Date: Tue, 22 Jan 2008 07:39:25 +0000 From: "Christian Walther" <cptsalek@gmail.com> To: "Erich Dollansky" <oceanare@pacific.net.sg> Cc: Andreas Davour <ante@update.uu.se>, Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl>, freebsd-questions@freebsd.org Subject: Re: Throttle the CPU when the system is idle Message-ID: <14989d6e0801212339s657c0011w5a498ce538ba60d5@mail.gmail.com> In-Reply-To: <4794BB91.7070106@pacific.net.sg> References: <Pine.LNX.4.64.0801210437470.8344@Psilocybe.Update.UU.SE> <20080121094451.N1777@wojtek.tensor.gdynia.pl> <Pine.LNX.4.64.0801211612070.13228@Psilocybe.Update.UU.SE> <4794BB91.7070106@pacific.net.sg>
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On 21/01/2008, Erich Dollansky <oceanare@pacific.net.sg> wrote: > Hi, > > Andreas Davour wrote: > > On Mon, 21 Jan 2008, Wojciech Puchar wrote: > > > >>> > >>> I have toyed a bit with the dev.cpu.0.freq sysctl setting, and tried > >>> to lower it automatically when the system load goes down. For some > >>> reason it don't seem to work, even though the script works for simple > >>> debug output. > >>> > >>> Anyone have tried to do something similar? > >> > >> no but anyway - freebsd halts CPU when unused, even at full frequency > >> it uses very little power wne unused. > > > > Really? Good to know. I was wondering if I could make this laptop of > > mine a bit cooler, but then I guess not. > > I also believe that the CPU is actually halted when idle but using > powerd brings the temperatures on my machine still down. As powerd can > be adjusted in which interval it adjusts the CPU frequency, short tasks > run actually at the minimum frequency if the CPU was idle. [...] Roughly speaking the CPU is halted, but the duration of this sleep state depends on the speed the CPU is working at. Since the CPU has to wake up regularly to see if there are things to be done it does so more often at 2000MHz than at 200MHz, for example. Of course the sleep time is longer at 200MHz, which makes a system to appear sluggish. But on the other hand power savings are at max. Christian
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