An Update On The Linux Power Situation In Ubuntu
The Sandy Bridge notebook in use is the HP EliteBook used in many Phoronix tests with the Intel Core i5 2520M and the integrated Intel HD graphics. This CPU does support EPB and is indicated so by /proc/cpuinfo. On the latest Oneiric kernel, ENERGY_PERF_BIAS being set to "normal" is also indicated from the dmesg output. This Sandy Bridge system was running the latest Ubuntu Oneiric packages as of 7 October.
This testing is comparing the Linux 3.0 and 3.0.1 vanilla kernels to the latest kernel found in Oneiric (3.0.0-12-generic) and when PCI Express Active State Power Management is forced.
The battery power usage test profile does indicate the power usage going down in the 3.0.1 and Oneiric kernels by a small amount. Unfortunately, since Sandy Bridge is not well supported in the 2.6.38 and earlier kernels, there are not power consumption results that can be looked at going far back. When ASPM was forced, the power usage was at its lowest point, but there is not much of a difference due to the use of integrated graphics (rather than a discrete GPU that could use ASPM) and Sandy Bridge already being quite power efficient.
With OpenArena, the 3.0.1 and Oneiric kernels did drop by about one Watt on average for their power consumption while running this OpenArena game.
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