From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [PATCH -v8][RFC] mutex: implement adaptive spinning Date: Mon, 12 Jan 2009 18:16:21 +0100 Message-ID: <1231780581.4371.193.camel@laptop> References: <1231774622.4371.96.camel@laptop> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: Ingo Molnar , "Paul E. McKenney" , 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 , Dmitry Adamushko To: Linus Torvalds Return-path: Received: from bombadil.infradead.org ([18.85.46.34]:44318 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750918AbZALRQp (ORCPT ); Mon, 12 Jan 2009 12:16:45 -0500 In-Reply-To: Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Mon, 2009-01-12 at 08:20 -0800, Linus Torvalds wrote: > > On Mon, 12 Jan 2009, Linus Torvalds wrote: > > > > You made it back into the locked version. > > Btw, even if you probably had some reason for this, one thing to note is > that I think Chris' performance testing showed that the version using a > lock was inferior to his local btrfs hack, while the unlocked version > actually beat his hack. > > Maybe I misunderstood his numbers, though. But if I followed that sub-part > of the test right, it really means that the locked version is pointless - > it will never be able to replace peoples local hacks for this same thing, > because it just doesn't give the performance people are looking for. > > Since the whole (and _only_) point of this thing is to perform well, > that's a big deal. Like said in reply to Chris' email, I just wanted to see if fairness was worth the effort, because the pure unlocked spin showed significant unfairness (and I know some people really care about some level of fairness). Initial testing with the simple test-mutex thing didn't show too bad numbers.