Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Mon, 23 Jul 2001 17:15:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Mon, 23 Jul 2001 17:15:28 -0400 Received: from [47.129.117.131] ([47.129.117.131]:48512 "HELO pcard0ks.ca.nortel.com") by vger.kernel.org with SMTP id ; Mon, 23 Jul 2001 17:15:12 -0400 Message-ID: <3B5C93C9.8DF406CC@nortelnetworks.com> Date: Mon, 23 Jul 2001 17:14:49 -0400 From: Chris Friesen X-Mailer: Mozilla 4.77 [en] (X11; U; Linux 2.4.3-custom i686) X-Accept-Language: en MIME-Version: 1.0 To: Alan Cox Cc: "Friesen, Christopher [CAR:VS16:EXCH]" , Linus Torvalds , Andrea Arcangeli , Jeff Dike , user-mode-linux-user , linux-kernel , Jan Hubicka Subject: Re: user-mode port 0.44-2.4.7 In-Reply-To: Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Original-Recipient: rfc822;linux-kernel-outgoing Alan Cox wrote: > > > Suppose I loop against xtime reaching a particular value. While this is > > xtime isnt used this way that I can see. jiffies however is. There are good > arguments for getting rid of most [ab]use of jiffies however. For one its > pretty important to scaling on both big mainframes and beowulf setups doing > heavy computation to reduce timer ticks jiffies is (as of 2.4.7 anyways) marked as volatile, so we're safe there. My point is this--should someone writing badly designed (but technically correct) code be able to totally hose the system? The only difference between volatile and normal is that if it is marked as volatile it must be accessed every time rather than being pre-cached. If we never spin on accessing xtime, then the fact that we can't optimize it shouldn't hurt. (Am I wrong here? If I am then please explain because I'm missing something...) If someone ever *does* spin on xtime, then we really don't want to optimize that access out of the loop, because doing so could cause nasty problems. -- Chris Friesen | MailStop: 043/33/F10 Nortel Networks | work: (613) 765-0557 3500 Carling Avenue | fax: (613) 765-2986 Nepean, ON K2H 8E9 Canada | email: cfriesen@nortelnetworks.com - 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/