RE: [PATCH] 3/3 Dynamic cpufreq governor and updates to ACPIP-state driver

[Nakajima, Jun]

> 
> it's all nice code and such, but I still wonder why this can't be done
> by a userland policy daemon. The 2.6 kernel has the infrastructure to
> give very detailed information to userspace (eg top etc) about idle
> percentages...... I didn't see anything in this driver that couldn't
be
> done from userspace.
> 

It's about the frequency of the feedback loop. As we have much lower
latency with P-state transitions, the sampling time can be order of
millisecond (or shorter if meaningful). A userland daemon can have a
high-level policy (preferences, or set of parameters), but it cannot be
part of the real feedback loop. If we combine P-state transitions and
deeper C-state transitions, the situation is worse with a userland
daemon.

	Jun








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