linux-kernel - Re: [PATCH] add i386 idle notifier (take 3)

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Message-ID: <20061222010641.GK6993@stusta.de>
Date:	Fri, 22 Dec 2006 02:06:41 +0100
From:	Adrian Bunk <bunk@...sta.de>
To:	Stephane Eranian <eranian@....hp.com>
Cc:	Andrew Morton <akpm@...l.org>, linux-kernel@...r.kernel.org,
	ak@...e.de
Subject: Re: [PATCH] add i386 idle notifier (take 3)

On Thu, Dec 21, 2006 at 01:12:42AM -0800, Stephane Eranian wrote:
> Andrew,
> 
> On Wed, Dec 20, 2006 at 09:05:14PM -0800, Andrew Morton wrote:
> > On Wed, 20 Dec 2006 06:05:00 -0800
> > Stephane Eranian <eranian@....hp.com> wrote:
> > 
> > > Hello,
> > > 
> > > Here is the latest version of the idle notifier for i386.
> > > This patch is against 2.6.20-rc1 (GIT). In this kernel, the idle
> > > loop code was modified such that the lowest level idle
> > > routines do not have loops anymore (e.g., poll_idle). As such,
> > > we do not need to call enter_idle() in all the interrupt handlers.
> > > 
> > > This patch also duplicates the x86-64 bug fix for a race condition
> > > as posted by Venkatesh Pallipadi from Intel.
> > > 
> > > changelog:
> > > 	- add idle notification mechanism to i386
> > > 
> > 
> > None of the above text is actually usable as a changelog entry.  We are
> > left wondering:
> > 
> > - why is this patch needed?
> > 
> > - what does it do?
> > 
> > - how does it do it?
> > 
> > The three questions which all changelogs should answer ;)
> 
> Sorry about that. Here is a new changelog:
> 
> changelog:
> 	- add a notifier mechanism to the low level idle loop. You can
> 	  register a callback function which gets invoked on entry and exit
> 	  from the low level idle loop. The low level idle loop is defined as
> 	  the polling loop, low-power call, or the mwait instruction. Interrupts
> 	  processed by the idle thread are not considered part of the low level
> 	  loop. The notifier can be used to measure precisely how much is spent
> 	  in useless execution (or low power mode). The perfmon subsystem uses it
> 	  to turn on/off monitoring.


Why is this patch not submitted as part of the perfmon patch that also 
adds a user of this code?

And why does it bloat the kernel with EXPORT_SYMBOL's although even your 
perfmon-new-base-061204 doesn't seem to add any modular user?


> -Stephane

cu
Adrian

-- 

       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed

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