linux-kernel - Re: [PATCH] i386 add idle notifier

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Message-Id: <20061129130944.82e3d9bb.akpm@osdl.org>
Date:	Wed, 29 Nov 2006 13:09:44 -0800
From:	Andrew Morton <akpm@...l.org>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	Stephane Eranian <eranian@....hp.com>,
	linux-kernel@...r.kernel.org, ak@...e.de
Subject: Re: [PATCH] i386 add idle notifier

On Wed, 29 Nov 2006 17:09:39 +0000
Christoph Hellwig <hch@...radead.org> wrote:

> On Wed, Nov 29, 2006 at 08:25:40AM -0800, Stephane Eranian wrote:
> > Hello,
> > 
> > Here is a patch that adds an idle notifier to the i386 tree.
> > The idle notifier functionalities and implementation are
> > identical to the x86_64 idle notifier. We use the idle notifier
> > in the context of perfmon.
> > 
> > The patch is against Andi Kleen's x86_64-2.6.19-rc6-061128-1.bz2
> > kernel. It may apply to other kernels but it needs some updates
> > to poll_idle() and default_idle() to work correctly.
> 
> Walking through a notifier chain on every single interrupt (including
> timer interrupts) seems rather costly.  What do you need this for
> exactly?

yes, it's a worry.

Why doesn't enter_idle() do the test_and_set_bit() thing, like
exit_idle()?
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