linux-kernel - [PATCH] module: Use binary search in lookup

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Date:	Wed, 18 May 2011 22:35:59 +0200
From:	Alessio Igor Bogani <abogani@...nel.org>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	Greg KH <greg@...ah.com>, Anders Kaseorg <andersk@...lice.com>,
	Tim Abbott <tabbott@...lice.com>,
	Tim Bird <tim.bird@...sony.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux Embedded <linux-embedded@...r.kernel.org>,
	Jason Wessel <jason.wessel@...driver.com>,
	Dirk Behme <dirk.behme@...glemail.com>,
	Christoph Hellwig <hch@...radead.org>,
	Alessio Igor Bogani <abogani@...nel.org>
Subject: [PATCH] module: Use binary search in lookup_symbol()

The function is_exported() with its helper function lookup_symbol() are used to
verify if a provided symbol is effectively exported by the kernel or by the
modules. Now that both have their symbols sorted we can replace a linear search
with a binary search which provide a considerably speed-up.

This work was supported by a hardware donation from the CE Linux Forum.

Signed-off-by: Alessio Igor Bogani <abogani@...nel.org>
Acked-by: Greg Kroah-Hartman <gregkh@...e.de>
---
 kernel/module.c |    7 ++-----
 1 files changed, 2 insertions(+), 5 deletions(-)

diff --git a/kernel/module.c b/kernel/module.c
index 1e2b657..795bdc7 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2055,11 +2055,8 @@ static const struct kernel_symbol *lookup_symbol(const char *name,
 	const struct kernel_symbol *start,
 	const struct kernel_symbol *stop)
 {
-	const struct kernel_symbol *ks = start;
-	for (; ks < stop; ks++)
-		if (strcmp(ks->name, name) == 0)
-			return ks;
-	return NULL;
+	return bsearch(name, start, stop - start,
+			sizeof(struct kernel_symbol), cmp_name);
 }
 
 static int is_exported(const char *name, unsigned long value,
-- 
1.7.4.1

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