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From: Jia He <hejianet@gmail.com>
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>,
	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>
Subject: [PATCH v8 3/6] arm: arm64: page_alloc: reduce unnecessary binary search in memblock_next_valid_pfn()
Date: Wed, 11 Apr 2018 00:21:54 -0700	[thread overview]
Message-ID: <1523431317-30612-4-git-send-email-hejianet@gmail.com> (raw)
In-Reply-To: <1523431317-30612-1-git-send-email-hejianet@gmail.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. if pfn and pfn+1 are in the same
memblock region, we can simply pfn++ instead of doing the binary search
in memblock_next_valid_pfn. Furthermore, if the pfn is in a *gap* of two
memory region, skip to next region directly if possible.

Signed-off-by: Jia He <jia.he@hxt-semitech.com>
---
 include/linux/early_pfn.h | 37 +++++++++++++++++++++++++++++--------
 1 file changed, 29 insertions(+), 8 deletions(-)

diff --git a/include/linux/early_pfn.h b/include/linux/early_pfn.h
index 1b001c7..f9e40c3 100644
--- a/include/linux/early_pfn.h
+++ b/include/linux/early_pfn.h
@@ -3,31 +3,52 @@
 #ifndef __EARLY_PFN_H
 #define __EARLY_PFN_H
 #ifdef CONFIG_HAVE_MEMBLOCK_PFN_VALID
+static int early_region_idx __init_memblock = -1;
 ulong __init_memblock memblock_next_valid_pfn(ulong pfn)
 {
 	struct memblock_type *type = &memblock.memory;
-	unsigned int right = type->cnt;
-	unsigned int mid, left = 0;
+	struct memblock_region *regions = type->regions;
+	uint right = type->cnt;
+	uint mid, left = 0;
+	ulong start_pfn, end_pfn, next_start_pfn;
 	phys_addr_t addr = PFN_PHYS(++pfn);
 
+	/* fast path, return pfn+1 if next pfn is in the same region */
+	if (early_region_idx != -1) {
+		start_pfn = PFN_DOWN(regions[early_region_idx].base);
+		end_pfn = PFN_DOWN(regions[early_region_idx].base +
+				regions[early_region_idx].size);
+
+		if (pfn >= start_pfn && pfn < end_pfn)
+			return pfn;
+
+		early_region_idx++;
+		next_start_pfn = PFN_DOWN(regions[early_region_idx].base);
+
+		if (pfn >= end_pfn && pfn <= next_start_pfn)
+			return next_start_pfn;
+	}
+
+	/* slow path, do the binary searching */
 	do {
 		mid = (right + left) / 2;
 
-		if (addr < type->regions[mid].base)
+		if (addr < regions[mid].base)
 			right = mid;
-		else if (addr >= (type->regions[mid].base +
-				  type->regions[mid].size))
+		else if (addr >= (regions[mid].base + regions[mid].size))
 			left = mid + 1;
 		else {
-			/* addr is within the region, so pfn is valid */
+			early_region_idx = mid;
 			return pfn;
 		}
 	} while (left < right);
 
 	if (right == type->cnt)
 		return -1UL;
-	else
-		return PHYS_PFN(type->regions[right].base);
+
+	early_region_idx = right;
+
+	return PHYS_PFN(regions[early_region_idx].base);
 }
 EXPORT_SYMBOL(memblock_next_valid_pfn);
 #endif /*CONFIG_HAVE_MEMBLOCK_PFN_VALID*/
-- 
2.7.4

  parent reply	other threads:[~2018-04-11  7:23 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-11  7:21 [PATCH v8 0/6] optimize memblock_next_valid_pfn and early_pfn_valid on arm and arm64 Jia He
2018-04-11  7:21 ` [PATCH v8 1/6] arm: arm64: introduce CONFIG_HAVE_MEMBLOCK_PFN_VALID Jia He
2018-04-11  7:21 ` [PATCH v8 2/6] mm: page_alloc: remain memblock_next_valid_pfn() on arm/arm64 Jia He
2018-04-11  7:21 ` Jia He [this message]
2018-04-11  7:21 ` [PATCH v8 4/6] mm/memblock: introduce memblock_search_pfn_regions() Jia He
2018-04-11  7:21 ` [PATCH v8 5/6] arm: arm64: introduce pfn_valid_region() Jia He
2018-04-11  7:21 ` [PATCH v8 6/6] mm: page_alloc: reduce unnecessary binary search in early_pfn_valid() Jia He
2018-05-04  2:45 ` [PATCH v8 0/6] optimize memblock_next_valid_pfn and early_pfn_valid on arm and arm64 Jia He
2018-05-04 16:08   ` Daniel Vacek
2018-05-04 16:53     ` Pavel Tatashin
2018-05-04 18:33       ` Daniel Vacek
2018-05-07  1:10       ` Jia He

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