On Tue, Jun 03, 2014 at 04:50:07PM +0100, Peter Zijlstra wrote: > On Wed, May 28, 2014 at 04:47:03PM +0100, Morten Rasmussen wrote: > > Since we may do periodic load-balance every 10 ms or so, we will perform > > a number of load-balances where runnable_avg_sum will mostly be > > reflecting the state of the world before a change (new task queued or > > moved a task to a different cpu). If you had have two tasks continuously > > on one cpu and your other cpu is idle, and you move one of the tasks to > > the other cpu, runnable_avg_sum will remain unchanged, 47742, on the > > first cpu while it starts from 0 on the other one. 10 ms later it will > > have increased a bit, 32 ms later it will be 47742/2, and 345 ms later > > it reaches 47742. In the mean time the cpu doesn't appear fully utilized > > and we might decide to put more tasks on it because we don't know if > > runnable_avg_sum represents a partially utilized cpu (for example a 50% > > task) or if it will continue to rise and eventually get to 47742. > > Ah, no, since we track per task, and update the per-cpu ones when we > migrate tasks, the per-cpu values should be instantly updated.
No, not for this per-cpu tracking metric :) For cfs.runnable_load_avg you are right, but this patch set is using rq->avg.runnable_avg_sum which is different. See my other reply. > If we were to increase per task storage, we might as well also track > running_avg not only runnable_avg. That could probably make sense. We had that in pjt's first proposal. -- 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/
