Fair enough, and I have to fully agree, it's better to have a power
management which consumes a bit more than the unreachable optimal, than
having everyone switch it off completely.
Yes, but keep in mind the Linux ondemand governor should not be tweaked
only for the latest Intel CPUs. I've just done a very little and
_extremely rough_ measurement on my laptop with a Core Duo 2, and while
it seems that, indeed, at idle the frequency didn't matter for the
consumption (about 12.5W with any governor), when running updatedb (so
IO bound), the performance governor seems to consume more than ondemand
and powersave (14.8-15.8W instead of 14.0-14.6W). I'm very careful with
the results of this "experiment" because it's only using the ACPI report
for the power usage and done with many other programs in the background.
Nevertheless, it manages to convince me that this change is not going to
be as harmless for the power consumption as you suggest.
Don't take me wrong. Here, I'm not saying that this patch is bad per se.
In particular, I do understand the specific workloads it tries to
handle, and I don't have a better solution for it in mind. However, this
is quite a change in the ondemand governor logic, and the log message do
not mention anything about energy consumption. This triggers a big
warning "only half of the problem was looked at to get a solution"!
So if this patch ever goes in, it should at least have a better
changelog which describes what are the potential consequences on the
power consumption.
Cheers,
Eric
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