cpuidle: add a sysfs entry to disable specific C state for debug purpose.

Some C states of new CPU might be not good.  One reason is BIOS might
configure them incorrectly.  To help developers root cause it quickly, the
patch adds a new sysfs entry, so developers could disable specific C state
manually.

In addition, C state might have much impact on performance tuning, as it
takes much time to enter/exit C states, which might delay interrupt
processing.  With the new debug option, developers could check if a deep C
state could impact performance and how much impact it could cause.

Also add this option in Documentation/cpuidle/sysfs.txt.

[[email protected]: check kstrtol return value]
Signed-off-by: ShuoX Liu <[email protected]>
Reviewed-by: Yanmin Zhang <[email protected]>
Reviewed-and-Tested-by: Deepthi Dharwar <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Len Brown <[email protected]>
This commit is contained in:
ShuoX Liu 2012-03-28 15:19:11 -07:00 • committed by Len Brown
commit 3a53396b03
5 changed files with 51 additions and 1 deletions

View file

@ -36,6 +36,7 @@ drwxr-xr-x 2 root root 0 Feb 8 10:42 state3
/sys/devices/system/cpu/cpu0/cpuidle/state0:
total 0
-r--r--r-- 1 root root 4096 Feb 8 10:42 desc
-rw-r--r-- 1 root root 4096 Feb 8 10:42 disable
-r--r--r-- 1 root root 4096 Feb 8 10:42 latency
-r--r--r-- 1 root root 4096 Feb 8 10:42 name
-r--r--r-- 1 root root 4096 Feb 8 10:42 power
@ -45,6 +46,7 @@ total 0
/sys/devices/system/cpu/cpu0/cpuidle/state1:
total 0
-r--r--r-- 1 root root 4096 Feb 8 10:42 desc
-rw-r--r-- 1 root root 4096 Feb 8 10:42 disable
-r--r--r-- 1 root root 4096 Feb 8 10:42 latency
-r--r--r-- 1 root root 4096 Feb 8 10:42 name
-r--r--r-- 1 root root 4096 Feb 8 10:42 power
@ -54,6 +56,7 @@ total 0
/sys/devices/system/cpu/cpu0/cpuidle/state2:
total 0
-r--r--r-- 1 root root 4096 Feb 8 10:42 desc
-rw-r--r-- 1 root root 4096 Feb 8 10:42 disable
-r--r--r-- 1 root root 4096 Feb 8 10:42 latency
-r--r--r-- 1 root root 4096 Feb 8 10:42 name
-r--r--r-- 1 root root 4096 Feb 8 10:42 power
@ -63,6 +66,7 @@ total 0
/sys/devices/system/cpu/cpu0/cpuidle/state3:
total 0
-r--r--r-- 1 root root 4096 Feb 8 10:42 desc
-rw-r--r-- 1 root root 4096 Feb 8 10:42 disable
-r--r--r-- 1 root root 4096 Feb 8 10:42 latency
-r--r--r-- 1 root root 4096 Feb 8 10:42 name
-r--r--r-- 1 root root 4096 Feb 8 10:42 power
@ -72,6 +76,7 @@ total 0
* desc : Small description about the idle state (string)
* disable : Option to disable this idle state (bool)
* latency : Latency to exit out of this idle state (in microseconds)
* name : Name of the idle state (string)
* power : Power consumed while in this idle state (in milliwatts)