powerd / cpufreq question

Alexander Motin mav at FreeBSD.org
Sat Apr 9 15:29:28 UTC 2011


On 09.04.2011 17:39, Bartosz Fabianowski wrote:
> I just noticed this thread a day after my own fight with powerd and load
> percentages that did not seem to make any sense.
>
> The patch I came up with is attached. It modifies powerd to use the load
> percentage of the busiest core. This reduces the range of values back to
> 0%...100% also for multi-core systems.

While using maximum of loads can be better then using levels above 100%, 
it won't properly handle cases of dependent or frequently migrating 
threads, that are handled now with summary load and levels less then 
100%. While existing powerd algorithm is indeed not perfect, it is the 
only relatively performance-safe, unlike others propositions.

I won't argue about adding more algorithms/options to powerd, optimized 
for handling different situations, but I believe that default should 
remain safe.

> On my Core i7 setup here, the change seems to work well.

... in your specific workload. And you haven't described how you 
measured system performance to prove that it haven't decreased.

-- 
Alexander Motin


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