Date: Fri, 11 Apr 2003 18:24:09 +0200 From: Borje Josefsson <bj@dc.luth.se> To: Terry Lambert <tlambert2@mindspring.com> Cc: David Gilbert <dgilbert@velocet.ca> Subject: Re: tcp_output starving -- is due to mbuf get delay? Message-ID: <200304111624.h3BGO9Kl087165@dc.luth.se> In-Reply-To: Your message of Fri, 11 Apr 2003 09:08:19 PDT. <3E96E873.9CC19544@mindspring.com>
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On Fri, 11 Apr 2003 09:08:19 PDT Terry Lambert wrote: > Mattias Pantzare wrote: > > Terry Lambert wrote: > > > Latency = pool retention time = queue size > > > > Then explain this, FreeBSD to FreeBSD on that link uses all CPU on the > > sender, the reciver is fine, but performance is not. NetBSD to FreeBSD > > fills the link (1 Gbit/s). On the same computers. MTU 4470. Send and > > receive maximum windows where tuned to the same values on NetBSD and > > FreeBSD. > > I rather expect that the number of jumbogram buffers on FreeBSD is > tiny and/or your MTU is not being properly negotiated between the > endpoints, and you are fragging the bejesus out of your packets. Both endpoints have MTU set to 4470, as have all the routers inbetween. "traceroute -n -Q 1 -q 1 -w 1 -f remotehost 4470" and netstat both reports 4470. > A good thing to look at at this point would be: > > o Clean boot of FreeBSD target > o Run NetBSD against it > o Save statistics What type of statistics do You mean? > o Clean boot of FreeBSD target > o Run FreeBSD against it > o Save statistics > o Compare saved statistics of NetBSD vs. FreeBSD > against the target machine > > > And packet loss will affect the performance diffrently if you have a > > large bandwith-latency product. > > You mean "bandwidth delay product". Yes, assuming you have packet > loss. From your description of your setup, packet loss should not > be possible, so we can discount it as a factor. Of cause packet loss is possible on a nationwide network. If I loose a packet on the (expected) 10 second test (with NetBSD), recovering from that drops performance from 900+ to ~550 Mbps. Thos shows very clearly if I run "netstat 1". > You may want to > disable fast restart on the FreeBSD sender. Which OID is that? As a side note, I tried to set tcp.inflight_enable, but that made things much worse. --Börje
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