Date: Sun, 02 Sep 2007 11:56:27 +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: <46DA96DB.2090700@cran.org.uk> In-Reply-To: <20070902095417.GN1181@turion.vk2pj.dyndns.org> References: <46D83351.9000407@cran.org.uk> <46D8719A.1070109@cran.org.uk> <20070901204947.GY1181@turion.vk2pj.dyndns.org> <46D9EE1E.9030009@cran.org.uk> <20070902095417.GN1181@turion.vk2pj.dyndns.org>
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Peter Jeremy wrote: > On 2007-Sep-01 23:56:30 +0100, Bruce Cran <bruce@cran.org.uk> wrote: > >> 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. >> > > Half the clock rate implies twice the interrupt load - it it should be > about 3.5% at 531MHz if its 7% at 265MHz. If you're seeing something > significantly different then there is some other factor at work. > > It seems there is something different happening, but I don't know if it's to do with FreeBSD or just the way the CPU works. At 531MHz the "swi4: clock sio" task uses 0.2% CPU and the "interrupt" line in top goes up to about 1.6%. At 265MHz the "swi4: clock sio" task uses about 10% CPU and the "interrupt" line varies between 14 and 20%. -- Bruce Cran
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