From owner-freebsd-hackers Thu Jun 19 02:08:14 1997 Return-Path: Received: (from root@localhost) by hub.freebsd.org (8.8.5/8.8.5) id CAA17887 for hackers-outgoing; Thu, 19 Jun 1997 02:08:14 -0700 (PDT) Received: from verdi.nethelp.no (verdi.nethelp.no [195.1.171.130]) by hub.freebsd.org (8.8.5/8.8.5) with SMTP id CAA17882 for ; Thu, 19 Jun 1997 02:08:09 -0700 (PDT) From: sthaug@nethelp.no Received: (qmail 7620 invoked by uid 1001); 19 Jun 1997 09:07:59 +0000 (GMT) To: tom@sdf.com Cc: ccsanady@scl.ameslab.gov, hackers@FreeBSD.ORG, matt@3am-software.com Subject: Re: Network concurrency problems!? In-Reply-To: Your message of "Wed, 18 Jun 1997 18:16:49 -0700 (PDT)" References: X-Mailer: Mew version 1.05+ on Emacs 19.28.2 Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Date: Thu, 19 Jun 1997 11:07:59 +0200 Message-ID: <7618.866711279@verdi.nethelp.no> Sender: owner-hackers@FreeBSD.ORG X-Loop: FreeBSD.org Precedence: bulk > Would a TCP socket have more system overhead than a file on a UFS > filesystem? I guess you can tess this by running dd on a mfs, and > tcpblast/netpipe/ttcp on loopback? Somehow I think the socket would be > faster. I don't know enough about the file system to say whether this is a relevant comparison on one host. It's not a very good comparison to the Ethernet case for the simple reason that the Ethernet MTU is 1500, while the default loopback MTU is 16384. I did a couple of quick tests here on a PPro-200. With the default loopback MTU, I consistently got around 44 MByte/s (M=1048576) using ttcp. With a 1500 byte MTU, I'm down to 27 Mbyte/s - a significant difference. Using the loopback interface the packet needs to traverse both down and up the protocol stack on the same host, so this would tend to decrease performance. I don't know whether the increased performance from a large loopback MTU offsets the decreased performance from traversing the protocol stack twice. Steinar Haug, Nethelp consulting, sthaug@nethelp.no