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From: Jia He <hejianet@gmail.com>
Subject: [PATCH v5 5/5] mm: page_alloc: reduce unnecessary binary search in early_pfn_valid()
Date: Sun,  1 Apr 2018 19:30:36 -0700
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To: Russell King <linux@armlinux.org.uk>, Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will.deacon@arm.com>, Mark Rutland <mark.rutland@arm.com>, Ard Biesheuvel <ard.biesheuvel@linaro.org>, Andrew Morton <akpm@linux-foundation.org>, Michal Hocko <mhocko@suse.com>
Cc: Wei Yang <richard.weiyang@gmail.com>, Kees Cook <keescook@chromium.org>, Laura Abbott <labbott@redhat.com>, Vladimir Murzin <vladimir.murzin@arm.com>, Philip Derrin <philip@cog.systems>, Grygorii Strashko <grygorii.strashko@linaro.org>, AKASHI Takahiro <takahiro.akashi@linaro.org>, James Morse <james.morse@arm.com>, Steve Capper <steve.capper@arm.com>, Pavel Tatashin <pasha.tatashin@oracle.com>, Gioh Kim <gi-oh.kim@profitbricks.com>, Vlastimil Babka <vbabka@suse.cz>, Mel Gorman <mgorman@suse.de>, Johannes Weiner <hannes@cmpxchg.org>, Kemi Wang <kemi.wang@intel.com>, Petr Tesarik <ptesarik@suse.com>, YASUAKI ISHIMATSU <yasu.isimatu@gmail.com>, Andrey Ryabinin <aryabinin@virtuozzo.com>, Nikolay Borisov <nborisov@suse.com>, Daniel Jordan <daniel.m.jordan@oracle.com>, Daniel Vacek <neelx@redhat.com>, Eugeniu Rosca <erosca@de.adit-jv.com>, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Jia He <hejianet@gmail.com>, Jia He <jia.he@hxt-semitech.com>

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@hxt-semitech.com>
---
 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 f9c0c46..079f468 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1268,9 +1268,14 @@ 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)
+#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