diff options
Diffstat (limited to 'Documentation/cpu-freq')
| -rw-r--r-- | Documentation/cpu-freq/cpu-drivers.txt | 2 | ||||
| -rw-r--r-- | Documentation/cpu-freq/governors.txt | 26 | ||||
| -rw-r--r-- | Documentation/cpu-freq/user-guide.txt | 1 |
3 files changed, 15 insertions, 14 deletions
diff --git a/Documentation/cpu-freq/cpu-drivers.txt b/Documentation/cpu-freq/cpu-drivers.txt index 43c743903dd7..75a58d14d3cf 100644 --- a/Documentation/cpu-freq/cpu-drivers.txt +++ b/Documentation/cpu-freq/cpu-drivers.txt @@ -155,7 +155,7 @@ actual frequency must be determined using the following rules: - if relation==CPUFREQ_REL_H, try to select a new_freq lower than or equal target_freq. ("H for highest, but no higher than") -Here again the frequency table helper might assist you - see section 3 +Here again the frequency table helper might assist you - see section 2 for details. diff --git a/Documentation/cpu-freq/governors.txt b/Documentation/cpu-freq/governors.txt index ce73f3eb5ddb..aed082f49d09 100644 --- a/Documentation/cpu-freq/governors.txt +++ b/Documentation/cpu-freq/governors.txt @@ -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 diff --git a/Documentation/cpu-freq/user-guide.txt b/Documentation/cpu-freq/user-guide.txt index 75f41193f3e1..5d5f5fadd1c2 100644 --- a/Documentation/cpu-freq/user-guide.txt +++ b/Documentation/cpu-freq/user-guide.txt @@ -31,7 +31,6 @@ Contents: 3. How to change the CPU cpufreq policy and/or speed 3.1 Preferred interface: sysfs -3.2 Deprecated interfaces |