On 12 June 2018 at 11:20, Quentin Perret <quentin.per...@arm.com> wrote: > On Tuesday 12 Jun 2018 at 11:16:56 (+0200), Vincent Guittot wrote: >> The time spent under interrupt can be significant but it is not reflected >> in the utilization of CPU when deciding to choose an OPP. Now that we have >> access to this metric, schedutil can take it into account when selecting >> the OPP for a CPU. >> rqs utilization don't see the time spend under interrupt context and report >> their value in the normal context time window. We need to compensate this >> when >> adding interrupt utilization >> >> The CPU utilization is : >> irq util_avg + (1 - irq util_avg / max capacity ) * /Sum rq util_avg >> >> A test with iperf on hikey (octo arm64) gives: >> iperf -c server_address -r -t 5 >> >> w/o patch w/ patch >> Tx 276 Mbits/sec 304 Mbits/sec +10% >> Rx 299 Mbits/sec 328 Mbits/sec +09% >> >> 8 iterations >> stdev is lower than 1% >> Only WFI idle state is enable (shallowest diel state) > ^^^^ > nit: s/diel/idle > > And, out of curiosity, what happens if you leave the idle states > untouched ? Do you still see an improvement ? Or is it lost in the > noise ?
the result are less stable because c-state wake up time impact performance and cpuidle is not good to select the right idle state in such case. Normally, an app should use qos dma latency or a driver per device resume latency > > Thanks, > Quentin