Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965141AbVLVJBv (ORCPT ); Thu, 22 Dec 2005 04:01:51 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965143AbVLVJBv (ORCPT ); Thu, 22 Dec 2005 04:01:51 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:31369 "EHLO mx3.mail.elte.hu") by vger.kernel.org with ESMTP id S965141AbVLVJBu (ORCPT ); Thu, 22 Dec 2005 04:01:50 -0500 Date: Thu, 22 Dec 2005 10:01:12 +0100 From: Ingo Molnar To: john stultz Cc: Roman Zippel , linux-kernel@vger.kernel.org, Thomas Gleixner Subject: Re: [PATCH/RFC 10/10] example of simple continuous gettimeofday Message-ID: <20051222090112.GA6377@elte.hu> References: <1135219395.5873.96.camel@leatherman> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1135219395.5873.96.camel@leatherman> User-Agent: Mutt/1.4.2.1i X-ELTE-SpamScore: 0.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=0.0 required=5.9 tests=AWL autolearn=no SpamAssassin version=3.0.3 0.0 AWL AWL: From: address is in the auto white-list X-ELTE-VirusStatus: clean Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1756 Lines: 37 * john stultz wrote: > > - I still don't like the idea of a generic gettimeofday() as it prevents > > more optimized versions, e.g. on the one end with a 1MHz clock you only > > have usec resolution anyway and this allows to keep almost everything > > within 32bits. On the other end 64bit archs can avoid the "if (nsec > > > NSEC_PER_SEC)" by doing something like ppc64 does, but requires a > > different scaling of the values (to sec instead of nsec). > > Fair enough. I agree arches should be able to have their own arch > specific implementations. If you really have to micro-optimize > everything, just don't enable CONFIG_GENERIC_TIME and have your own > timekeeping subsystem! > > But at the same time, I don't like the idea of needlessly having 26 > different versions of gettimeofday that do exactly the same thing > modulo a few bugs. :) I like the first 9 patches, but regarding 10/10 i very much agree with John: it moves us to per-arch gettimeofday again, which is a big step backwards and reverts some of the biggest advantage of John's clocksource patchset! Also, lets face it: with the union ktime_t type most of the '64-bit is slow on 32-bit' issues are much less of a problem. If some 32-bit arch wants to pull off its own timekeeping system, it can do so - but otherwise we want to move towards generic, unified (as far as it makes sense) and generally 64-bit-optimized subsystems. In 1995 i'd have agreed with Roman, but not in 2005. Ingo - 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/