On Wed, Jun 04, 2014 at 10:23:13AM +0100, Peter Zijlstra wrote: > > f you had five tasks on one cpu that each have a 25% requirement you can > > get individual task runnable_avgs of up to 100% (cpu unweighted > > runnable_load_avg can get up 500%, I think), but the task running_avgs > > would be 20% each (total of 100%). > > Yeah, more or less so indeed. I had not considered the queueing effects > on runnable_avg yesterday, so good that that got raised. > > That does indeed invalidate my: runnable - running := extra cpu required > thing. It ends up being the extra cpu required for 0 latency but gobs of > idle time, which is something else entirely.
Agreed, but I think it is still a useful estimate of the required compute capacity. If there is a significant difference between runnable and running on a cpu, the current mix of tasks is not good for latency. However, we need to treat it as a worst case estimate and not necessarily try to move exactly runnable-running worth of tasks to another cpu. So far I haven't been able to come up with something better. -- 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/
