On Tue, Nov 24, 2015 at 02:49:30PM +0100, Vincent Guittot wrote: > Instead of scaling the complete value of PELT algo, we should only scale > the running time by the current capacity of the CPU. It seems more correct > to only scale the running time because the non running time of a task > (sleeping or waiting for a runqueue) is the same whatever the current freq > and the compute capacity of the CPU.
So I'm leaning towards liking this; however with your previous example of 3 cpus and 7 tasks, where CPU0-1 are 'little' and of half the capacity as the 'big' CPU2, with 2 tasks on CPU0-1 each and 3 tasks on CPU2. This would result, for CPU0, in a load of 100% wait time + 100% runtime, scaling the runtime 50% will get you a total load of 150%. For CPU2 we get 100% runtime and 200% wait time, no scaling, for a total load of 300%. So the CPU0-1 cluster has a 300% load and the CPU2 'cluster' has a 300% load, even though the actual load is not actually equal, CPUs0-1 combined have the same capacity as CPU2, so it should be 4-4 tasks for an equal balance. So I'm not sure the claim of comparable between CPUs stands. Still it is an interesting idea and I will consider it more. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
