linux-kernel - Re: [v8 PATCH 2/8]: cpuidle: implement a list based approach to register a set of idle routines.

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Date:	Wed, 14 Oct 2009 11:47:27 +0530
From:	Arun R Bharadwaj <arun@...ux.vnet.ibm.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Ingo Molnar <mingo@...e.hu>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	Dipankar Sarma <dipankar@...ibm.com>,
	Balbir Singh <balbir@...ibm.com>,
	Arjan van de Ven <arjan@...radead.org>,
	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	linux-arch@...r.kernel.org, linux-acpi@...r.kernel.org,
	Arun Bharadwaj <arun@...ux.vnet.ibm.com>
Subject: Re: [v8 PATCH 2/8]: cpuidle: implement a list based approach to
	register a set of idle routines.

* Andi Kleen <andi@...stfloor.org> [2009-10-12 20:00:05]:

> Peter Zijlstra <a.p.zijlstra@...llo.nl> writes:
> >
> > So does it make sense to have a set of sets?
> >
> > Why not integrate them all into one set to be ruled by this governor
> > thing?
> 
> cpuidle is currently optional, that is why the two level hierarchy
> is there so that you can still have simple idle selection without it.
> 
> % size drivers/cpuidle/*.o
>    text    data     bss     dec     hex filename
>    5514    1416      44    6974    1b3e drivers/cpuidle/built-in.o
> 
> Adding it unconditionally would add ~7k to everyone who wants idle functions.
> 
> I think making it unconditional would require putting it on a serious
> diet first.
> 

Hi Andi,

Yes, this is a valid point.

How about something like this..
If the arch does not enable CONFIG_CPU_IDLE, the cpuidle_idle_call
which is called from cpu_idle() should call default_idle without
involving the registering cpuidle steps. This should prevent bloating
up of the kernel for archs which dont want to use cpuidle.

--arun
> -Andi
> -- 
> ak@...ux.intel.com -- Speaking for myself only.
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