On Fri, Jan 5, 2018 at 9:37 PM, Leonard Crestez <leonard.cres...@nxp.com> wrote: > Hello, > > When using the schedutil governor together with the softlockup detector > all CPUs go to their maximum frequency on a regular basis. This seems > to be because the watchdog creates a RT thread on each CPU and this > causes regular kicks with: > > cpufreq_update_this_cpu(rq, SCHED_CPUFREQ_RT); > > The schedutil governor responds to this by immediately setting the > maximum cpu frequency, this is very undesirable. > > The issue can be fixed by this patch from android: > https://patchwork.kernel.org/patch/9301909/ > > The patch stalled in a long discussion about how it's difficult for > cpufreq to deal with RT and how some RT users might just disable > cpufreq. It is indeed hard but if the system experiences regular power > kicks from a common debug feature they will end up disabling schedutil > instead.
They are basically free to use the other governors instead if they prefer them. > No other governors behave this way, Because they work differently overall. > perhaps the current behavior should be considered a bug in schedutil. > > That patch now has conflicts with latest upstream. Perhaps a modified > variant should be reconsidered for inclusion, or is there some other > solution pending? Patrick has a series of patches dealing with this problem area AFAICS, but we are currently integrating material from Juri related to deadline tasks. > Alternatively the watchdog threads could be somehow marked as to never > cause increased cpufreq. Or maybe just replaced with something that is not a thread? RT really doesn't leave much choice, because it basically means "I'm important and I have a deadline, but I'm not telling you how important I am and what the deadline is". Thanks, Rafael
