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![Rafael J. Wysocki](/assets/img/avatar_default.png)
Add a new cpufreq scaling governor, called "schedutil", that uses
scheduler-provided CPU utilization information as input for making
its decisions.
Doing that is possible after commit 34e2c555f3
(cpufreq: Add
mechanism for registering utilization update callbacks) that
introduced cpufreq_update_util() called by the scheduler on
utilization changes (from CFS) and RT/DL task status updates.
In particular, CPU frequency scaling decisions may be based on
the the utilization data passed to cpufreq_update_util() by CFS.
The new governor is relatively simple.
The frequency selection formula used by it depends on whether or not
the utilization is frequency-invariant. In the frequency-invariant
case the new CPU frequency is given by
next_freq = 1.25 * max_freq * util / max
where util and max are the last two arguments of cpufreq_update_util().
In turn, if util is not frequency-invariant, the maximum frequency in
the above formula is replaced with the current frequency of the CPU:
next_freq = 1.25 * curr_freq * util / max
The coefficient 1.25 corresponds to the frequency tipping point at
(util / max) = 0.8.
All of the computations are carried out in the utilization update
handlers provided by the new governor. One of those handlers is
used for cpufreq policies shared between multiple CPUs and the other
one is for policies with one CPU only (and therefore it doesn't need
to use any extra synchronization means).
The governor supports fast frequency switching if that is supported
by the cpufreq driver in use and possible for the given policy.
In the fast switching case, all operations of the governor take
place in its utilization update handlers. If fast switching cannot
be used, the frequency switch operations are carried out with the
help of a work item which only calls __cpufreq_driver_target()
(under a mutex) to trigger a frequency update (to a value already
computed beforehand in one of the utilization update handlers).
Currently, the governor treats all of the RT and DL tasks as
"unknown utilization" and sets the frequency to the allowed
maximum when updated from the RT or DL sched classes. That
heavy-handed approach should be replaced with something more
subtle and specifically targeted at RT and DL tasks.
The governor shares some tunables management code with the
"ondemand" and "conservative" governors and uses some common
definitions from cpufreq_governor.h, but apart from that it
is stand-alone.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
342 lines
10 KiB
Plaintext
342 lines
10 KiB
Plaintext
menu "CPU Frequency scaling"
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config CPU_FREQ
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bool "CPU Frequency scaling"
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select SRCU
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help
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CPU Frequency scaling allows you to change the clock speed of
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CPUs on the fly. This is a nice method to save power, because
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the lower the CPU clock speed, the less power the CPU consumes.
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Note that this driver doesn't automatically change the CPU
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clock speed, you need to either enable a dynamic cpufreq governor
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(see below) after boot, or use a userspace tool.
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For details, take a look at <file:Documentation/cpu-freq>.
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If in doubt, say N.
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if CPU_FREQ
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config CPU_FREQ_GOV_ATTR_SET
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bool
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config CPU_FREQ_GOV_COMMON
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select CPU_FREQ_GOV_ATTR_SET
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select IRQ_WORK
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bool
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config CPU_FREQ_BOOST_SW
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bool
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depends on THERMAL
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config CPU_FREQ_STAT
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tristate "CPU frequency translation statistics"
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default y
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help
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This driver exports CPU frequency statistics information through sysfs
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file system.
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To compile this driver as a module, choose M here: the
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module will be called cpufreq_stats.
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If in doubt, say N.
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config CPU_FREQ_STAT_DETAILS
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bool "CPU frequency translation statistics details"
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depends on CPU_FREQ_STAT
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help
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This will show detail CPU frequency translation table in sysfs file
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system.
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If in doubt, say N.
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choice
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prompt "Default CPUFreq governor"
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default CPU_FREQ_DEFAULT_GOV_USERSPACE if ARM_SA1100_CPUFREQ || ARM_SA1110_CPUFREQ
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default CPU_FREQ_DEFAULT_GOV_PERFORMANCE
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help
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This option sets which CPUFreq governor shall be loaded at
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startup. If in doubt, select 'performance'.
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config CPU_FREQ_DEFAULT_GOV_PERFORMANCE
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bool "performance"
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select CPU_FREQ_GOV_PERFORMANCE
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help
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Use the CPUFreq governor 'performance' as default. This sets
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the frequency statically to the highest frequency supported by
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the CPU.
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config CPU_FREQ_DEFAULT_GOV_POWERSAVE
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bool "powersave"
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select CPU_FREQ_GOV_POWERSAVE
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help
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Use the CPUFreq governor 'powersave' as default. This sets
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the frequency statically to the lowest frequency supported by
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the CPU.
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config CPU_FREQ_DEFAULT_GOV_USERSPACE
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bool "userspace"
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select CPU_FREQ_GOV_USERSPACE
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help
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Use the CPUFreq governor 'userspace' as default. This allows
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you to set the CPU frequency manually or when a userspace
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program shall be able to set the CPU dynamically without having
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to enable the userspace governor manually.
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config CPU_FREQ_DEFAULT_GOV_ONDEMAND
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bool "ondemand"
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select CPU_FREQ_GOV_ONDEMAND
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select CPU_FREQ_GOV_PERFORMANCE
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help
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Use the CPUFreq governor 'ondemand' as default. This allows
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you to get a full dynamic frequency capable system by simply
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loading your cpufreq low-level hardware driver.
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Be aware that not all cpufreq drivers support the ondemand
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governor. If unsure have a look at the help section of the
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driver. Fallback governor will be the performance governor.
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config CPU_FREQ_DEFAULT_GOV_CONSERVATIVE
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bool "conservative"
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select CPU_FREQ_GOV_CONSERVATIVE
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select CPU_FREQ_GOV_PERFORMANCE
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help
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Use the CPUFreq governor 'conservative' as default. This allows
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you to get a full dynamic frequency capable system by simply
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loading your cpufreq low-level hardware driver.
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Be aware that not all cpufreq drivers support the conservative
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governor. If unsure have a look at the help section of the
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driver. Fallback governor will be the performance governor.
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config CPU_FREQ_DEFAULT_GOV_SCHEDUTIL
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bool "schedutil"
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select CPU_FREQ_GOV_SCHEDUTIL
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select CPU_FREQ_GOV_PERFORMANCE
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help
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Use the 'schedutil' CPUFreq governor by default. If unsure,
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have a look at the help section of that governor. The fallback
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governor will be 'performance'.
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endchoice
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config CPU_FREQ_GOV_PERFORMANCE
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tristate "'performance' governor"
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help
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This cpufreq governor sets the frequency statically to the
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highest available CPU frequency.
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To compile this driver as a module, choose M here: the
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module will be called cpufreq_performance.
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If in doubt, say Y.
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config CPU_FREQ_GOV_POWERSAVE
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tristate "'powersave' governor"
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help
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This cpufreq governor sets the frequency statically to the
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lowest available CPU frequency.
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To compile this driver as a module, choose M here: the
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module will be called cpufreq_powersave.
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If in doubt, say Y.
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config CPU_FREQ_GOV_USERSPACE
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tristate "'userspace' governor for userspace frequency scaling"
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help
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Enable this cpufreq governor when you either want to set the
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CPU frequency manually or when a userspace program shall
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be able to set the CPU dynamically, like on LART
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<http://www.lartmaker.nl/>.
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To compile this driver as a module, choose M here: the
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module will be called cpufreq_userspace.
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For details, take a look at <file:Documentation/cpu-freq/>.
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If in doubt, say Y.
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config CPU_FREQ_GOV_ONDEMAND
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tristate "'ondemand' cpufreq policy governor"
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select CPU_FREQ_GOV_COMMON
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help
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'ondemand' - This driver adds a dynamic cpufreq policy governor.
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The governor does a periodic polling and
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changes frequency based on the CPU utilization.
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The support for this governor depends on CPU capability to
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do fast frequency switching (i.e, very low latency frequency
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transitions).
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To compile this driver as a module, choose M here: the
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module will be called cpufreq_ondemand.
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For details, take a look at linux/Documentation/cpu-freq.
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If in doubt, say N.
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config CPU_FREQ_GOV_CONSERVATIVE
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tristate "'conservative' cpufreq governor"
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depends on CPU_FREQ
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select CPU_FREQ_GOV_COMMON
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help
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'conservative' - this driver is rather similar to the 'ondemand'
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governor both in its source code and its purpose, the difference is
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its optimisation for better suitability in a battery powered
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environment. The frequency is gracefully increased and decreased
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rather than jumping to 100% when speed is required.
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If you have a desktop machine then you should really be considering
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the 'ondemand' governor instead, however if you are using a laptop,
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PDA or even an AMD64 based computer (due to the unacceptable
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step-by-step latency issues between the minimum and maximum frequency
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transitions in the CPU) you will probably want to use this governor.
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To compile this driver as a module, choose M here: the
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module will be called cpufreq_conservative.
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For details, take a look at linux/Documentation/cpu-freq.
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If in doubt, say N.
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config CPU_FREQ_GOV_SCHEDUTIL
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tristate "'schedutil' cpufreq policy governor"
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depends on CPU_FREQ
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select CPU_FREQ_GOV_ATTR_SET
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select IRQ_WORK
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help
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This governor makes decisions based on the utilization data provided
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by the scheduler. It sets the CPU frequency to be proportional to
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the utilization/capacity ratio coming from the scheduler. If the
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utilization is frequency-invariant, the new frequency is also
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proportional to the maximum available frequency. If that is not the
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case, it is proportional to the current frequency of the CPU. The
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frequency tipping point is at utilization/capacity equal to 80% in
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both cases.
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To compile this driver as a module, choose M here: the module will
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be called cpufreq_schedutil.
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If in doubt, say N.
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comment "CPU frequency scaling drivers"
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config CPUFREQ_DT
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tristate "Generic DT based cpufreq driver"
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depends on HAVE_CLK && OF
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# if CPU_THERMAL is on and THERMAL=m, CPUFREQ_DT cannot be =y:
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depends on !CPU_THERMAL || THERMAL
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select PM_OPP
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help
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This adds a generic DT based cpufreq driver for frequency management.
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It supports both uniprocessor (UP) and symmetric multiprocessor (SMP)
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systems which share clock and voltage across all CPUs.
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If in doubt, say N.
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if X86
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source "drivers/cpufreq/Kconfig.x86"
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endif
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if ARM || ARM64
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source "drivers/cpufreq/Kconfig.arm"
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endif
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if PPC32 || PPC64
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source "drivers/cpufreq/Kconfig.powerpc"
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endif
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if AVR32
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config AVR32_AT32AP_CPUFREQ
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bool "CPU frequency driver for AT32AP"
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depends on PLATFORM_AT32AP
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default n
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help
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This enables the CPU frequency driver for AT32AP processors.
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If in doubt, say N.
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endif
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if IA64
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config IA64_ACPI_CPUFREQ
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tristate "ACPI Processor P-States driver"
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depends on ACPI_PROCESSOR
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help
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This driver adds a CPUFreq driver which utilizes the ACPI
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Processor Performance States.
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For details, take a look at <file:Documentation/cpu-freq/>.
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If in doubt, say N.
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endif
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if MIPS
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config LOONGSON2_CPUFREQ
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tristate "Loongson2 CPUFreq Driver"
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help
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This option adds a CPUFreq driver for loongson processors which
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support software configurable cpu frequency.
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Loongson2F and it's successors support this feature.
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For details, take a look at <file:Documentation/cpu-freq/>.
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If in doubt, say N.
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config LOONGSON1_CPUFREQ
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tristate "Loongson1 CPUFreq Driver"
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help
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This option adds a CPUFreq driver for loongson1 processors which
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support software configurable cpu frequency.
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For details, take a look at <file:Documentation/cpu-freq/>.
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If in doubt, say N.
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endif
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if SPARC64
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config SPARC_US3_CPUFREQ
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tristate "UltraSPARC-III CPU Frequency driver"
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help
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This adds the CPUFreq driver for UltraSPARC-III processors.
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For details, take a look at <file:Documentation/cpu-freq>.
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If in doubt, say N.
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config SPARC_US2E_CPUFREQ
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tristate "UltraSPARC-IIe CPU Frequency driver"
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help
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This adds the CPUFreq driver for UltraSPARC-IIe processors.
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For details, take a look at <file:Documentation/cpu-freq>.
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If in doubt, say N.
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endif
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if SUPERH
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config SH_CPU_FREQ
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tristate "SuperH CPU Frequency driver"
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help
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This adds the cpufreq driver for SuperH. Any CPU that supports
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clock rate rounding through the clock framework can use this
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driver. While it will make the kernel slightly larger, this is
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harmless for CPUs that don't support rate rounding. The driver
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will also generate a notice in the boot log before disabling
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itself if the CPU in question is not capable of rate rounding.
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For details, take a look at <file:Documentation/cpu-freq>.
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If unsure, say N.
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endif
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config QORIQ_CPUFREQ
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tristate "CPU frequency scaling driver for Freescale QorIQ SoCs"
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depends on OF && COMMON_CLK && (PPC_E500MC || ARM)
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depends on !CPU_THERMAL || THERMAL
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select CLK_QORIQ
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help
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This adds the CPUFreq driver support for Freescale QorIQ SoCs
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which are capable of changing the CPU's frequency dynamically.
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endif
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endmenu
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