Re: [Bug #11308] tbench regression on each kernel release from 2.6.22 -> 2.6.28

Ingo Molnar
2008-11-17T22:47:51Z

* David Miller <davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org> wrote:

> From: Ingo Molnar <mingo-X9Un+BFzKDI@public.gmane.org>
> 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