On Mon, Jun 24, 2013 at 12:32:00AM +0100, Benjamin Herrenschmidt wrote: > On Fri, 2013-06-21 at 14:34 -0700, Arjan van de Ven wrote: > > On 6/21/2013 2:23 PM, Catalin Marinas wrote: > > >> > > >> oops sorry I misread your mail (lack of early coffee I suppose) > > >> > > >> I can see your point of having a thing for "did we ask for all the > > >> performance > > >> we could ask for" prior to doing a load balance (although, for power > > >> efficiency, > > >> if you have two tasks that could run in parallel, it's usually better to > > >> run them in parallel... so likely we should balance anyway) > > > > > > Not necessarily, especially if parallel running implies powering up a > > > full cluster just for one CPU (it depends on the hardware but for > > > example a cluster may not be able to go in deeper sleep states unless > > > all the CPUs in that cluster are idle). > > > > I guess it depends on the system > > Sort-of. We have something similar with threads on ppc. IE, the core can > only really stop if all threads are. From a Linux persepctive it's a > matter of how we define the scope of that 'cluster' Catalin is talking > about. I'm sure you do too. > > Then there is the package, which adds MC etc...
I think we can say cluster == package so that we use some common terminology. On a big.little configuration (TC2), we have 3xA7 in one package and 2xA15 in the other. So to efficiently stop an entire package (cluster, multi-core etc.) we need to stop all the CPUs it has. -- 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/
