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SubjectRe: [v11 PATCH 1/9]: cpuidle: Design documentation patch
On 02/09/10 00:29, Arun R Bharadwaj wrote:
> * Arun R Bharadwaj <arun@linux.vnet.ibm.com> [2010-02-09 13:58:16]:
>
> This patch adds a little information about the redesigned cpuidle
> infrastructure in Documentation/cpuidle/core.txt
>
> Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com>
> ---
> Documentation/cpuidle/core.txt | 35 +++++++++++++++++++++++++++++++++++
> 1 file changed, 35 insertions(+)
>
> Index: linux.trees.git/Documentation/cpuidle/core.txt
> ===================================================================
> --- linux.trees.git.orig/Documentation/cpuidle/core.txt
> +++ linux.trees.git/Documentation/cpuidle/core.txt
> @@ -21,3 +21,38 @@ which can be used to switch governors at
> is meant for developer testing only. In normal usage, kernel picks the
> best governor based on governor ratings.
> SEE ALSO: sysfs.txt in this directory.
> +
> +Design:
> +
> +Cpuidle allows for registration of multiple sets of idle routines.
> +The latest registered set is used by cpuidle governors as the current
> +active set to choose the right idle state. This set is managed as a
> +list and each time the newly registered set is added to the head of the
> +list and made the current active set.
> +
> +An example of how this would work on x86 is shown below.
> +
+----------------- -----------------
+| | | |
+| choose b/w | mwait is chosen | mwait |
+| mwait, poll, |-------------------------------------> |(current active|
+| default, c1e | register to cpuidle | set) |
+| | with mwait as the idle routine | |
+----------------- -----------------

What is "b/w" above? "between"? I've see "btw" used a few times as an
abbreviation for between, but I don't recall ever seeing b/w.
OTOH, I have seen b/w used for bandwidth.


> +
> +
> +----------------- -----------------
> +| | | c1, c2, c3 |
> +| ACPI | register to cpuidle | (current) |
> +| discovery |-------------------------------------> |---------------|
> +| | with c1, c2, c3 | mwait |
> +| | as set of idle routines | |
> +----------------- -----------------
> +
> +With this mechanism, a module can register and unregister its set of
> +idle routines at run time in a clean manner.
> +
> +The main idle routine called inside cpu_idle() of every arch is defined in
> +driver/cpuidle/cpuidle.c which would in turn call the idle routine selected

drivers/

> +by the governor. If the CONFIG_CPU_IDLE is disabled, the arch needs to
> +provide an alternate definition for cpuidle_idle_call().


--
~Randy


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