Date: Mon, 11 Apr 2005 12:36:51 +0200 From: Bruno Ducrot <ducrot@poupinou.org> To: Nate Lawson <nate@root.org> Cc: acpi@freebsd.org Subject: Re: Further testing of power management Message-ID: <20050411103651.GO2298@poupinou.org> In-Reply-To: <4259945C.4020904@root.org> References: <20050408215912.E65115D07@ptavv.es.net> <4259945C.4020904@root.org>
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On Sun, Apr 10, 2005 at 02:02:20PM -0700, Nate Lawson wrote: > Kevin Oberman wrote: > >Nate, > > > >I finally had time to do some careful testing of power management on > >-current. All testing was done on my IBM T30 with a 1.8 GHz P4-M > >Processor. CPU load was generated by the use of md5 on a long gatch of > >zeros. (As you suggested.) > > > >First, on power dissipation, while the use of TCC and adjusting actual > >CPU frequency causes very predictable compute performance. They do not > >produce the expected matching power dissipation. > > > >Here is a chart of the CPU temperature against the value of > >dev.cpu.0.freq. The third column list the actual clock frequency that > >the CPU is using. The T30 supports only 2 frequencies, 1.8 GHz and 1.2 > >GHz. > > > >dev.cpu.0.freq Temperature CPU Clock > >1800 >_PSV 1800 > >1575 >_PSV 1800 > >1350 85 1800 > >1200 73 1200 > >1125 82 1800 > >1050 69 1200 > >900 77 1800 > >750 64 1200 > >675 72 1800 > >600 62 1200 > >450 66 1800 > >300 56 1200 > >225 61 1800 > >150 54 1200 > > > >As you can see, lowering the CPU cock speed is much more effective in > >reducing CPU heat (and battery drain) than doing it with TCC. I can get > >much better performance with lower battery consumption at 1200 MHz than > >at 900 MHz. Clearly, if both clock and TCC can provide identical > >performance, you want the slower clock. This is backwards from how it is > >now running as both 900 MHZ and 450 MHz can be achieved at either 1800 > >MHZ or 1200MHz clocking, but are clocked at 1800 MHz. > > Thanks for your testing. I agree that settings like the 900 mhz value > don't make sense to use when the 1050 value has lower heat. Do you have > known values for power consumption (sysctl dev.cpu.0.freq_levels, look > for the second number after the /)? Unknown values are marked -1. Is > the power consumption for 900 higher than 1050? If so, we could add a > test that compares power consumption and discards levels that have lower > frequencies but higher power consumption than their neighbors. What strange is that we got 900 = 1800 * .50, but I would expect 900 = 1200 * .75 since 0.75 is valid. -- Bruno Ducrot -- Which is worse: ignorance or apathy? -- Don't know. Don't care.
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