linux-kernel - [PATCH v9 6/6] mm: page_alloc: reduce unnecessary binary search in early_pfn

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Date:   Fri, 29 Jun 2018 10:29:23 +0800
From:   Jia He <hejianet@...il.com>
To:     Russell King <linux@...linux.org.uk>,
        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>,
        "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>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        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>, richard.weiyang@...il.com,
        Jia He <hejianet@...il.com>, Jia He <jia.he@...-semitech.com>
Subject: [PATCH v9 6/6] 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 whether pfn++ is still in the same
region.

Currently it only improve the performance on arm/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 27956us to 13537us in my
armv8a server(QDF2400 with 96G memory, pagesize 64k).

Signed-off-by: Jia He <jia.he@...-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 57cdc42..ac34238 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1267,11 +1267,16 @@ 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_MEMBLOCK_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)
-- 
1.8.3.1