On Fri, 2016-04-01 at 11:31 -0700, Doug Smythies wrote: > On 2106.034.01 10:45 Srinivas Pandruvada wrote: > > > > On Fri, 2016-04-01 at 16:06 +0200, Jörg Otte wrote: > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > Done. Attached the tracer. > > > For me it looks like the previous one of the failing case. > > The traces show that idle task is constantly running without sleep. > No, I mean atleast on once CPU. I am not saying they are looping, but the wakeup time is less than 10ms, so the driver will not scale the load for idle time.
> they (at least the first one, I didn't look at the next one yet) > show that CPUs 2 and 3 are spending around 99% of their time not in > state > C0. That the sample rate is ending up at ~10 Milliseconds, indicates > some > high frequency (>= 100Hz) events on those CPUs. Those events, > apparently, > take very little CPU time to complete, hence a load of about 1% on > average. > > By the way, I can recreate the high sample rate with virtually no > load > on my system easy, but so far have been unable to get the high CPU > frequencies observed by Jörg. I can get my system to about a target > pstate of > 20 where it should have remained at 16, but that is about it. > > > > > The driver is processing samples for idle task for every 10ms and > > aperf/mperf are showing that we are always in turbo mode for idle > > task. > That column pretty much always says "idle" (or swapper for my way of > doing > things). I have not found it to very useful as an indicator, and > considerably > more so since the utilization changes. > > > > > > > Need to find out why idle task is not sleeping. > I contend that is it. > I don't have enough reverted data, but so far this seems very much > like > that bug report I referenced earlier. > > ... Doug > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-pm" > in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html