On Friday, July 20, 2012, Tejun Heo wrote: > Hello, > > On Fri, Jul 20, 2012 at 08:22:30PM +0200, Peter Zijlstra wrote: > > I really think people who use hotplug at high frequencies are on drugs > > and doing it wrong. > > I don't know. It does make some sense. It's not like we have any > other mechanism to keep some processors completely quiesient, which > could make a noticeable difference from powersaving POV compared to > mostly idle. Rafael, can you please chime in and explain how / where > / how freqeuntly / etc CPU hotplug is used for powersaving?
Well, there are use cases I'm not really familiar with. Pretty much the only use case I'm sufficiently familiar with is suspend/hibernate where we unplug all of the nonboot CPUs at one point. The other use cases, which I don't really think are entirely valid, are on some ARM platforms where CPUs are unplugged instead of being put into C-states or equivalent (because we don't have a good mechanism for handling multiprocessor C-states; there's a set of patches for that waiting for the merge window in the Len's tree). I'm hoping to get rid of those use cases in future entirely. Thanks, Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
