Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Wed, 31 Oct 2001 15:53:40 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Wed, 31 Oct 2001 15:53:31 -0500 Received: from [63.231.122.81] ([63.231.122.81]:2416 "EHLO lynx.adilger.int") by vger.kernel.org with ESMTP id ; Wed, 31 Oct 2001 15:53:18 -0500 Date: Wed, 31 Oct 2001 13:52:15 -0700 From: Andreas Dilger To: Gerhard Mack Cc: "Richard B. Johnson" , Tim Schmielau , vda , linux-kernel@vger.kernel.org Subject: Re: [Patch] Re: Nasty suprise with uptime Message-ID: <20011031135215.O16554@lynx.no> Mail-Followup-To: Gerhard Mack , "Richard B. Johnson" , Tim Schmielau , vda , linux-kernel@vger.kernel.org In-Reply-To:

Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.4i In-Reply-To: ; from gmack@innerfire.net on Wed, Oct 31, 2001 at 12:11:18PM -0800 X-GPG-Key: 1024D/0D35BED6 X-GPG-Fingerprint: 7A37 5D79 BF1B CECA D44F 8A29 A488 39F5 0D35 BED6 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Oct 31, 2001 12:11 -0800, Gerhard Mack wrote: > Yes that I understand and it works right up until the jiffie count wraps. > But now we have people adding cost to everything else just so we can all > have good uptime values. Since AFIK the drivers handle the wrap cleanly > the only thing that it bothers is the uptime stats. > > Now we have people making jiffies more expensive just to deal with uptime. > At least as far as I can see it should just be easier/better to make > uptime use something else. What about the following. Since jiffies wraps are extremely rare, it should be enough to have something along the lines of the following in the uptime code only (or globally accessible for any code that needs to use a full 64-bit jiffies value): u64 get_jiffies64(void) { static unsigned long jiffies_hi = 0; static unsigned long jiffies_last = INITIAL_JIFFIES; /* probably need locking for this part */ if (jiffies < jiffies_last) { /* We have a wrap */ jiffies_hi++; jiffies_last = jiffies; } return (jiffies | ((u64)jiffies_hi) << LONG_SHIFT)); } This means you need to call something that _checks_ the uptime (or needs the 64-bit jiffies value) at least once every 1.3 years. If you don't do it at least that often, you probably don't care about the uptime anyways. This only impacts anything that really needs a 64-bit jiffies count, and has zero impact everywhere else. Cheers, Andreas -- Andreas Dilger http://sourceforge.net/projects/ext2resize/ http://www-mddsp.enel.ucalgary.ca/People/adilger/ - 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/