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From:   Jia He <hejianet@gmail.com>
To:     Russell King <linux@armlinux.org.uk>,
        Catalin Marinas <catalin.marinas@arm.com>,
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Cc:     Wei Yang <richard.weiyang@gmail.com>,
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        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 v6 4/5] arm: arm64: introduce pfn_valid_region()
Date:   Tue,  3 Apr 2018 19:56:18 -0700
Message-Id: <1522810579-7466-5-git-send-email-hejianet@gmail.com>
In-Reply-To: <1522810579-7466-1-git-send-email-hejianet@gmail.com>
References: <1522810579-7466-1-git-send-email-hejianet@gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
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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 pfn++ is still in the same region. Thus
we can avoid do the slow binary searches.

Currently it only improve the performance on arm/arm64 and will have no
impact on other arches.

Signed-off-by: Jia He <jia.he@hxt-semitech.com>
---
 include/linux/arm96_common.h | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/include/linux/arm96_common.h b/include/linux/arm96_common.h
index 2f4dea4..bb86bd3 100644
--- a/include/linux/arm96_common.h
+++ b/include/linux/arm96_common.h
@@ -48,5 +48,29 @@ ulong __init_memblock memblock_next_valid_pfn(ulong pfn)
 	return PHYS_PFN(regions[early_region_idx].base);
 }
 EXPORT_SYMBOL(memblock_next_valid_pfn);
+
+int pfn_valid_region(ulong pfn)
+{
+	ulong start_pfn, end_pfn;
+	struct memblock_type *type = &memblock.memory;
+	struct memblock_region *regions = type->regions;
+
+	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 !memblock_is_nomap(
+					&regions[early_region_idx]);
+	}
+
+	early_region_idx = memblock_search_pfn_regions(pfn);
+	if (early_region_idx == -1)
+		return false;
+
+	return !memblock_is_nomap(&regions[early_region_idx]);
+}
+EXPORT_SYMBOL(pfn_valid_region);
 #endif /*CONFIG_HAVE_ARCH_PFN_VALID*/
 #endif /*__ARM96_COMMON_H*/
-- 
2.7.4