From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753947AbYKQTtY (ORCPT ); Mon, 17 Nov 2008 14:49:24 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751845AbYKQTtQ (ORCPT ); Mon, 17 Nov 2008 14:49:16 -0500 Received: from smtp1.linux-foundation.org ([140.211.169.13]:59780 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751791AbYKQTtP (ORCPT ); Mon, 17 Nov 2008 14:49:15 -0500 Date: Mon, 17 Nov 2008 11:48:33 -0800 (PST) From: Linus Torvalds To: David Miller cc: mingo@elte.hu, rjw@sisk.pl, linux-kernel@vger.kernel.org, kernel-testers@vger.kernel.org, cl@linux-foundation.org, efault@gmx.de, a.p.zijlstra@chello.nl Subject: Re: [Bug #11308] tbench regression on each kernel release from 2.6.22 -> 2.6.28 In-Reply-To: <20081117.112157.146825192.davem@davemloft.net> Message-ID: References: <20081117090648.GG28786@elte.hu> <20081117.011403.06989342.davem@davemloft.net> <20081117110119.GL28786@elte.hu> <20081117.112157.146825192.davem@davemloft.net> User-Agent: Alpine 2.00 (LFD 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 17 Nov 2008, David Miller wrote: > From: Ingo Molnar > Date: Mon, 17 Nov 2008 12:01:19 +0100 > > > The scheduler's overhead barely even registers on a 16-way x86 system > > i'm running tbench on. Here's the NMI profile during 64 threads tbench > > on a 16-way x86 box with an v2.6.28-rc5 kernel [config attached]: > > Try a non-NMI profile. > > It's the whole of the try_to_wake_up() path that's the problem. David, that makes no sense. A NMI profile is going to be a _lot_ more accurate than a non-NMI one. Asking somebody to do a clearly inferior profile to get "better numbers" is insane. We've asked _you_ to do NMI profiling, it shouldn't be the other way around. Linus 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 11:48:33 -0800 (PST) Message-ID: References: <20081117090648.GG28786@elte.hu> <20081117.011403.06989342.davem@davemloft.net> <20081117110119.GL28786@elte.hu> <20081117.112157.146825192.davem@davemloft.net> Mime-Version: 1.0 Return-path: In-Reply-To: <20081117.112157.146825192.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, 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 On Mon, 17 Nov 2008, David Miller wrote: > From: Ingo Molnar > Date: Mon, 17 Nov 2008 12:01:19 +0100 > > > The scheduler's overhead barely even registers on a 16-way x86 system > > i'm running tbench on. Here's the NMI profile during 64 threads tbench > > on a 16-way x86 box with an v2.6.28-rc5 kernel [config attached]: > > Try a non-NMI profile. > > It's the whole of the try_to_wake_up() path that's the problem. David, that makes no sense. A NMI profile is going to be a _lot_ more accurate than a non-NMI one. Asking somebody to do a clearly inferior profile to get "better numbers" is insane. We've asked _you_ to do NMI profiling, it shouldn't be the other way around. Linus