linux-kernel - Re: [GIT PULL] adaptive spinning mutexes

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Message-Id: <1231958447.8269.30.camel@think.oraclecorp.com>
Date:	Wed, 14 Jan 2009 13:40:46 -0500
From:	Chris Mason <chris.mason@...cle.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Gregory Haskins <ghaskins@...ell.com>,
	Matthew Wilcox <matthew@....cx>,
	Andi Kleen <andi@...stfloor.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	linux-btrfs <linux-btrfs@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Nick Piggin <npiggin@...e.de>,
	Peter Morreale <pmorreale@...ell.com>,
	Sven Dietrich <SDietrich@...ell.com>,
	Dmitry Adamushko <dmitry.adamushko@...il.com>,
	Johannes Weiner <hannes@...xchg.org>
Subject: Re: [GIT PULL] adaptive spinning mutexes

On Wed, 2009-01-14 at 19:33 +0100, Ingo Molnar wrote:
> * Peter Zijlstra <peterz@...radead.org> wrote:
> 
> > Full series, including changelogs available at:
> > 
> >  http://programming.kicks-ass.net/kernel-patches/mutex-adaptive-spin/
> > 
> > and should shortly appear in a git tree near Ingo :-)
> 
> Linus,
> 
> Please pull the adaptive-mutexes-for-linus git tree from:
> 
>    git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip.git adaptive-mutexes-for-linus
> 

I was going to put this into the btrfs tree, but since you have a branch
just for adaptive mutexes, is it easier to put there?

From: Chris Mason <chris.mason@...cle.com>

Btrfs: stop spinning on mutex_trylock and let the adaptive code spin for us

Mutexes now spin internally and the btrfs spin is no longer required for
performance.

Signed-off-by: Chris Mason <chris.mason@...cle.com>

diff --git a/fs/btrfs/locking.c b/fs/btrfs/locking.c
index 39bae77..40ba8e8 100644
--- a/fs/btrfs/locking.c
+++ b/fs/btrfs/locking.c
@@ -37,16 +37,6 @@
 
 int btrfs_tree_lock(struct extent_buffer *eb)
 {
-	int i;
-
-	if (mutex_trylock(&eb->mutex))
-		return 0;
-	for (i = 0; i < 512; i++) {
-		cpu_relax();
-		if (mutex_trylock(&eb->mutex))
-			return 0;
-	}
-	cpu_relax();
 	mutex_lock_nested(&eb->mutex, BTRFS_MAX_LEVEL - btrfs_header_level(eb));
 	return 0;
 }


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