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author | Carsten Emde <C.Emde@osadl.org> | 2012-07-19 20:34:10 +0000 |
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committer | Rafael J. Wysocki <rjw@sisk.pl> | 2012-09-04 01:35:44 +0200 |
commit | 62d6ae880e3e76098d5e345decd2dce443975889 (patch) | |
tree | 5788868e10c08030c5981adae8f5dfd6306b2608 /drivers/nubus/proc.c | |
parent | 4cbe5a555fa58a79b6ecbb6c531b8bab0650778d (diff) | |
download | talos-op-linux-62d6ae880e3e76098d5e345decd2dce443975889.tar.gz talos-op-linux-62d6ae880e3e76098d5e345decd2dce443975889.zip |
Honor state disabling in the cpuidle ladder governor
There are two cpuidle governors ladder and menu. While the ladder
governor is always available, if CONFIG_CPU_IDLE is selected, the
menu governor additionally requires CONFIG_NO_HZ.
A particular C state can be disabled by writing to the sysfs file
/sys/devices/system/cpu/cpuN/cpuidle/stateN/disable, but this mechanism
is only implemented in the menu governor. Thus, in a system where
CONFIG_NO_HZ is not selected, the ladder governor becomes default and
always will walk through all sleep states - irrespective of whether the
C state was disabled via sysfs or not. The only way to select a specific
C state was to write the related latency to /dev/cpu_dma_latency and
keep the file open as long as this setting was required - not very
practical and not suitable for setting a single core in an SMP system.
With this patch, the ladder governor only will promote to the next
C state, if it has not been disabled, and it will demote, if the
current C state was disabled.
Note that the patch does not make the setting of the sysfs variable
"disable" coherent, i.e. if one is disabling a light state, then all
deeper states are disabled as well, but the "disable" variable does not
reflect it. Likewise, if one enables a deep state but a lighter state
still is disabled, then this has no effect. A related section has been
added to the documentation.
Signed-off-by: Carsten Emde <C.Emde@osadl.org>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Diffstat (limited to 'drivers/nubus/proc.c')
0 files changed, 0 insertions, 0 deletions