Date: Mon, 7 Mar 2011 15:01:16 +0000 From: "b. f." <bf1783@googlemail.com> To: Martin Birgmeier <martin.birgmeier@aon.at> Cc: freebsd-hackers@FreeBSD.org Subject: Re: All CPUs always running at profhz Message-ID: <AANLkTin1qQQg0U_U7K0RpixduW4CeeGbtjS5fjY-T52p@mail.gmail.com>
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> I have systems running 7.4 and 8.2. The newer ones (in terms of age of > hardware) are always running at profhz, i.e., when executing a "systat > -vm 1" I see that all cores always get profhz interrupts per second. > > An older machine running 7.4 is running at hz (which for this machine I > set to kern.hz=200 in loader.conf). > > Using ps -o ...,flags,... I see that no process has profiling turned on. > > Why is this so? > > Especially on laptops, I'd like to save power by lowering the interrupt > rate. I have not analyzed this problem. However, by using 9-CURRENT, together with http://people.freebsd.org/~mav/tm6292_idle.patch , removing DEVICE_POLLING from my kernel, and reducing kern.hz to 100, I was able to achieve reported interrupt rates of ~35-40 Hz on my UP machines when idle, and substantial reductions when the machines were loaded, as well. When used with other power-saving measures, this was a big help. b.
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