From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Subject: Re: [Bug #11308] tbench regression on each kernel release from 2.6.22 -> 2.6.28 Date: Mon, 17 Nov 2008 23:47:51 +0100 Message-ID: <20081117224751.GA19905@elte.hu> References: <20081117110119.GL28786@elte.hu> <4921539B.2000002@cosmosbay.com> <20081117161135.GE12081@elte.hu> <20081117.113158.200497613.davem@davemloft.net> Mime-Version: 1.0 Return-path: Content-Disposition: inline In-Reply-To: <20081117.113158.200497613.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: 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, torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org * David Miller wrote: > From: Ingo Molnar > Date: Mon, 17 Nov 2008 17:11:35 +0100 > > > Ouch, +4% from a oneliner networking change? That's a _huge_ speedup > > compared to the things we were after in scheduler land. > > The scheduler has accounted for at least %10 of the tbench > regressions at this point, what are you talking about? yeah, you are probably right when it comes to task migration policy impact - that can have effects in that range. (and that, you have to accept, is a fundamentally hard and fragile job to get right, as it involves observing the past and predicting the future out of it - at 1.3 million events per second) So above i was just talking about straight scheduling code overhead. (that cannot have been +10% of the total - as the whole scheduler only takes 7% total - TLB flush and FPU restore overhead included. Even the hrtimer bits were about 1% of the total.) Ingo