Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965767AbXBOKRi (ORCPT ); Thu, 15 Feb 2007 05:17:38 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965769AbXBOKRi (ORCPT ); Thu, 15 Feb 2007 05:17:38 -0500 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:45051 "EHLO amd.ucw.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S965767AbXBOKRh (ORCPT ); Thu, 15 Feb 2007 05:17:37 -0500 Date: Thu, 15 Feb 2007 11:17:13 +0100 From: Pavel Machek To: Zachary Amsden Cc: Alan , Rusty Russell , Andi Kleen , Linux Kernel Mailing List , Andrew Morton , Jeremy Fitzhardinge , Chris Wright Subject: Re: [PATCH 9/11] Panic delay fix Message-ID: <20070215101713.GK26240@elf.ucw.cz> References: <200702060353.l163rUmj000771@zach-dev.vmware.com> <20070206122729.GC47229@muc.de> <45C8FA2D.6010706@vmware.com> <20070207123552.GD4481@ucw.cz> <1170880572.11736.4.camel@localhost.localdomain> <20070214125216.2befda78@localhost.localdomain> <45D36B49.5090109@vmware.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <45D36B49.5090109@vmware.com> X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.11+cvs20060126 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1115 Lines: 29 Hi! > >>We'd have to audit and figure out what udelays are for hardware and > >>which are not, but the evidence is that the vast majority of them are > >>for hardware and not needed for virtualization. > >> > > > >Which is irrelevant since the hardware drivers won't be used in a > >virtualised environment with any kind of performance optimisation. > > > > Which is why an audit is irrelevant for the most part. Note on the > performance below. You know it is ugly. Alan demonstrated it even hurts performance, but being ugly is the main problem. If you _need_ to avoid udelay() in some cases, introduce udelay_unless_virtualized(), and switch few users to it. Just globaly defining udelay to nop is _ugly_. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html - 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/