Date: Thu, 17 Jan 2008 09:03:49 -0800 From: Nate Lawson <nate@root.org> To: =?UTF-8?B?RGFnLUVybGluZyBTbcO4cmdyYXY=?= <des@des.no> Cc: freebsd-current@freebsd.org, Maxim Sobolev <sobomax@digifonica.com>, Igor Mozolevsky <igor@hybrid-lab.co.uk>, Stefan Lambrev <stefan.lambrev@moneybookers.com> Subject: Re: powerd adaptive mode latching Message-ID: <478F8A75.5010701@root.org> In-Reply-To: <86myr4n4gp.fsf@ds4.des.no> References: <a2b6592c0801110351l382959ffh1d55f2bcd2e6ca1b@mail.gmail.com> <a2b6592c0801111119r148d3697hf75a59b7bf74d540@mail.gmail.com> <478930D2.90806@digifonica.com> <200801171115.43663.doconnor@gsoft.com.au> <86myr4n4gp.fsf@ds4.des.no>
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Dag-Erling Smørgrav wrote: > "Daniel O'Connor" <doconnor@gsoft.com.au> writes: >> One problem with it is that it lags behind actual usage by a few >> seconds (presumably averaging it). > > It is based on the (didle/dt) / (dtotal/dt) fraction computed from > kern.cp_time, which can take a while to ramp up. This is not easily > seen in a cursory reading of the code, as the fraction is computed in a > very roundabout way. While providing more accurate information to powerd is a good goal, I want to preempt any requests to move the scheduling algorithm into the kernel. Until we're making multiple changes a second by necessity, there's no reason to have the scheduler there. Note that inefficiencies in the current scheduling algorithm (2x up, 1x down) are not a cause to make decisions more quickly. The path should be first fix the algorithm by profiling replacements, then improve the liveness of data provided to it. >> Turning the LCD off saves about 4W too. > > Hmm, it would be interesting to experiment with varying backlight > brightness based on system load :) I think xscreensaver could do some of this based on interactivity. It already can blank the screen with dpms. Macbooks slowly dim before blanking. I often have a bg job that uses a lot of cpu (buildkernel?) so using cpu load wouldn't be good. -- Nate
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