Re: So, what's the status on the recent patches here?

Amit Kucheria
2006-08-18T11:48:39Z

On Thu, 2006-08-17 at 21:40 +0000, ext Pavel Machek wrote:

> > The userspace interface in Eungeny's patches is for other userspace
> > programs (policy managers) to activate/deactivate valid operating points
> > in the system dynamically and if necessary, introduce new ones into the
> > system. It will also allow the operating points to be referenced by name
> > instead of the tuple.
> >
> > Then, we will be able to use names like 'video', 'mp3', 'fast',
> > 'powersave', 'usb' to switch to the relevant operating point based on
> > configuration of the policy manager.
>
> This seems to be too specific to embedded machine.
>
> If userspace wants to work with usb and play mp3s at the same time,
> what does it do?

Switch to 'fast'?

The operating point for a use-case specifies the _minimum_ required for
the use-case. You can always go up.

The system designer is responsible for 'designing' operating points that
take into account multiple use-cases. Designing here refers to mapping
use-cases to HW operating points.

Consider an example system with a main CPU and a DSP. To simplify
discussion, lets assume 3 levels for CPU and DSP speeds and system
voltage. Then, here is what an example operating-point to use-case
mapping table could look like:

# CPU speed DSP speed Voltage use-case
----------------------------------------------------------
1. high high high fast, video
2. med high high
3. med med med usb[1]
4. low med med mp3
5. low low low powersave

[1] USB has voltage constraint (voltage >= med)

Mapping
=======
Performance related: fast, video, mp3
Power related: powersave
Miscellaneous: usb

- Now if we are playing mp3, we switch to OP 4.
- Add usb and we switch to OP 3.
- Now our performance monitor (e.g load avg) indicates that we need more
CPU processing. So we switch to OP 2.

Regards,
Amit

--
Amit Kucheria <amit.kucheria@nokia.com>
Nokia