Date: 22 Aug 1998 19:49:39 GMT From: freebsd-net-list@salford.ac.uk To: freebsd-net@FreeBSD.ORG Subject: Re: 2.2.6 net performance and panic with 1000's of sockets open Message-ID: <19980822195713.11147.qmail@ananke.salford.ac.uk>
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Mark Powell (mark@nospam.salford.ac.uk) wrote: : In article <6pl4lk$a51$3@ocean.cup.hp.com>, Rick Jones <foo@bar.baz> wrote: : >I think Steinar meant ttcp the benchmark, not T/TCP the TCP protocol : >extensions. As for netperf only getting 64 Mbit/s, it would help if : >you could do a cut and paste of your command lines so we can see the Of course, I was silly and failed to ask for the netperf client output. : If I use: : $ route -n change <server> -recvpipe 65536 -sendpipe 65536 Did the socket buffer size reports change in the netperf output when you did that route command? : On the client, I've seen 73Mbit/s. : If I do a UDP_STREAM I get 95.8Mbit/s. One has to be *very* careful with the UDP_STREAM test and really only report the recevie rate. There are some systems and/or drivers out there which do not report ENOBUFs when the transmit queues overflow. [you may have actually reported the receive rate, I am just paranoid when it comes to the UDP_STREAM test...I very nearly did not include it in netperf ] If you were indeed getting 95 Mbit/s with UDP_STREAM, it is possible that the window size, even at 65535 bytes was not enought to deal with the latency of the connection. One first-order appoximation of the limit of performance with TCP is W/RTT where W is the window size, and RTT is the round-trip time. Some NICs have higher latency than others...there have been some NICs with really bad latency, which is one reason why there is a TCP_RR test in netperf. If there is high latency (high is a relative term) increasing the window can help. It is also a good idea to check the netstat stats for retransmitted segments. The occasional loss of a datagram will not show-up in the UDP_STREAM results, but it can in a TCP_STREAM test. rick jones -- these opinions are mine, all mine; HP might not want them anyway... :) feel free to email, or post, but please do not do both... my email address is raj in the cup.hp.com domain... To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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