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

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Message-ID: <810586B7581CC8469141DADEBC37191224F773F0@BGSMSX102.gar.corp.intel.com>
Date:	Wed, 6 Mar 2013 10:56:12 +0000
From:	"Mansoor, Illyas" <illyas.mansoor@...el.com>
To:	Ingo Molnar <mingo@...nel.org>,
	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

> -----Original Message-----
> From: Ingo Molnar [mailto:mingo.kernel.org@...il.com] On Behalf Of Ingo
> Molnar
> Sent: Wednesday, March 06, 2013 4:06 PM
> To: Mansoor, Illyas; Peter Zijlstra
> Cc: Linux Kernel; Linux PM; Frederic Weisbecker; Ingo Molnar; X86; Len Brown;
> Thomas Gleixner; Matthew Garrett; Tejun Heo; Paul E. McKenney; Rudramuni,
> Vishwesh M; richard@....at; josh@...htriplett.org; Kumar P, Mahesh; Sil, Dyut
> K; Arjan van de Ven
> 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.
Support for Idle notifiers on 32-bit got broken from commit
90e240142bd31ff10aeda5a280a53153f4eff004
Before that they were getting registered from process_64.c since it was not
guarded using
CONFIG_X86_64 

Commit 90e240142bd31ff10aeda5a280a53153f4eff004 merged x8_64 and x86_32 into
process.c and put
Restriction x86_64 on idle notifier which was correct since the notifier calls
were taken from process_64.c

> 
> 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 ...
Agree, it should not be conflicting each other. 
Is there an alternative to idle notifications once those are deprecated. 
Sorry couldn't find that from Alex Shi's patches on LKML

Thanks,
Illyas

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