Date: Mon, 2 Jul 2007 00:16:04 +1000 (EST) From: Ian Smith <smithi@nimnet.asn.au> To: cpghost <cpghost@cordula.ws> Cc: freebsd-questions@freebsd.org Subject: Re: kern.hz="100" stops high-pitched whine Message-ID: <Pine.BSF.3.96.1070701234407.12944G-100000@gaia.nimnet.asn.au> In-Reply-To: <20070701120022.DCC6C16A4A5@hub.freebsd.org>
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On Sun, 01 Jul 2007 13:12:28 +0200 cpghost <cpghost@cordula.ws> wrote: > I'm using fan-less Soekris (266 MHz) and EPIA (500 MHz) > boards with -STABLE. Those boards have been emitting a > very high pitched annoying whine, similar to a dog > whistle. Not everyone I asked could hear it, but I was, > and it was driving me crazy for months. > > This whine stopped entirely the moment I put > kern.hz="100" in /boot/loader.conf and rebooted. > Quite relieving! Possibly a beat frequency between the 1kHz default slicing and some faster oscillator on board? You could play around with kern.clockrate, sometimes quite small frequency changes make a difference, especially if it's a harmonic. Default HZ jumped from 100 to 1000 probably around the time when more servers were seen running at nearer 3000MHz than 300 :) > Are there any reasons NOT changing kern.hz from the > default 1000 back to 100? With my typical mix of > desktop apps (EPIA) and networking / server (Soekris), > everything seems to be running just as smoothly with > 100 Hz than with 1000 Hz (testing now for two weeks > without problems). Even playing videos with mplayer > on the EPIA doesn't look different in any way. No problem then, and a lighter interrupt load; probably enough to notice in top. If you want to run dummynet or something else? wanting quicker ticking you could try HZ=200 - 500. 200Hz on my Celeron 300 works well. > Is it okay to stay with 100 Hz with this type of > low-speed CPU/boards? Or are there some compelling > reasons not to? If it's happy, smooth and keeping up, it's fine. Cheers, Ian
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