Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932173AbVJTQ6o (ORCPT ); Thu, 20 Oct 2005 12:58:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932484AbVJTQ6o (ORCPT ); Thu, 20 Oct 2005 12:58:44 -0400 Received: from ms-smtp-02.nyroc.rr.com ([24.24.2.56]:18875 "EHLO ms-smtp-02.nyroc.rr.com") by vger.kernel.org with ESMTP id S932173AbVJTQ6n (ORCPT ); Thu, 20 Oct 2005 12:58:43 -0400 Date: Thu, 20 Oct 2005 12:58:29 -0400 (EDT) From: Steven Rostedt X-X-Sender: rostedt@localhost.localdomain To: john stultz cc: Ingo Molnar , tglx@linutronix.de, linux-kernel@vger.kernel.org Subject: Re: Ktimer / -rt9 (+custom) monotonic_clock going backwards. In-Reply-To: <1129826750.27168.163.camel@cog.beaverton.ibm.com> Message-ID: 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> <1129826750.27168.163.camel@cog.beaverton.ibm.com> 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: 1302 Lines: 36 On Thu, 20 Oct 2005, 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. > > 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)? > Thomas showed me a trick with the ktimers API, that I use to schedule my custom scheduler. If you set periodic_hook to be called via ktimer with a prio of -1, it will force the timer to be run in the timer interrupt instead of a softirq task. Now the issue is the latency this would cause and to make sure that periodic_hook only grabs raw locks. Ingo? -- 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/