On Tue, Jan 07, 2014 at 03:16:32PM +0000, Morten Rasmussen wrote: > From a load perspective wouldn't it be better to pick the least loaded > cpu in the group? It is not cheap to implement, but in theory it should > give less balancing within the group later an less unfairness until it > happens.
I tried that; see 04f733b4afac5dc93ae9b0a8703c60b87def491e for why it doesn't work. > Rotating the cpu is probably good enough for most cases and certainly > easier to implement. Indeed. > The bias continues after they first round of load balance by the other > cpus? The cost, yes. Even when perfectly balanced, we still get to iterate the entire machine computing s[gd]_lb_stats to find out we're good and don't need to move tasks about. > Pulling everything to one cpu is not ideal from a performance point of > view. You loose some available cpu cycles until the balance settles. > However, it is not easy to do better and maintain scalability at the > same time. Right, its part of the cost we pay for scaling better. And rotating this cost around a bit would alleviate the obvious bias. -- 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/
