Re: [Dynamicpower-devel] Thread dpmstate support

[Patrick B. <der...@gm...>]

> Sounds like a good feature: to the extent per-process power states are
> useful, it really should be implemented per-thread. 
Fortunately, since linux implement thread as LWP, the dpmstate info embedded 
within the task_struct is available for threads too. Threads already inherit 
dpmstate from their thread leader... anyway the procfs DPM interface doesn't 
export that param for task but just for processes. The simple patch I've 
posted previously add that feature so that we find a dpmstate attrib even 
within proc task subdirs.

> From what I've 
> seen of DPM implementations, the per-process power states haven't been
> heavily used for whatever reason, possibly that assigning
> power/performance tradeoffs to particular processes is an advanced
> topic and most folks are primarily concerned with the basics.
Me I'm just investigating on those issues.... and I confirm: it's not trivial.
The main issue we are focusing is how to "understand" power/performances 
threadoff for each process. The idea up-to-now is to try infering that 
information by looking at how processes "use" OS services...
Another issue is related to overhead compensation: how much frequently we 
could change OP without losing benefits of operating at the best OP for each 
task.

> It would be interesting to see a usage of per-thread power states.

Regards,
   Patrick


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