Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964878AbVJUGDY (ORCPT ); Fri, 21 Oct 2005 02:03:24 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964880AbVJUGDY (ORCPT ); Fri, 21 Oct 2005 02:03:24 -0400 Received: from ms-smtp-02.nyroc.rr.com ([24.24.2.56]:51190 "EHLO ms-smtp-02.nyroc.rr.com") by vger.kernel.org with ESMTP id S964878AbVJUGDX (ORCPT ); Fri, 21 Oct 2005 02:03:23 -0400 Date: Fri, 21 Oct 2005 02:03:13 -0400 (EDT) From: Steven Rostedt X-X-Sender: rostedt@localhost.localdomain To: Ingo Molnar cc: john stultz , tglx@linutronix.de, linux-kernel@vger.kernel.org Subject: Re: Ktimer / -rt9 (+custom) monotonic_clock going backwards. In-Reply-To: <20051020193214.GA21613@elte.hu> Message-ID: References: <20051020073416.GA28581@elte.hu> <20051020080107.GA31342@elte.hu> <20051020085955.GB2903@elte.hu> <1129826750.27168.163.camel@cog.beaverton.ibm.com> <20051020193214.GA21613@elte.hu> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1212 Lines: 39 On Thu, 20 Oct 2005, Ingo Molnar wrote: > > * john stultz wrote: > > > > > 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. > > no, this is really a bad optimization that causes unrobustness. > Correctness and robustness comes first. It is so easy to cause a > 500-1000msec delay in the kernel, due to a bad driver or anything. The > timekeeping code should not break like that. > FYI, With rc4-rt13 and changing cycle_t to u64, my machine ran all night without one backward step. Since it use to show up after a couple of hours, I would say that this is the fix. John, Do you want me to take a crack at changing the periodic_hook into using the ktimer code? I understand Ingo's kernel much more than you, but you definitely understand the timing code better than I. Cheers, -- Steve - 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/