On 31/05/17 12:30, Peter Zijlstra wrote: > On Wed, May 31, 2017 at 11:40:47AM +0200, Peter Zijlstra wrote: > > On Wed, May 24, 2017 at 11:00:51AM +0200, Vincent Guittot wrote: > > > schedutil governor relies on cfs_rq's util_avg to choose the OPP when cfs > > > tasks are running. When the CPU is overloaded by cfs and rt tasks, cfs > > > tasks > > > are preempted by rt tasks and in this case util_avg reflects the remaining > > > capacity that is used by cfs tasks but not what cfs tasks want to use. In > > > such > > > case, schedutil can select a lower OPP when cfs task runs whereas the CPU > > > is > > > overloaded. In order to have a more accurate view of the utilization of > > > the > > > CPU, we track the utilization that is used by RT tasks. > > > DL tasks are not taken into account as they have their own utilization > > > tracking mecanism. > > > > Well, the DL tracking is fairly pessimistic; it assumes all DL tasks > > will consume their total budget, which will rarely, if ever, happen. > > > > So I suspect it might well be worth it to also track DL activity for the > > purpose of compensating CFS. > > Again, it seems I have this CPPC/HWP crud firmly stuck in my brain. > Because I was thinking: > > min_freq = dl_util > avg_freq = dl_avg + rt_avg + cfs_util > > > But given we don't actually have that split... meh. >
Right, interesting. So, I guess the question is: should we have it? :) IMHO, it makes sense and seems to benefit mobile use-cases I'm looking at. rt_avg though it also seems to build up very slowly (at least with default configs). I'm experimenting with Vincent proposal and it looks better (w.r.t. using rt_avg). Also summing up signals that behave similarly doesn't seem the wrong thing to do.
