Re: [PATCH 3/3]cpuidle take2: Basic documentation for cpuidle
From: Pavel Machek <hidden>
Date: 2007-02-27 09:40:01
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Hi!
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Documentation for cpuidle infrastructure Signed-off-by: Venkatesh Pallipadi <redacted> Signed-off-by: Adam Belay <redacted> Signed-off-by: Shaohua Li <redacted> Index: linux-2.6.21-rc-mm/Documentation/cpuidle/core.txt ===================================================================--- /dev/null +++ linux-2.6.21-rc-mm/Documentation/cpuidle/core.txt@@ -0,0 +1,17 @@ + + Supporting multiple CPU idle levels in kernel + + cpuidle + +General Information: + +Various CPUs today support multiple idle levels that are differentiated +by varying exit latencies and power consumption during idle. +cpuidle is a generic in-kernel infrastructure that separates +idle policy (governor) from idle mechanism (driver) and provides a +standardized infrastructure to support independent development of +governors and drivers. + +cpuidle resides under /drivers/cpuidle.
Drop leading slash? Merge this to some other docs, since it is so short?
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Index: linux-2.6.21-rc-mm/Documentation/cpuidle/driver.txt ===================================================================--- /dev/null +++ linux-2.6.21-rc-mm/Documentation/cpuidle/driver.txt@@ -0,0 +1,24 @@ + + + Supporting multiple CPU idle levels in kernel + + cpuidle drivers + + + + +cpuidle driver supports capability detection for a particular system. The +init and exit routines will be called for each online CPU, with a percpu +cpuidle_driver object and driver should fill in cpuidle_states inside +cpuidle_driver depending on the CPU capability.
Huh, perhaps it would be nice to explain what the driver does? Now we know that it does...
+Driver can handle dynamic state changes (like battery<->AC), by calling +force_redetect interface. + +It is possible to have more than one driver registered at the same time and +user can switch between drivers using /sysfs interface. + +Interfaces: +int cpuidle_register_driver(struct cpuidle_driver *drv); +void cpuidle_unregister_driver(struct cpuidle_driver *drv); +int cpuidle_force_redetect(struct cpuidle_device *dev);
register, unregister and redetect... but that somehow does not seem complete?
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Index: linux-2.6.21-rc-mm/Documentation/cpuidle/sysfs.txt ===================================================================--- /dev/null +++ linux-2.6.21-rc-mm/Documentation/cpuidle/sysfs.txt@@ -0,0 +1,27 @@ + + + Supporting multiple CPU idle levels in kernel + + cpuidle sysfs + +System global cpuidle information are under +/sys/devices/system/cpu/cpuidle
"information is"? (Not 100% sure).
+Under this percpu directory, there is a directory for each idle state supported +by the driver, which in turn has +* latency +* power +* time +* usage
This should say... latency (in microseconds), power (in miliwats), and explain what time (which units?) and usage means. (Total time spent in that state, usage == number of enters into that state?)
+ Supporting multiple CPU idle levels in kernel + + cpuidle governors + + +cpuidle governor is policy routine that decides what idle state to enter at +any given time. cpuidle core uses different callbacks to governor while +handling idle entry. +* select_state callback where governor can determine next idle state to enter +* prepare_idle callback is called before entering an idle state +* scan callback is called after a driver forces redetection of the states
Can we get some visual separation between functions and their descriptions? scan() callback? scan -- callback?
+More than one governor can be registered at the same time and +user can switch between drivers using /sysfs interface.
<describe interface here>? Explain why we want more than one governor? Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html