From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262386AbULOQp7 (ORCPT ); Wed, 15 Dec 2004 11:45:59 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262383AbULOQp7 (ORCPT ); Wed, 15 Dec 2004 11:45:59 -0500 Received: from out014pub.verizon.net ([206.46.170.46]:15241 "EHLO out014.verizon.net") by vger.kernel.org with ESMTP id S262386AbULOQok (ORCPT ); Wed, 15 Dec 2004 11:44:40 -0500 From: Gene Heskett Reply-To: gene.heskett@verizon.net Organization: Organization: None, detectable by casual observers To: linux-kernel@vger.kernel.org Subject: Re: USB making time drift [was Re: dynamic-hz] Date: Wed, 15 Dec 2004 11:44:38 -0500 User-Agent: KMail/1.7 Cc: Andrea Arcangeli , Pavel Machek , Zwane Mwaikambo , Con Kolivas References: <20041213002751.GP16322@dualathlon.random> <200412142159.23488.gene.heskett@verizon.net> <20041215091741.GA16322@dualathlon.random> In-Reply-To: <20041215091741.GA16322@dualathlon.random> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200412151144.38785.gene.heskett@verizon.net> X-Authentication-Info: Submitted using SMTP AUTH at out014.verizon.net from [151.205.42.94] at Wed, 15 Dec 2004 10:44:39 -0600 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wednesday 15 December 2004 04:17, Andrea Arcangeli wrote: >On Tue, Dec 14, 2004 at 09:59:23PM -0500, Gene Heskett wrote: >> Which way? I was running quite fast here, several minutes an > >In the future, if I disable the logic it goes in the past at the > same speed it was previously going in the future. > >> hour, then I discovered the tickadj command, found its default >> was 10000, and started reducing it. At 9926, I'm staying within >> a sec an hour now. I have no idea when this started, I didn't > >That seems quite an hack, note I did an hack too and it make the > drift much smaller (it gets manageable). But our modifications are > wrong. > >The point is that this didn't happen with HZ=100, so it's not that >tickadj is wrong, it's the tick adjustment code that doesn't work. > The HZ=1000 is the culprit? >You may want to recompile your kernel with HZ=100 and verify it goes >away (I didn't verify myself, but I verified the max irq latency I > get is 4msec, and in turn I'm sure HZ=100 would fix it Humm, that might also reduce the obviousness of the irq activity in the audio, there are times when I can hear it very plainly while a low level audio src is in use, like the sub-millivolt levels that come out of my Hauppauge WinTV-GO+FM card. I keep having to turn the master down to almost zip in order to keep it from sounding like I have mice chewing in the walls, but its coming from the speakers. Onboard AC-97 audio of course. Crappy stuff... Humm, 100HZ would translate to 10 millisecond intervals. If you had a 4 millisecond latency, that would be spread over 4 of the 1000 hz interrupts. That sounds rather confusing to the service routine I imagine. I'll do that just for grins & report back. -- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) 99.30% setiathome rank, not too shabby for a WV hillbilly Yahoo.com attorneys please note, additions to this message by Gene Heskett are: Copyright 2004 by Maurice Eugene Heskett, all rights reserved.