Messages in this thread | | | From | Valentin Schneider <> | Subject | Re: [PATCH V3 2/2] thermal: cpufreq_cooling: Reuse sched_cpu_util() for SMP platforms | Date | Tue, 01 Dec 2020 17:25:46 +0000 |
| |
Hi Viresh,
On 19/11/20 07:38, Viresh Kumar wrote: > As can be clearly seen, the load and requested_power numbers are simply > incorrect in the idle time based approach and the numbers collected from > CPU's utilization are much closer to the reality. >
PELT time-scaling can make the util signals behave strangely from an external PoV. For instance, on a big.LITTLE system, the rq util of a LITTLE CPU may suddenly drop if it was stuck on a too-low OPP for some time and eventually reached the "right" OPP (i.e. got idle time).
Also, as Peter pointed out in [1], task migrations can easily confuse an external observer that considers util to be "an image of the recent past".
This will need testing on asymmetric CPU capacity systems, IMO.
[1]: https://lore.kernel.org/r/20201120075527.GB2414@hirez.programming.kicks-ass.net
| |