From mboxrd@z Thu Jan 1 00:00:00 1970 From: Linus Torvalds Subject: Re: [Bug #11308] tbench regression on each kernel release from 2.6.22 -> 2.6.28 Date: Mon, 17 Nov 2008 12:30:00 -0800 (PST) Message-ID: References: <20081117184951.GA5585@elte.hu> <20081117.113936.81699150.davem@davemloft.net> <20081117.121641.167690467.davem@davemloft.net> Mime-Version: 1.0 Return-path: In-Reply-To: <20081117.121641.167690467.davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org> Sender: kernel-testers-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: TEXT/PLAIN; charset="us-ascii" Content-Transfer-Encoding: 7bit To: David Miller Cc: mingo-X9Un+BFzKDI@public.gmane.org, dada1-fPLkHRcR87vqlBn2x/YWAg@public.gmane.org, rjw-KKrjLPT3xs0@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, kernel-testers-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, cl-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, efault-Mmb7MZpHnFY@public.gmane.org, a.p.zijlstra-/NLkJaSkS4VmR6Xm/wNWPw@public.gmane.org, shemminger-ZtmgI6mnKB3QT0dZR+AlfA@public.gmane.org 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