Date: Fri, 25 Mar 2005 08:00:58 -0800 From: "David G. Lawrence" <dg@dglawrence.com> To: David Malone <dwmalone@maths.tcd.ie> Cc: freebsd-bugs@freebsd.org Subject: Re: broken bandwidth-delay product window limiting Message-ID: <20050325160058.GD905@opteron.dglawrence.com> In-Reply-To: <20050325153558.GA22521@walton.maths.tcd.ie> References: <20050325152910.GC905@opteron.dglawrence.com> <20050325153558.GA22521@walton.maths.tcd.ie>
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> On Fri, Mar 25, 2005 at 07:29:10AM -0800, David G. Lawrence wrote: > > The "bandwidth-delay product window limiting" code in 5.x appears to be > > quite broken. In my tests here, the window is hard limited to 2 segments, > > regardless of the actual bandwidth-delay product, and this results in very > > poor performance over non-local TCP connections. I'd suggest shipping 5.4 > > and future releases with net.inet.tcp.inflight.enable=0 until this problem > > can be fixed. > > Have you seen: > > http://www.FreeBSD.org/cgi/query-pr.cgi?pr=75122 I have now. :-) I saw parts of the discussion when it was occuring, but didn't really put it all together. > I wonder if it is the same bug or a different one? You know, it's really hard to tell. This code is very complicated. All I've been able to determine is that many tests with a variety of non-local, but 100-1000Mbps connected machines, all resulted in a 2 segment limit on the TCP window with top performance of less than 1.5Mbps. With the old not-so-clever algorithm (inflight.enable=0), I see about 15 times this with sendspace=64K. -DG David G. Lawrence President Download Technologies, Inc. - http://www.downloadtech.com - (866) 399 8500 TeraSolutions, Inc. - http://www.terasolutions.com - (888) 346 7175 The FreeBSD Project - http://www.freebsd.org Pave the road of life with opportunities.
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