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SubjectRe: [v11 PATCH 1/9]: cpuidle: Design documentation patch
* Randy Dunlap <rdunlap@xenotime.net> [2010-02-09 09:00:54]:

> 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.
>

Here, it means between. Will remove the abbreviation since it might be
confusing.

>
> > +
> > +
> > +----------------- -----------------
> > +| | | 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/
>

noted.

thanks
arun

> > +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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