From owner-freebsd-current@FreeBSD.ORG Sat Sep 1 22:57:54 2007 Return-Path: Delivered-To: current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 82B0116A419 for ; Sat, 1 Sep 2007 22:57:54 +0000 (UTC) (envelope-from bruce@cran.org.uk) Received: from muon.bluestop.org (muon.bluestop.org [80.68.94.188]) by mx1.freebsd.org (Postfix) with ESMTP id 4B6D213C45B for ; Sat, 1 Sep 2007 22:57:54 +0000 (UTC) (envelope-from bruce@cran.org.uk) Received: from muon.draftnet (dyn-62-56-105-44.dslaccess.co.uk [62.56.105.44]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by muon.bluestop.org (Postfix) with ESMTP id B70DE3000D; Sat, 1 Sep 2007 23:53:48 +0100 (BST) Message-ID: <46D9EE1E.9030009@cran.org.uk> Date: Sat, 01 Sep 2007 23:56:30 +0100 From: Bruce Cran User-Agent: Thunderbird 2.0.0.6 (X11/20070809) MIME-Version: 1.0 To: Peter Jeremy References: <46D83351.9000407@cran.org.uk> <46D8719A.1070109@cran.org.uk> <20070901204947.GY1181@turion.vk2pj.dyndns.org> In-Reply-To: <20070901204947.GY1181@turion.vk2pj.dyndns.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: current@freebsd.org Subject: Re: High interrupt load on VIA C3 machine X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 01 Sep 2007 22:57:54 -0000 Peter Jeremy wrote: > On 2007-Aug-31 20:52:58 +0100, Bruce Cran wrote: > >> This appears to be an issue with powerd/cpufreq - disabling powerd reduces >> the interrupt load to a couple of percent at most, and the clock interrupt >> task now only accumulates CPU time very slowly (previously it was using 7% >> CPU all the time). >> > > I'm not familiar with the VIA CPUs but how slowly can powerd make the > CPU run? The top extract you posted show the system was idle so its > likely that powerd had wound the clock to a minimum. The amount of > code executed by the interrupt handlers remains the same but will take > longer at slower clock speeds so the percenatage is higher. > > You can experiment for yourself by enabling only cpufreq and using > sysctl. dev.cpu.0.freq_levels lists all supported possible CPU rates > and you can change the clock frequency by assigning dev.cpu.0.freq. > The VIA C3 supports 2 frequencies - 531 and 265 MHz. The high interrupt load only occurs when I set dev.cpu.0.freq to 265, which makes sense. -- Bruce Cran