Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932474AbVJTQqF (ORCPT ); Thu, 20 Oct 2005 12:46:05 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932477AbVJTQqF (ORCPT ); Thu, 20 Oct 2005 12:46:05 -0400 Received: from e34.co.us.ibm.com ([32.97.110.152]:48352 "EHLO e34.co.us.ibm.com") by vger.kernel.org with ESMTP id S932474AbVJTQqC (ORCPT ); Thu, 20 Oct 2005 12:46:02 -0400 Subject: Re: Ktimer / -rt9 (+custom) monotonic_clock going backwards. From: john stultz To: Steven Rostedt Cc: Ingo Molnar , tglx@linutronix.de, linux-kernel@vger.kernel.org In-Reply-To: References: <1129734626.19559.275.camel@tglx.tec.linutronix.de> <1129747172.27168.149.camel@cog.beaverton.ibm.com> <20051020073416.GA28581@elte.hu> <20051020080107.GA31342@elte.hu> <20051020085955.GB2903@elte.hu> Content-Type: text/plain Date: Thu, 20 Oct 2005 09:45:50 -0700 Message-Id: <1129826750.27168.163.camel@cog.beaverton.ibm.com> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 (2.2.3-2.fc4) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1264 Lines: 43 On Thu, 2005-10-20 at 06:05 -0400, Steven Rostedt wrote: > > On Thu, 20 Oct 2005, Steven Rostedt wrote: > > > > > > > Not anymore. > > > > > > include/linux/time.h: > > > > > > /* timeofday base types */ > > > typedef s64 nsec_t; > > > typedef unsigned long cycle_t; > > > > > > > FYI, > > > > I just switched cycle_t to u64 and hackbench no longer makes the time go > > backwards. > > > > John, would this cause any problems to keep cycle_t at s64? > > I mean at u64. Performance would be the only concern. It had been a u64 before I started optimizing the code a bit. The real problem however was the timeofday_perioidic_hook() was being starved. Since not all clocksources are 64 bits wide (although most do not overflow as fast as 32bits of the TSC) I'm not sure that will always solve the issue. Ingo: Should the periodic_hook() call be converted to using the ktimer or some other interface to ensure that it will be regularly run at some frequency (currently 50ms, but that can be changed)? thanks -john - 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/