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Date: Mon, 17 Nov 2008 12:30:00 -0800 (PST) From: Linus Torvalds <torvalds@...ux-foundation.org> To: David Miller <davem@...emloft.net> cc: mingo@...e.hu, dada1@...mosbay.com, rjw@...k.pl, linux-kernel@...r.kernel.org, kernel-testers@...r.kernel.org, cl@...ux-foundation.org, efault@....de, a.p.zijlstra@...llo.nl, shemminger@...tta.com Subject: Re: [Bug #11308] tbench regression on each kernel release from 2.6.22 -> 2.6.28 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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