Re: [gpm] New preferences UI

[Holger Macht <hmacht suse de>]

On Mon 18. Dec - 23:30:20, Richard Hughes wrote:
> On Tue, 2006-12-19 at 00:16 +0100, Holger Macht wrote:
> > On Mon 18. Dec - 21:12:13, Richard Hughes wrote:
> > > On Mon, 2006-12-18 at 20:52 +0000, Matthew Garrett wrote:
> > > > On Sat, Dec 16, 2006 at 01:58:19PM +0000, Richard Hughes wrote:
> > > > > On Thu, 2006-12-14 at 21:16 +0000, Matthew Garrett wrote:
> > > > > > Hi,
> > > > > > 
> > > > > > I've been playing with the new preferences UI in the 2.17 releases, and 
> > > > > > so far I'm not especially keen.
> > > > > 
> > > > > Have a look that the attached image.
> > > > 
> > > > That's definitely better, but it still seems to have support for setting 
> > > > the CPUfreq governer. On any modern hardware, what's the use case for 
> > > > this being anything other than ondemand?
> > > 
> > > Well, I for one get a >200ms latency when I click the menus (i.e. less
> > > snappy) when I'm scaled down to 1GHz - and I've noticed conservative and
> > > ondemand take quite a while to "ramp up" when the cpu load goes up. Some
> > > people might also not want the computer to scale at all.
> > 
> > As Mattthew already said, you shouldn't notice a significant amount of
> > time when frequency increases. Otherwise there's definitely something
> > wrong on your machine ;-)
> 
> Hmm. Maybe it's my brain playing to a preconceived idea. :-)
> 
> > > Maybe these are all just excuses - maybe we should just say
> > > "ondemand" (or conservative if available) for battery power, and
> > > "performance" on AC. It would sure make the difficult to explain problem
> > > option in the UI unnecessary.
> > > 
> > > What does everyone else think?
> > 
> > Using fixed frequency is always bad idea. That's why there's this
> > 'performance setting' for all dynamic governors in the hal cpufreq
> > addon. I think it's just enough to always use ondemand, with different
> > performance settings for AC (e.g. 25) and battery (e.g. 75).
> 
> I didn't know you could adjust the ondemand or conservative schedulers.
> What does the performance setting do?

It's written down in the HAL spec or a little bit more detailed at [1]. In
a few words, the higher the performance setting, the faster and the sooner
the frequency is switched up. And it's independent from the governor used
as long as it is one of the dynamic ones (userspace, ondemand).

> 
> > What I thought about for kpowersave was (not sure if I'll do it):
> > 
> >   Only show a slider for CPU policy
> > 
> >   1 --------------- 50 --------------- 100
> > 
> >   Everything between 2 and 99 just sets the performance setting for the
> >   current dynamic governor. If the user sets it to 1, powersave governor
> >   is used, if set to 100, performance governor is used.
> > 
> > But it should be completely fine to just always set the ondemand governor
> > with predefined performance values. A gconf key would be fine, though.
> 
> Sure, that's the way I'm now erring.
> 
> > And please note, once in a while the conservative governor gets very bad
> > press on the kernel lists. So in its current state, I discourage everybody
> > to use it.
> 
> Ohh, right. I was under the impression that conservative was the same as
> ondemand with a longer "hold time" after a high cpu load - how else is
> it different?

It's quite similar to ondemand, but uses a more passive switching
algorithm. For instance, it does traverse more steps and remains longer at
one step until reaching max freq. Same for decreasing frequency.

Personally I would suggest to use the userspace governor with the hal
addon if you like to have a policy near to conservative. In my opinion,
ondemand should be fine in all cases, though.

Regards,
	Holger

[1] http://blog.homac.de/?p=42