From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754247Ab0F3I4g (ORCPT ); Wed, 30 Jun 2010 04:56:36 -0400 Received: from casper.infradead.org ([85.118.1.10]:39845 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753850Ab0F3I4e convert rfc822-to-8bit (ORCPT ); Wed, 30 Jun 2010 04:56:34 -0400 Subject: Re: [PATCH 2/4, v2] x86: enlightenment for ticket spin locks - Xen implementation From: Peter Zijlstra To: Jan Beulich Cc: jeremy.fitzhardinge@citrix.com, mingo@elte.hu, tglx@linutronix.de, Ky Srinivasan , linux-kernel@vger.kernel.org, hpa@zytor.com In-Reply-To: <4C2B21D20200007800008BDF@vpn.id2.novell.com> References: <4C2A200F02000078000089E4@vpn.id2.novell.com> <1277885135.1868.72.camel@laptop> <4C2B21D20200007800008BDF@vpn.id2.novell.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Wed, 30 Jun 2010 10:56:20 +0200 Message-ID: <1277888180.1868.84.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2010-06-30 at 09:52 +0100, Jan Beulich wrote: > > why is that a rwlock?, those things are useless. > > Because potentially each CPU's lock gets acquired for reading during > unlock, while only the locking CPU's one needs to be acquired for > writing during lock. Can you say: scalability nightmare? but then its Xen code so who cares.. /me pretends he never saw it