From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753065AbYANRhd (ORCPT ); Mon, 14 Jan 2008 12:37:33 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751472AbYANRhZ (ORCPT ); Mon, 14 Jan 2008 12:37:25 -0500 Received: from wx-out-0506.google.com ([66.249.82.227]:1396 "EHLO wx-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751403AbYANRhY (ORCPT ); Mon, 14 Jan 2008 12:37:24 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:mime-version:content-type:content-transfer-encoding:content-disposition; b=gNDiV0sCxJkLbUq/9W7Khx8VyGut8o0IFc/4362IC1UsS494UTqLxh2CVJ/KuJw7dAdgHb4BXzZi7c3dpAkPOV/kNw6jVCfNDRpAVaLdo8ytaz0BdW7yXumwZiCl7fyCS3kcj+VNyhfAqSYPiguYwpRUnf+bytokiFHCMA7tC98= Message-ID: Date: Mon, 14 Jan 2008 17:37:21 +0000 From: "Colin Fowler" To: linux-kernel@vger.kernel.org Subject: Performance loss 2.6.22->22.6.23->2.6.24-rc7 on CPU intensive benchmark on 8 Core Xeon MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Please CC me as I'm not subscribed. I have (what is to me) a strange and very repeatable slowdown for a CPU intensive benchmark on my system on newer kernels. Hardware : Dell Precision 470. CPU 2x2.0GHz Quad Core Xeon E5335 CPUs Memory 4GB ECC RAM. OS Ubuntu x86_64 7.10 (Gutsy Gibbon) Compiler : gcc version 4.1.3 20070929 (prerelease) (Ubuntu 4.1.2-16ubuntu2) Benchmark : A ray-trace is performed on 500 times on 17 separate scenes. Workload is distributed by tiling the framebuffer into N 32x32 pixel tiles. Each CPU grabs one of N tiles out of the queue and repeats until no jobs are left. Rendering is to a shared framebuffer (obviously this causes problems with caching). Locking and synchronization is done using pthreads. Other details: The system is cleanly booted for each run. No I/O is performed during the timed portions of the test. The benchmark does however read a model file from the drive and build a data structure from it before each timed portion. On the 2.6.22 series of kernels results are pretty much the same. On 2.6.23 series kernels I see a loss in speed of ~2% across the board. On 2.6.24-rc7 that loss in speed is perhaps very slightly worse (~3%). 2.6.22 Kernels tested: 22.9(Ubuntu Stock Kernel), 22.14, 22.15 2.6.23 Kernels tested: 23.1, 23.3, 23.13 2.6.24 Kernels tested: 24-rc7 I have my kernel compiled to use the SLAB allocator. All other tweaking options are set as defaults. My config files are available at http://vangogh.cs.tcd.ie/fowler/configs . Perhaps I'm configuring something wrong for the type of work I do? regards, Colin