Re: [Bug #11308] tbench regression on each kernel release from2.6.22 -> 2.6.28

[Ingo Molnar]

* David Miller <davem@xxxxxxxxxxxxx> wrote:

> From: Ingo Molnar <mingo@xxxxxxx>
> Date: Mon, 17 Nov 2008 17:11:35 +0100
> 
> > Ouch, +4% from a oneliner networking change? That's a _huge_ speedup 
> > compared to the things we were after in scheduler land.
> 
> The scheduler has accounted for at least %10 of the tbench 
> regressions at this point, what are you talking about?

yeah, you are probably right when it comes to task migration policy 
impact - that can have effects in that range. (and that, you have to 
accept, is a fundamentally hard and fragile job to get right, as it 
involves observing the past and predicting the future out of it - at 
1.3 million events per second)

So above i was just talking about straight scheduling code overhead. 
(that cannot have been +10% of the total - as the whole scheduler only 
takes 7% total - TLB flush and FPU restore overhead included. Even the 
hrtimer bits were about 1% of the total.)

	Ingo
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