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

David Miller
2008-11-17T19:52:58Z

From: Linus Torvalds <torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
Date: Mon, 17 Nov 2008 11:48:33 -0800 (PST)

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

I wasn't able to on these systems, so instead I did cycle level
evaluation of the parts that have to run with interrupts disabled.

And as a result I found that wake_up() is now 4 times slower than it
was in 2.6.22, I even analyzed this for every single kernel release
till now.

It could be a sparc specific issue, because the call chain is deeper
and we eat a lot more register window spills onto the stack.