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Re: kernel module options for cpufreq



On Fri, 27 Jun 2008 17:13:24 +0100
Richard Hughes <hughsient gmail com> wrote:

> At the moment we set:
> 
> # CONFIG_CPU_FREQ_DEFAULT_GOV_PERFORMANCE is not set
> CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE=y
> # CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND is not set
> # CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE is not set
> CONFIG_CPU_FREQ_GOV_PERFORMANCE=y
> CONFIG_CPU_FREQ_GOV_POWERSAVE=m
> CONFIG_CPU_FREQ_GOV_USERSPACE=y
> CONFIG_CPU_FREQ_GOV_ONDEMAND=m
> CONFIG_CPU_FREQ_GOV_CONSERVATIVE=m
> 
> This is not ideal from a power-saving point of view.
> 
> In an ideal world we would:
> 
> * remove CONFIG_CPU_FREQ_GOV_CONSERVATIVE -- ondemand does a better
> job on all workloads
> * remove CONFIG_CPU_FREQ_GOV_USERSPACE -- we have nothing in
> userspace that needs this sort of control, and if we did, the latency
> would be horrible
> * remove CONFIG_CPU_FREQ_GOV_POWERSAVE -- ondemand automatically
> throttles down to lowest, and is just a hardcoded state
> * compile into the kernel CONFIG_CPU_FREQ_GOV_ONDEMAND -- we really
> want to be running this on all systems that support it
> * set ONDEMAND or PERFORMANCE to default as USERSPACE is just
> changed to something else by cpuspeed. You really don't want to be
> using USERSPACE at all.
> 
> Matthew Garrett and I are working on a latency profile for power
> management, and having all these modules potentially loaded is bad.
> 
> Comments?
> 

I totally agree with your suggestions.



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