From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932138AbVLMNJ4 (ORCPT ); Tue, 13 Dec 2005 08:09:56 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932120AbVLMNJ4 (ORCPT ); Tue, 13 Dec 2005 08:09:56 -0500 Received: from clock-tower.bc.nu ([81.2.110.250]:61094 "EHLO lxorguk.ukuu.org.uk") by vger.kernel.org with ESMTP id S932110AbVLMNJz (ORCPT ); Tue, 13 Dec 2005 08:09:55 -0500 Subject: Re: [PATCH 1/19] MUTEX: Introduce simple mutex implementation From: Alan Cox To: Oliver Neukum Cc: Ingo Molnar , David Howells , Nick Piggin , torvalds@osdl.org, akpm@osdl.org, hch@infradead.org, arjan@infradead.org, matthew@wil.cx, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org In-Reply-To: <200512131347.30464.oliver@neukum.org> References: <439E122E.3080902@yahoo.com.au> <20051213101300.GA2178@elte.hu> <20051213103420.GA6681@elte.hu> <200512131347.30464.oliver@neukum.org> Content-Type: text/plain Content-Transfer-Encoding: 7bit Date: Tue, 13 Dec 2005 13:09:31 +0000 Message-Id: <1134479371.11732.19.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 (2.2.3-2.fc4) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Maw, 2005-12-13 at 13:47 +0100, Oliver Neukum wrote: > > spinlock to do the cmpxchg. This means that there wont be one single > > global spinlock to emulate cmpxchg, but the mutex's own spinlock can be > > used for it. > > Can't you use the pointer as a hash input? Some platforms already do this for certain sets of operations like atomic_t. The downside however is that you no longer control the lock contention or cache line bouncing. It becomes a question of luck rather than science as to how well it scales.