kernel module options for cpufreq

[Dave Jones]

On Fri, Jun 27, 2008 at 05:13:24PM +0100, Richard Hughes 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

needed for the cpuspeed governor

 > * 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.

Not all CPUs are capable of running ondemand because of the latency they
incur during transitions.
 
 > Matthew Garrett and I are working on a latency profile for power
 > management, and having all these modules potentially loaded is bad.

I don't follow this.  Can you show whatever numbers you have that you're
basing this on ?

	Dave

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