Messages in this thread | | | From | Bill Davidsen <> | Subject | Re: SMP cpu deep sleep | Date | Mon, 23 Aug 2004 17:30:29 -0400 |
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Wes Felter wrote:
> I worked on this last year (I call it CPU packing, because the idea is to > pack the load onto the fewest number of CPUs). > > The CPU hotplug patch is the way to go, but the hardware is the problem. I > talked to an Intel CPU architect at MICRO last year and he confirmed that > SMP Intel systems don't support any low-power modes besides HLT. AMD's > documentation says that Opterons support voltage/frequency scaling (aka > Cool 'n' Quiet), but AFAICT the documentation is wrong. In summary, you > are doomed. >
For power saving, HLT is hard to beat ;-) You note HLT as if there was some good reason not to use it... Mask everything except some BACK2WORK int from the night watchman CPU. I would really like this on some machines which seem to leave all CPUs generating heat even when booted with a uni kernel.
Whilst thinking about this, *if* using HLT is practical in therms of power saving, perhaps all but the last CPU could HLT if the run queue was empty, and only be awakened by the "last" CPU, in some case where the run queue length was longer than {some_value}.
-- -bill davidsen (davidsen@tmr.com) "The secret to procrastination is to put things off until the last possible moment - but no longer" -me - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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