From owner-freebsd-current Thu Sep 25 00:50:11 1997 Return-Path: Received: (from root@localhost) by hub.freebsd.org (8.8.7/8.8.7) id AAA03508 for current-outgoing; Thu, 25 Sep 1997 00:50:11 -0700 (PDT) Received: from usr03.primenet.com (tlambert@usr03.primenet.com [206.165.6.203]) by hub.freebsd.org (8.8.7/8.8.7) with ESMTP id AAA03494 for ; Thu, 25 Sep 1997 00:50:05 -0700 (PDT) Received: (from tlambert@localhost) by usr03.primenet.com (8.8.5/8.8.5) id AAA10623; Thu, 25 Sep 1997 00:49:54 -0700 (MST) From: Terry Lambert Message-Id: <199709250749.AAA10623@usr03.primenet.com> Subject: Re: timeout management (was: Re: cvs commit: ...) To: gibbs@plutotech.com (Justin T. Gibbs) Date: Thu, 25 Sep 1997 07:49:54 +0000 (GMT) Cc: finnag@guardian.no, gibbs@plutotech.com, archie@whistle.com, current@FreeBSD.ORG In-Reply-To: <199709250554.XAA20672@pluto.plutotech.com> from "Justin T. Gibbs" at Sep 24, 97 11:54:02 pm X-Mailer: ELM [version 2.4 PL23] Content-Type: text Sender: owner-freebsd-current@FreeBSD.ORG X-Loop: FreeBSD.org Precedence: bulk > >There was a lot of discussion on the kernel list about cascace_timers > >enabling timers now and then, in practice cascade_timers never move many > >timers so it's not really a problem, even less of a problem when it just > >grabs the timer lock. > > > >- Finn Arne > > If the granularity of the timer interval is large when compared to > the speed with which a given application generates timers for the same > interval, you could have a problem. > > If you want to do RT, I think you have to enable timers periodically, > or you may miss a deadline. It's worse than that. If the timer fires, and the timer was scheduled by a process with a higher RT priority than the current process, you have to involuntary context switch the current process. Running a floppy tape drive is probably at the highest RT priority you can manage, actually, in order to ensure coorect operation with a kernel based driver. Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers.