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cpufreq: docs: Reflect latency changes in docs

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There were two changes related to transition latency recently.
Namely commit e13aa799c2 ("cpufreq: Change default transition delay
to 2ms") and
commit 37c6dccd68 ("cpufreq: Remove LATENCY_MULTIPLIER").

Both changed the defaults / maximums so let the documentation
reflect that.

Signed-off-by: Christian Loehle <christian.loehle@arm.com>
Link: https://patch.msgid.link/46853b6e-bad5-4ace-9b23-ff157f234ae3@arm.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Christian Loehle 2024-10-17 23:00:33 +01:00 committed by Rafael J. Wysocki
parent 42f7652d3e
commit 29dcbea924
1 changed files with 10 additions and 10 deletions
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20
Documentation/admin-guide/pm/cpufreq.rst
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@ -425,8 +425,8 @@ This governor exposes only one tunable:
``rate_limit_us``
Minimum time (in microseconds) that has to pass between two consecutive
runs of governor computations (default: 1000 times the scaling driver's
transition latency).
runs of governor computations (default: 1.5 times the scaling driver's
transition latency or the maximum 2ms).
The purpose of this tunable is to reduce the scheduler context overhead
of the governor which might be excessive without it.
@ -474,17 +474,17 @@ This governor exposes the following tunables:
This is how often the governor's worker routine should run, in
microseconds.
Typically, it is set to values of the order of 10000 (10 ms). Its
default value is equal to the value of ``cpuinfo_transition_latency``
for each policy this governor is attached to (but since the unit here
is greater by 1000, this means that the time represented by
``sampling_rate`` is 1000 times greater than the transition latency by
default).
Typically, it is set to values of the order of 2000 (2 ms). Its
default value is to add a 50% breathing room
to ``cpuinfo_transition_latency`` on each policy this governor is
attached to. The minimum is typically the length of two scheduler
ticks.
If this tunable is per-policy, the following shell command sets the time
represented by it to be 750 times as high as the transition latency::
represented by it to be 1.5 times as high as the transition latency
(the default)::
# echo `$(($(cat cpuinfo_transition_latency) * 750 / 1000)) > ondemand/sampling_rate
# echo `$(($(cat cpuinfo_transition_latency) * 3 / 2)) > ondemand/sampling_rate
``up_threshold``
If the estimated CPU load is above this value (in percent), the governor