Date: Thu, 31 Oct 2002 19:01:30 -0800 From: Bakul Shah <bakul@bitblocks.com> To: Fran.Lawas-Grodek@grc.nasa.gov, Cindy.Tran@grc.nasa.gov Cc: freebsd-net@FreeBSD.ORG, Mark.Allman@grc.nasa.gov Subject: Re: Problem in High Speed and Long Delay with FreeBSD Message-ID: <200211010301.WAA03036@thunderer.cnchost.com> In-Reply-To: Your message of "Thu, 31 Oct 2002 13:56:01 EST." <20021031135601.B23802@grc.nasa.gov>
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> Testing commands used: > receiver> ttcp -b 312500 -l 1024 -r -s > sender> ttcp -b 312500 -l 1024 -n 100000 -s -t receiverhost Pure speculation: Since you are writing 1K at a time, could it be an N^2 effect while appending mbufs? Since you can have many MBs in the pipe due to large delay*BW, you can potentially have many many mbufs. The Nth write will have to traverse O(N) mbuf chains to append the new data. One way to test is to increase the -l parameter value to something large and see if the throughput improves. If this is the case, FreeBSD will have to optimize this common case for stream protocols. Note that I haven't even looked at the relevant FreeBSD code! For all I know it may already be doing this. -- bakul To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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