On Fri, Jan 22, 2021 at 09:40:38PM +0100, Giovanni Gherdovich wrote: > 1. PROBLEM DESCRIPTION (over-utilization and schedutil) > > The problem happens on CPU-bound workloads spanning a large number of cores. > In this case schedutil won't select the maximum P-State. Actually, it's > likely that it will select the minimum one. > > A CPU-bound workload puts the machine in a state generally called > "over-utilization": an increase in CPU speed doesn't result in an increase of > capacity. The fraction of time tasks spend on CPU becomes constant regardless > of clock frequency (the tasks eat whatever we throw at them), and the PELT > invariant util goes up and down with the frequency (i.e. it's not invariant > anymore).
> v5.10 v5.11-rc4 > ~~~~~~~~~~~~~~~~~~~~~~~~ > CPU activity (mpstat) 80-90% 80-90% > schedutil requests (tracepoint) always P0 mostly P2 > CPU frequency (HW feedback) ~2.2 GHz ~1.5 GHz > PELT root rq util (tracepoint) ~825 ~450 > > mpstat shows that the workload is CPU-bound and usage doesn't change with So I'm having trouble with calling a 80%-90% workload CPU bound, because clearly there's a ton of idle time.
