[Bug 54601] Re: disabling a CPU increases laptop power consumption

[Stuart Hopkins]

Sorry to bring this one back alive, but i'm actually finding this
problem still exists on Ubuntu 10.04 running the 2.6.32-24-generic-pae
kernel.

I'm running a W510 laptop (quad-core) with HT disabled, and to try and
save power (especially given the kernel interrupt problem atm) I tried
disabling 1/2/3 of the 4 cores. My logic behind it was that the core
would physically be powered down (no interrupts at all), and would use
little to no power.

In doing this, powertop informed me my idle power usage rose from 17W to
33W, not good on a laptop! I can reproduce this each time by disabling a
single or multiple cores. Also, if I re-enable them all, power usage
decreases.

Given how this kernel interface is designed to allow for a CPU to be
hotplugged in a live server, it seems strange in my mind that it is
still supplying power to it.

-- 
disabling a CPU increases laptop power consumption
https://bugs.launchpad.net/bugs/54601
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