linux-kernel - Re: Scheduler regression: Too frequent timer interrupts(?)

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Message-Id: <1240953796.7620.160.camel@twins>
Date:	Tue, 28 Apr 2009 23:23:16 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Pavel Machek <pavel@....cz>, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org
Subject: Re: Scheduler regression: Too frequent timer interrupts(?)

On Tue, 2009-04-28 at 17:02 -0400, Christoph Lameter wrote:
> On Thu, 23 Apr 2009, Pavel Machek wrote:
> 
> > I'd say that taking interrupt and returning in below 1000nsec is
> > impossible, even on very fast hw.
> 
> Hmmm.... Could it be that CONFIG_NO_HZ caused the timer interrupt to be
> avoided in earlier releases? NO_HZ theory at least is to only schedule
> interrupts when  necessary. So an interrupt is needed at the end of the
> scheduling intervals and not at HZ frequency.

No, NOHZ only works on idle cpus.
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