[lkml]   [2008]   [Nov]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [Bug #11308] tbench regression on each kernel release from 2.6.22 -> 2.6.28
From: Linus Torvalds <>
Date: Mon, 17 Nov 2008 12:30:00 -0800 (PST)

> On Mon, 17 Nov 2008, David Miller wrote:
> >
> > It's on my workstation which is a much simpler 2 processor
> > UltraSPARC-IIIi (1.5Ghz) system.
> Ok. It could easily be something like a cache footprint issue. And while I
> don't know my sparc cpu's very well, I think the Ultrasparc-IIIi is super-
> scalar but does no out-of-order and speculation, no?

I does only very simple speculation, but you're description is accurate.

> So I could easily see that the indirect branches in the scheduler
> hurt much more, and might explain why the x86 profile looks so
> different.


> One thing that non-NMI profiles also tend to show is "clumping", which in
> turn tends to rather excessively pinpoint code sequences that release the
> irq flag - just because those points show up in profiles, rather than
> being a spread-out-mush. So it's possible that Ingo's profile did show the
> scheduler more, but it was in the form of much more spread out "noise"
> rather than the single spike you saw.


 \ /
  Last update: 2008-11-17 22:01    [W:0.191 / U:2.364 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site