From mboxrd@z Thu Jan 1 00:00:00 1970 From: P@draigBrady.com Subject: Re: Xeon smp performance Date: Mon, 08 Mar 2004 15:15:30 +0000 Sender: netdev-bounce@oss.sgi.com Message-ID: <404C8E12.4060403@draigBrady.com> References: <20040308132354.77437.qmail@web21101.mail.yahoo.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: quoted-printable Cc: netdev@oss.sgi.com Return-path: To: satya srikanth In-Reply-To: <20040308132354.77437.qmail@web21101.mail.yahoo.com> Errors-to: netdev-bounce@oss.sgi.com List-Id: netdev.vger.kernel.org satya srikanth wrote: > Hi, > I am writing a simple sniffer program that will > sniff packets in a gigabit network. I am using a dual > processor 2 GHz Xeon processor with one Intel Pro-1000 > desktop adapter, running 2.4.20-8smp linux.=20 > I found that for all packet sizes and network > bandwidth, 2.4.20-8 uniprocessor version that uses > only one processor is performing better than > 2.4.20-8smp using two processors in terms of packet > drops and CPU utilization. Each processor in smp is > utilizing more CPU than one processor in uni-processor > case. What is the reason for this peculiar behaviour? > Is it possible for me to use the power of second > processor without adding more NICs. Will I face > similar problems with 2.6 also? Anybody familiar with > these please help me out. That matches my experience. My chipset was Intel E7501 with 2 intel pro-1000 adapters. I used the base 2.4.20 kernel with latest intel drivers. I had 2 processes capturing packets and noticed that 2 CPUs is 7% slower than one CPU. Note I was using a non SMP kernel for the one CPU case. I'm going to have to look into improving this soon. First I'm going to look at IRQ and process affinity. P=E1draig.