Access CPU hotplug functionality from scheduler

[Haellis]

Hi,

I would like to be able to hotplug individual cores dynamically from the scheduler.

I am currently mucking about with the 2.6.35 kernel and i have tracked down the functin of interest, namely cpu_down() located in cpu.c

Now the problem is that when i try to call the function from inside the scheduler the whole system just freezes. No error messages no nothing.

My computer is a Lenovo thinkpad x201i with a core i3 cpu.
I have dual boot with win 7 and Ubuntu 10.10.

If anybodey has implemented some cpuhotplug functionality i would be grateful to know the correct way of doing this.

[Irithori]

Are you sure, you are looking at the right place?

CPU hotplugging is meant for server machines.
You physically remove a CPU from the motherboard, while the server is and stays up.
I cant think of a scenario, in which this can apply to a laptop.

[Haellis]

Im working on a University project where the idea it to se if cpu hotplugging could be used as a powersaving mechanism by dynamically turning off/on cores depending on the system load.
The laptop is only my "workstation" eventually I will try to target other machines. However first i must get the hotplug functionality to work from inside the scheduler or other appropriate place.

[Irithori]

Ah ok

I am not a dev, but fwiw this seems to be a start:
http://www.kernel.org/doc/Documentation/cpu-hotplug.txt

[Haellis]

Thanks, i have read the document a couple of times earlier and can't seem to find the solution to my problem. Of cource this does not mean it's not there, only that i can't see it :P. Iḿ not sure but i think i have some sort of a lock problem, regretably I have not been able to veryfie this much less locate it.