On 11 Nov 2013, at 19:26, Arjan van de Ven <ar...@linux.intel.com> wrote: > On 11/11/2013 10:31 AM, Catalin Marinas wrote: >> I agree, we can't rely on the requested C-state but the_actual_ state >> and this means querying the hardware driver. Can we abstract this via >> some interface which provides the cost of waking up a CPU? This could >> take into account the state of the other CPUs in the cluster and the >> scheduler is simply concerned with the wake-up costs. > > can you even query this without actually waking up the cpu and asking ???
Even if you don’t have additional hardware to query the state of a CPU without waking it up, we could have a per-CPU variable storing the actual C-states as selected by the arch backend. This doesn’t need to be precise but lets say only 90% accurate would probably be enough for the scheduler. Catalin-- 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/
