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

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Date:	Fri, 16 Jan 2009 15:07:34 +0100
From:	Folkert van Heusden <folkert@...heusden.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...e.hu>, Matthew Wilcox <matthew@....cx>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Gregory Haskins <ghaskins@...ell.com>,
	Andi Kleen <andi@...stfloor.org>,
	Chris Mason <chris.mason@...cle.com>,
	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

> So I don't dispute at all that "mutex with spinning" performs better than 
> a mutex, but I _do_ claim that it has some potentially huge downsides 
> compared to a real spinlock. It may perform as well as a spinlock in the 
> nice common case, but then when you hit the non-common case you see the 
> difference between well-written code and badly written code.

Make it mount-point dependant. Then your mail-spool can use the spinlock
version and e.g. the /usr filesystem uses regular mutexes. Might be
tricky to implement I guess.


Folkert van Heusden

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