Merge branch 'tip/tracing/core' of git://git.kernel.org/pub/scm/linux/kernel/git...

[karo-tx-linux.git] / Documentation / cpu-freq / governors.txt

diff --git a/Documentation/cpu-freq/governors.txt b/Documentation/cpu-freq/governors.txt
index ce73f3eb5ddb1a99a1b4571d6e058ac5c9823765..737988fca64d37712a7b5c7dfc2d316a57be9082 100644 (file)
--- 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
@@ -131,20 +127,26 @@ 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
 whether it should increase the frequency.  For example when it is set
-to its default value of '80' it means that between the checking
-intervals the CPU needs to be on average more than 80% in use to then
+to its default value of '95' it means that between the checking
+intervals the CPU needs to be on average more than 95% in use to then
 decide that the CPU frequency needs to be increased.  
 
 ignore_nice_load: this parameter takes a value of '0' or '1'. When