From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262128AbTJNKWM (ORCPT ); Tue, 14 Oct 2003 06:22:12 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262282AbTJNKWM (ORCPT ); Tue, 14 Oct 2003 06:22:12 -0400 Received: from dyn-ctb-210-9-243-42.webone.com.au ([210.9.243.42]:46596 "EHLO chimp.local.net") by vger.kernel.org with ESMTP id S262128AbTJNKWH (ORCPT ); Tue, 14 Oct 2003 06:22:07 -0400 Message-ID: <3F8BCAB3.2070609@cyberone.com.au> Date: Tue, 14 Oct 2003 20:06:43 +1000 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.4) Gecko/20030827 Debian/1.4-3 X-Accept-Language: en MIME-Version: 1.0 To: Jamie Lokier CC: Piet Delaney , George Anzinger , Clayton Weaver , linux-kernel@vger.kernel.org Subject: Re: Circular Convolution scheduler References: <20031006161733.24441.qmail@email.com> <3F833C06.7000802@mvista.com> <1066120643.25020.121.camel@www.piet.net> <20031014094655.GC24812@mail.shareable.org> In-Reply-To: <20031014094655.GC24812@mail.shareable.org> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Jamie Lokier wrote: >Piet Delaney wrote: > >>circular convolution is used with the Fast Fourier Transform. >>The frequency data goes from -N/2 ...0 ,,,, +N/2, >>multiplying in the frequency domain is the same as >>convolving in the time or space domain. The result of multiplying >>a time series by say a filter is the same as convolving it >>with the FFT of the filter. Both domains wrap around with the >>FFT, so the normal convolution associated with the Fourier >>transform is replace with the circular convolution. >> >>Many prediction algorithms are based on digital signal processing. >>The Kalman filter for example was used by Harvey for forecasting >>financial markets. The kernel likely has lots of time series that >>could be used for system identification for predicting how to best >>use system resources. >> > >Ok, but what is "circular convolution scheduling"? > > I don't know anything about it, but I don't see what exactly you'd be trying to predict: the kernel's scheduler _dictates_ scheduling behaviour, obviously. Also, "best use of system resources" wrt scheduling is a big ask considering there isn't one ideal scheduling pattern for all but the most trivial loads, even on a single processor computer (fairness, latency, priority, thoughput, etc). Its difficult to even say one pattern is better than another.