Date: Thu, 19 Jun 1997 11:07:59 +0200 From: sthaug@nethelp.no To: tom@sdf.com Cc: ccsanady@scl.ameslab.gov, hackers@FreeBSD.ORG, matt@3am-software.com Subject: Re: Network concurrency problems!? Message-ID: <7618.866711279@verdi.nethelp.no> In-Reply-To: Your message of "Wed, 18 Jun 1997 18:16:49 -0700 (PDT)" References: <Pine.BSF.3.95q.970618181004.11965A-100000@misery.sdf.com>
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> 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
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