linux-kernel - Re: [PATCH] x86: fix idle notifier not being called in CONFIG_X86

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Date:	Wed, 6 Mar 2013 11:36:27 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	"Mansoor, Illyas" <illyas.mansoor@...el.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>,
	Linux PM <linux-pm@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>, X86 <x86@...nel.org>,
	Len Brown <lenb@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Matthew Garrett <matthew.garrett@...ula.com>,
	Tejun Heo <tj@...nel.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	"Rudramuni, Vishwesh M" <vishwesh.m.rudramuni@...el.com>,
	"richard@....at" <richard@....at>,
	"josh@...htriplett.org" <josh@...htriplett.org>,
	"Kumar P, Mahesh" <mahesh.kumar.p@...el.com>,
	"Sil, Dyut K" <dyut.k.sil@...el.com>,
	Arjan van de Ven <arjan@...radead.org>
Subject: Re: [PATCH] x86: fix idle notifier not being called in CONFIG_X86_32


* Mansoor, Illyas <illyas.mansoor@...el.com> wrote:

> > * Illyas Mansoor <illyas.mansoor@...el.com> wrote:
> > 
> > > Idle notifier not registered if CONFIG_X86_32 is defined, those
> > > callbacks are empty for X86_32 platform.
> > >
> > > ifdef CONFIG_X86_64
> > >  void enter_idle(void);
> > >  void exit_idle(void);
> > > else
> > > static inline void enter_idle(void) { } static inline void
> > > exit_idle(void) { } static inline void __exit_idle(void) { } endif
> > >
> > > Make this work on X86_32 platforms by
> > > removing the restriction for X86_64
> > 
> > What will they be used for?
> 
> It's being used by interactive governor, and since the idle notifications are not 
> received It breaks the governor functionality on X86_32

But we never allowed idle notifiers on 32-bit and wanted to phase them out even on 
x86-64 as well.

There's ongoing work to improve power saving in the scheduler - see Alex Shi's 
patchset on lkml: I think the two pieces of code should cooperate within the 
scheduler instead of going in two directions, duplicating effort and getting in each 
other's way ...

Thanks,

	Ingo
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