Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757754AbZAHRXs (ORCPT ); Thu, 8 Jan 2009 12:23:48 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751527AbZAHRXh (ORCPT ); Thu, 8 Jan 2009 12:23:37 -0500 Received: from casper.infradead.org ([85.118.1.10]:37115 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751206AbZAHRXf (ORCPT ); Thu, 8 Jan 2009 12:23:35 -0500 Subject: Re: [PATCH -v7][RFC]: mutex: implement adaptive spinning From: Peter Zijlstra To: Linus Torvalds Cc: Ingo Molnar , Steven Rostedt , paulmck@linux.vnet.ibm.com, Gregory Haskins , Matthew Wilcox , Andi Kleen , Chris Mason , Andrew Morton , Linux Kernel Mailing List , linux-fsdevel , linux-btrfs , Thomas Gleixner , Nick Piggin , Peter Morreale , Sven Dietrich In-Reply-To: References: <1231347442.11687.344.camel@twins> <1231365115.11687.361.camel@twins> <1231366716.11687.377.camel@twins> <1231408718.11687.400.camel@twins> <20090108141808.GC11629@elte.hu> <1231426014.11687.456.camel@twins> Content-Type: text/plain Content-Transfer-Encoding: 7bit Date: Thu, 08 Jan 2009 18:23:12 +0100 Message-Id: <1231435392.11687.520.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.24.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1266 Lines: 35 On Thu, 2009-01-08 at 08:58 -0800, Linus Torvalds wrote: > > Ok, I've gone through -v7, and I'm sure you're all shocked to hear it, but > I have no complaints. *cheer*, except I guess we need to figure out what goes bad for Chris. > Except that you dropped all the good commit > commentary you had earlier ;) Yeah, I've yet to add that back, will do. > The patch looks pretty good (except for the big "#if 0" block in > mutex-debug.c that I hope gets fixed, but I can't even really claim that I > can be bothered), the locking looks fine (ie no locking at all), and the > numbers seem pretty convinving. > > Oh, and I think the open-coded > > atomic_cmpxchg(count, 1, 0) == 1 > > could possibly just be replaced with a simple __mutex_fastpath_trylock(). > I dunno. __mutex_fastpath_trylock() isn't always that neat -- see include/asm-generic/mutex-xchg.h -- and its a NOP on DEBUG_MUTEXES. Note how I used old_val for the list_empty() thing as well, we could possibly drop that extra condition though. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/