From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Kok, Auke" Subject: Re: questions on NAPI processing latency and dropped network packets Date: Thu, 10 Jan 2008 11:01:30 -0800 Message-ID: <47866B8A.3040607@intel.com> References: <478654C3.60806@nortel.com> <478666F4.50405@hp.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Chris Friesen , netdev@vger.kernel.org, linux-kernel@vger.kernel.org To: Rick Jones Return-path: Received: from mga02.intel.com ([134.134.136.20]:7760 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754671AbYAJTCR (ORCPT ); Thu, 10 Jan 2008 14:02:17 -0500 In-Reply-To: <478666F4.50405@hp.com> Sender: netdev-owner@vger.kernel.org List-ID: Rick Jones wrote: >> 1) Interrupts are being processed on both cpus: >> >> root@base0-0-0-13-0-11-1:/root> cat /proc/interrupts >> CPU0 CPU1 >> 30: 1703756 4530785 U3-MPIC Level eth0 > > IIRC none of the e1000 driven cards are multi-queue the pci-express variants are, but the functionality is almost always disabled (and relatively new anyway). even with multiqueue, you can still have only a single irq line (which defeats the purpose of course mostly). >, so while the above > shows that interrupts from eth0 have been processed on both CPUs at > various points in the past, it doesn't necessarily mean that they are > being processed on both CPUs at the same time right? never will, an irq can only be processed on one cpu at a time anyway, obviously the irq here has been migrated ONCE from one of the cpu's to the other. unfortunately you can't see from /proc/interrupts whether this happens frequently or not, or how many times it happened before. Auke