in my
armv8a server(QDF2400 with 96G memory).

Signed-off-by: Jia He <jia.he@hxt-semitech.com>
---
 include/linux/mmzone.h | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index a517d43..516ffb49 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1271,11 +1271,16 @@ static inline int pfn_present(unsigned long pfn)
 #define pfn_to_nid(pfn)		(0)
 #endif
 
-#define early_pfn_valid(pfn)	pfn_valid(pfn)
 #ifdef CONFIG_HAVE_ARCH_PFN_VALID
 extern ulong memblock_next_valid_pfn(ulong pfn);
 #define next_valid_pfn(pfn)	memblock_next_valid_pfn(pfn)
-#endif
+
+extern int pfn_valid_region(ulong pfn);
+#define early_pfn_valid(pfn)	pfn_valid_region(pfn)
+#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