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[CPUFREQ] Only set sampling_rate_max deprecated, sampling_rate_min is useful

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Update the documentation accordingly.
Cleanup and use printk_once.

Signed-off-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Dave Jones <davej@redhat.com>
This commit is contained in:
Thomas Renninger
2009-04-22 13:48:31 +02:00
committed by Dave Jones
parent 86e13684aa
commit 4f4d1ad6ee
3 changed files with 18 additions and 43 deletions
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26
Documentation/cpu-freq/governors.txt
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@@ -119,10 +119,6 @@ want the kernel to look at the CPU usage and to make decisions on
what to do about the frequency. Typically this is set to values of
around '10000' or more. It's default value is (cmp. with users-guide.txt):
transition_latency * 1000
The lowest value you can set is:
transition_latency * 100 or it may get restricted to a value where it
makes not sense for the kernel anymore to poll that often which depends
on your HZ config variable (HZ=1000: max=20000us, HZ=250: max=5000).
Be aware that transition latency is in ns and sampling_rate is in us, so you
get the same sysfs value by default.
Sampling rate should always get adjusted considering the transition latency
@@ -131,14 +127,20 @@ in the bash (as said, 1000 is default), do:
echo `$(($(cat cpuinfo_transition_latency) * 750 / 1000)) \
>ondemand/sampling_rate
show_sampling_rate_(min|max): THIS INTERFACE IS DEPRECATED, DON'T USE IT.
You can use wider ranges now and the general
cpuinfo_transition_latency variable (cmp. with user-guide.txt) can be
used to obtain exactly the same info:
show_sampling_rate_min = transtition_latency * 500 / 1000
show_sampling_rate_max = transtition_latency * 500000 / 1000
(divided by 1000 is to illustrate that sampling rate is in us and
transition latency is exported ns).
show_sampling_rate_min:
The sampling rate is limited by the HW transition latency:
transition_latency * 100
Or by kernel restrictions:
If CONFIG_NO_HZ is set, the limit is 10ms fixed.
If CONFIG_NO_HZ is not set or no_hz=off boot parameter is used, the
limits depend on the CONFIG_HZ option:
HZ=1000: min=20000us (20ms)
HZ=250: min=80000us (80ms)
HZ=100: min=200000us (200ms)
The highest value of kernel and HW latency restrictions is shown and
used as the minimum sampling rate.
show_sampling_rate_max: THIS INTERFACE IS DEPRECATED, DON'T USE IT.
up_threshold: defines what the average CPU usage between the samplings
of 'sampling_rate' needs to be for the kernel to make a decision on