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. In fact, I don't think you particularly care about RT here, as anything !CFS that preempts it, including those interrupts you mentioned. Which gets us back to what rt_avg is. > We don't use rt_avg which doesn't have the same dynamic as PELT and which > can include IRQ time that are also accounted in cfs task utilization Well, if rt_avg includes IRQ time, then that IRQ time is not part of the task clock. > Signed-off-by: Vincent Guittot <[email protected]> > --- > > If the changes are reasonnable, it might worth moving the PELT function in a > dedicated pelt.c file and the ugly > extern int update_rt_rq_load_avg(u64 now, int cpu, struct rt_rq *rt_rq, int > running); > in a pelt.h header > > > kernel/sched/fair.c | 21 +++++++++++++++++++++ > kernel/sched/rt.c | 9 +++++++++ > kernel/sched/sched.h | 3 +++ > 3 files changed, 33 insertions(+) Also, and I didn't check this, it is important that the windows are aligned if you want to sum the values.
