From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Mon, 19 Mar 2001 23:23:47 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Mon, 19 Mar 2001 23:23:37 -0500 Received: from mpdr0.chicago.il.ameritech.net ([206.141.239.142]:35472 "EHLO mailhost.chi.ameritech.net") by vger.kernel.org with ESMTP id ; Mon, 19 Mar 2001 23:23:27 -0500 Message-ID: <3AB6DAFB.1E8F14DB@ameritech.net> Date: Mon, 19 Mar 2001 22:22:19 -0600 From: watermodem X-Mailer: Mozilla 4.76 [en] (X11; U; Linux 2.4.2 i686) X-Accept-Language: en MIME-Version: 1.0 To: Matti Aarnio CC: "linux-kernel@vger.kernel.org" Subject: Re: Jiffy question and sound. In-Reply-To: <3AB5A53F.F8B0373B@ameritech.net> <20010319114615.E23336@mea-ext.zmailer.org> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Matti Aarnio wrote: > > On Mon, Mar 19, 2001 at 12:20:47AM -0600, watermodem wrote: > > With the 2.4.0 kernel the loops_per_sec field was replaced (for i386) > > with current_cpu_data.loops_per_jiffy. > ... > > #define LOOPS_PER_SEC current_cpu_data.loops_per_jiffy * 100 > > The intention was to accomodate systems with faster than 2 GHz clock > at which the LOOPS_PER_SEC counter spins around a bit too fast.. > ('signed long' at i386 handles 0..2G just fine, then it thinks the sign > got inverted.. 'unsigned long' works fine until 4 GHz processors.) > My sound card uses ALSA and ALSA wasn't available yet for the new kernel. So.. Noting that LOOPS_PER_SEC was what failed in the kernel I modified it and compiled. I am not associated in anyway with the ALSA folks just wanted too listen to music while working away. I have no idea why it needs it or if it is busy-looping... (I hope not). > Why does the ALSA need LOOPS_PER_SEC ? > Is it doing timing by busy-looping ? > > > Now compiling the same ALSA modules with 2.4.2 this problem happens > > much quicker and you don't need any other activity. In fact it is hard > > to play more than half a song. (MP3) > > It doesn't matter if what set of music players or tools I use the > > problem is quite visible. > > > > When I boot back to the original 2.2.x kernel everything is perfect. > > > > So I guess I have a few questions here. > > 1) Is a jiffy 100th of a second or is it smaller (so my loop count > > is starving things.) (10ms) ? > > "HZ" is the answer. E.g. Alpha has HZ=1024, while i386 has HZ=100 > Nearly all architectures have different values based on what some > other UNIX uses at given system. > > > 2) Why is it so much worse in 2.4.2 than 2.4.0? > > 3) Any other "gotch's" that are important to watch for when moving > > 2.2.x drivers to 2.4.x? > > The FAQ may have some pointers to "porting drivers to 2.4" documents. > > > Thanks.... > > Watermodem > > - > > Please read the FAQ at http://www.tux.org/lkml/ > > /Matti Aarnio