linux-kernel - Re: Shrink the held_lock struct by using bitfields.

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Message-ID: <20070102233824.GF18033@redhat.com>
Date:	Tue, 2 Jan 2007 18:38:24 -0500
From:	Dave Jones <davej@...hat.com>
To:	mingo@...hat.com, Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: Shrink the held_lock struct by using bitfields.

On Tue, Jan 02, 2007 at 06:35:58PM -0500, Dave Jones wrote:

Sent the wrong diff.  Here's the fixed version...

Shrink the held_lock struct by using bitfields.
This shrinks task_struct on lockdep enabled kernels by 480 bytes.

Signed-off-by: Dave Jones <davej@...hat.com>

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index ea097dd..ba81cce 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -175,11 +175,11 @@ struct held_lock {
 	 * The following field is used to detect when we cross into an
 	 * interrupt context:
 	 */
-	int				irq_context;
-	int				trylock;
-	int				read;
-	int				check;
-	int				hardirqs_off;
+	unsigned char irq_context:1;
+	unsigned char trylock:1;
+	unsigned char read:2;
+	unsigned char check:1;
+	unsigned char hardirqs_off:1;
 };

 /*

-- 
http://www.codemonkey.org.uk
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