linux-kernel - [PATCH v2 5/5] mm: page_alloc: reduce unnecessary binary search in early_pfn

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Message-Id: <1521894282-6454-6-git-send-email-hejianet@gmail.com>
Date:   Sat, 24 Mar 2018 05:24:42 -0700
From:   Jia He <hejianet@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Mel Gorman <mgorman@...e.de>,
        Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>
Cc:     Pavel Tatashin <pasha.tatashin@...cle.com>,
        Daniel Jordan <daniel.m.jordan@...cle.com>,
        AKASHI Takahiro <takahiro.akashi@...aro.org>,
        Gioh Kim <gi-oh.kim@...fitbricks.com>,
        Steven Sistare <steven.sistare@...cle.com>,
        Daniel Vacek <neelx@...hat.com>,
        Eugeniu Rosca <erosca@...adit-jv.com>,
        Vlastimil Babka <vbabka@...e.cz>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, James Morse <james.morse@....com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Steve Capper <steve.capper@....com>, x86@...nel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Philippe Ombredanne <pombredanne@...b.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Kemi Wang <kemi.wang@...el.com>,
        Petr Tesarik <ptesarik@...e.com>,
        YASUAKI ISHIMATSU <yasu.isimatu@...il.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Nikolay Borisov <nborisov@...e.com>,
        Jia He <hejianet@...il.com>, Jia He <jia.he@...-semitech.com>
Subject: [PATCH v2 5/5] mm: page_alloc: reduce unnecessary binary search in early_pfn_valid()

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 if 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@...-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 0bb0274..68aef71 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -5484,8 +5484,8 @@ 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 (defined CONFIG_HAVE_MEMBLOCK) && (defined CONFIG_HAVE_ARCH_PFN_VALID)
+		if (!early_pfn_valid(pfn, &idx)) {
 			/*
 			 * Skip to the pfn preceding the next valid one (or
 			 * end_pfn), such that we hit a valid pfn (or end_pfn)
-- 
2.7.4