On Fri, Apr 18, 2014 at 02:13:48PM +0200, Daniel Lezcano wrote: > On 04/18/2014 11:38 AM, Peter Zijlstra wrote: > >On Thu, Apr 17, 2014 at 12:21:28PM -0400, Nicolas Pitre wrote: > >>CPU topology is needed to properly describe scheduling domains. Whether > >>we balance across domains or pack using as few domains as possible is a > >>separate issue. In other words, you shouldn't have to care in this > >>patch series. > >> > >>And IMHO coupled C-state is a low-level mechanism that should remain > >>private to cpuidle which the scheduler shouldn't be aware of. > > > >I'm confused.. why wouldn't you want to expose these? > > The couple C-state is used as a mechanism for cpuidle to sync the cpus when > entering a specific c-state. This mechanism is usually used to handle the > cluster power down. It is only used for a two drivers (soon three) but it is > not the only mechanism used for syncing the cpus. There are also the MCPM > (tc2), the hand made sync when the hardware allows it (ux500), and an > abstraction from the firmware (mwait), transparent to the kernel. > > Taking into account the couple c-state only does not make sense because of > the other mechanisms above. This is why it should stay inside the cpuidle > framework. > > The extension of the cpu topology will provide a generic way to describe and > abstracting such dependencies. > > Does it answer your question ?
I suppose so; its still a bit like we won't but we will :-) So we _will_ actually expose coupled C states through the topology bits, that's good. -- 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/
