lkml.org 
[lkml]   [2020]   [Dec]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRe: [PATCH V3 2/2] thermal: cpufreq_cooling: Reuse sched_cpu_util() for SMP platforms
Date

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

\
 
 \ /
  Last update: 2020-12-01 18:27    [W:0.112 / U:0.032 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site