From mboxrd@z Thu Jan 1 00:00:00 1970 From: Simon Oliver Subject: Process binding on Dual P4 Xeon Date: Tue, 23 Jul 2002 14:19:14 +0100 Sender: linux-smp-owner@vger.kernel.org Message-ID: <3D3D57D2.776C6482@umist.ac.uk> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: List-Id: Content-Type: text/plain; charset="us-ascii" To: SuSE Linux List , linux-smp@vger.kernel.org I have recently installed a new dual P4 Xeon system. For a particularly computeintensive program I have been advised to turn of hyperthreading in the BIOS, so now Linux sees two CPUs instead of four logical CPUs - makes sense :-) I know that the binding of a process to a cpu is "loose" under linux (as apposed to Irix say) and one expects jobs to hop between CPUs every now and then. But I have been monitoring (via top) a simple perl script (no forks or threading involved) and not only does it switch CPU, sometimes it seems to split accross the CPUs with 50% utilization on each CPU, or even a 25/75 split. I have never noticed this before on dual CPU machines (I have a few dual PIIIs). The machine is still running the SuSE supplied SMP kernel: Linux version 2.4.18-64GB-SMP (root@SMP_X86.suse.de) (gcc version 2.95.3 20010315 (SuSE)) #1 SMP Wed Mar 27 13:58:12 UTC 2002 Please enlighten me. -- Simon Oliver