Messages in this thread | | | Date | Mon, 17 Nov 2008 12:30:00 -0800 (PST) | From | Linus Torvalds <> | Subject | Re: [Bug #11308] tbench regression on each kernel release from 2.6.22 -> 2.6.28 |
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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? 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.
Linus
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