cpufreq governor vs. powernowd

[Matt Zimmerman]

On Fri, Aug 18, 2006 at 12:41:58PM -0400, Dmitriy Kropivnitskiy wrote:
> I have found an article titled "How To Make Firefox Over 40% Faster"
> In essence, the title couldn't be more wrong, the author is actually 
> talking about replacing user space daemon powernowd with "on demand" 
> kernel space governor. The title stems from the fact that the author 
> uses firefox render speed to benchmark. But one of the points seems very 
> logical. The kernel space governor can poll the cpu levels much more 
> frequently causing much lower overhead, thus making the system more 
> responsive to sudden load increases, such as application start. 
> Additionally this way we can get rid of one more "start by default from 
> default install" daemon, which is IMHO always a good thing. In short, 
> what I propose is:
> 
> 1. Remove powernowd from the default install or change the startup 
> script not to start it by default.
> 2. Add sysfsutils to the default install
> 3. Make "on demand" governer teh default.
> 4. Leave loading a proper cpufreq driver as an exercise for the user, 
> same as it is right now (would be nice to auto detect and load an 
> appropriate module, but that is a separate problem)

The trouble with your proposal is that ondemand doesn't work everywhere that
the userspace governor does, according to Matthew Garrett.  I have some code
locally which attempts to activate it and falls back to userspace/powernowd
if it doesn't work, but I haven't tested it yet and it isn't clear that we
can always detect this situation.

-- 
 - mdz