kernel module options for cpufreq

[Richard Hughes]

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?

Richard.