Messages in this thread | | | Date | Fri, 20 Jul 2012 00:22:30 +0200 | From | Carsten Emde <> | Subject | Re: [PATCH 1/1 v3] Honor state disabling in the cpuidle ladder governor |
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On 07/19/2012 11:48 PM, Rafael J. Wysocki wrote: > On Thursday, July 19, 2012, Carsten Emde wrote: >> 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> > > This looks fine to me, but it's too late for v3.6. I can queue it up > for v3.7, though. Yes, please.
Thanks, -Carsten.
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