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

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Date:	Fri, 17 Apr 2009 17:35:20 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org
Subject: Re: Scheduler regression: Too frequent timer interrupts(?)

* Christoph Lameter <cl@...ux.com> wrote:

> On Fri, 17 Apr 2009, Peter Zijlstra wrote:
> 
> > And a random 1us cutoff, is well, random.
> 
> Its got to be somewhere.

Sorry, that's not a rational answer that makes any sense.

Peter's point is statistics 101: please show absolute values not an 
event distribution cutoff - how much total time do we spend in the 
kernel in that workload?

Is the overhead 1%? 2%? 0.5%? And how did it change from 2.6.22 
onwards? Did it go up by 0.1%, from 1% to 1.1%? Or did the average 
go down by 0.05%, while increasing the spread of events (thus 
fooling your cutoff)?

These are very simple, very basic, very straightforward questions - 
and no straight answer was forthcoming from you. Are you not 
interested in that answer?

	Ingo
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