From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261505AbVGLO6k (ORCPT ); Tue, 12 Jul 2005 10:58:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261491AbVGLO5B (ORCPT ); Tue, 12 Jul 2005 10:57:01 -0400 Received: from dvhart.com ([64.146.134.43]:17334 "EHLO localhost.localdomain") by vger.kernel.org with ESMTP id S261450AbVGLO4s (ORCPT ); Tue, 12 Jul 2005 10:56:48 -0400 Date: Tue, 12 Jul 2005 07:56:47 -0700 From: "Martin J. Bligh" Reply-To: "Martin J. Bligh" To: Lee Revell Cc: Chris Friesen , Diego Calleja , azarah@nosferatu.za.org, akpm@osdl.org, cw@f00f.org, linux-kernel@vger.kernel.org, torvalds@osdl.org, christoph@lameter.org Subject: Re: [PATCH] i386: Selectable Frequency of the Timer Interrupt Message-ID: <14170000.1121180207@[10.10.2.4]> In-Reply-To: <1121178300.2632.51.camel@mindpipe> References: <200506231828.j5NISlCe020350@hera.kernel.org> <20050708214908.GA31225@taniwha.stupidest.org> <20050708145953.0b2d8030.akpm@osdl.org> <1120928891.17184.10.camel@lycan.lan> <1120932991.6488.64.camel@mindpipe> <20050709203920.394e970d.diegocg@gmail.com> <1120934466.6488.77.camel@mindpipe> <176640000.1121107087@flay> <1121113532.2383.6.camel@mindpipe> <42D2D912.3090505@nortel.com> <1121128260.2632.12.camel@mindpipe> <165840000.1121141256@[10.10.2.4]> <1121141602.2632.31.camel@mindpipe> <188690000.1121142633@[10.10.2.4]> <1121178300.2632.51.camel@mindpipe> X-Mailer: Mulberry/2.2.1 (Linux/x86) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org --Lee Revell wrote (on Tuesday, July 12, 2005 10:24:59 -0400): > On Mon, 2005-07-11 at 21:30 -0700, Martin J. Bligh wrote: >> Exactly what problems >> *does* it cause (in visible effect, not "timers are less granular"). >> Jittery audio/video? How much worse is it? > > Yes, exactly. Say you need to deliver a frame of audio or video every > 5ms. Ummm. that's a 200HZ refresh rate, is it not? That seems unreasonable (to a lay-person, as far as video goes). > You have a rendering thread and a display thread that communicate > via FIFOs. The main thread waits in select() for the next frame to > complete rendering or for the deadline to expire. That's next to > impossible with HZ=100, because the best you can do is the deadline > +-10ms. With HZ=1000 it's no problem. So if we have a 50HZ refresh rate, and a HZ rate of 250 or 300, it'll work fine then, right? I know that's actually some error in the timers, so it may be 2 or 3 ticks, not 1, but if we're running HZ at 5 or 6 times the frequency of video, presumably that'd still work fine? M.