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

Linus Torvalds
2008-11-17T19:48:33Z

On Mon, 17 Nov 2008, David Miller wrote:

> From: Ingo Molnar <mingo-X9Un+BFzKDI@public.gmane.org>
> Date: Mon, 17 Nov 2008 12:01:19 +0100
>
> > The scheduler's overhead barely even registers on a 16-way x86 system
> > i'm running tbench on. Here's the NMI profile during 64 threads tbench
> > on a 16-way x86 box with an v2.6.28-rc5 kernel [config attached]:
>
> Try a non-NMI profile.
>
> It's the whole of the try_to_wake_up() path that's the problem.

David, that makes no sense. A NMI profile is going to be a _lot_ more
accurate than a non-NMI one. Asking somebody to do a clearly inferior
profile to get "better numbers" is insane.

We've asked _you_ to do NMI profiling, it shouldn't be the other way
around.

Linus