Date: Sat, 01 Sep 2007 23:56:30 +0100 From: Bruce Cran <bruce@cran.org.uk> To: Peter Jeremy <peterjeremy@optushome.com.au> Cc: current@freebsd.org Subject: Re: High interrupt load on VIA C3 machine Message-ID: <46D9EE1E.9030009@cran.org.uk> In-Reply-To: <20070901204947.GY1181@turion.vk2pj.dyndns.org> References: <46D83351.9000407@cran.org.uk> <46D8719A.1070109@cran.org.uk> <20070901204947.GY1181@turion.vk2pj.dyndns.org>
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Peter Jeremy wrote: > On 2007-Aug-31 20:52:58 +0100, Bruce Cran <bruce@cran.org.uk> 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
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