Re: [RFC V1] cpuidle: add idle routine registration and cleanup pm_idlepointer

[Arjan van de Ven]

 On 10/20/2010 12:47 PM, Venkatesh Pallipadi wrote:
> On Wed, Oct 20, 2010 at 12:44 PM, Arjan van de Ven
> <arjan@xxxxxxxxxxxxxxx>  wrote:
> >   On 10/20/2010 12:40 PM, Vaid
> > > > you ALWAYS have at least 2 idle handling states. The platform idle
> > > > one and the generic busy waiting one.
> > > > the later is needed for "I want absolutely 0 latency" cases.
> > > Some special overrides like idle=poll should handle this case even if
> > > cpuidle and related registration mechanism is compiled out. The point
> > > is that we need some flexibility even if the full framework is not
> > > included.
> > this is not idle=poll
> >
> > this is an (privileged) app or driver, at runtime, requesting a 0 usec max
> > latency for a short or long period of time.
> >
> >
> > > > > Making current cpuidle as default in kernel
> > > > not "in the kernel" but "for x86".
> > > > You're solving an x86 problem here, right?
> > > > (the pm_idle is an x86 only problem. other architectures should be
> > > > able to keep doing what they are doing)
> > > > For x86, lets solve it by going to cpuidle period... and if Andi can
> > > > find some bloat in cpuidle, lets see if the fat can be trimmed.
> > > Ok, you are suggesting that for x86 lets move cpuidle in kernel
> > > always, while it can be an optional module for other archs as it
> > > stands today.  We can slim down the cpuidle from current 7K or atleast
> > > split some parts like governors as modules if needed.
> > governors as modules is a total pain. modules don't solve the problem.
> > really. it's still code you need.
> > we have two governors today, menu and ladder
> > menu is best on anything that is tickless
> > ladder is useless on any tickless kernel, and likely not better than menu on
> > non-tickless.
> > that's it.
> > It will be good to have other archs also follow the same cpuidle
> I don't think they have to be modules. There can be a CPUIDLE_LITE
> which deCONFIG entire governor.c and individual governors (and
> probably sysfs stuff as well) for archs that can only use one state at
> any time, but still want to do config or runtime detection of one
> state and register that state.

there is no such case though; you always have at least 2 options!
(the hardware equivalent of "hlt" and the polling option)
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