Date: Fri, 9 Nov 2001 14:47:11 -0700 From: Nate Williams <nate@yogotech.com> To: stable@FreeBSD.org Cc: jayanth@FreeBSD.org Subject: TCP NewReno causing wild performance fluctuations Message-ID: <15340.20191.441648.662113@caddis.yogotech.com>
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We've been using FreeBSD boxes as our reference ftp servers at work, and because of the recent security issues, I've went through and updated a number of our public boxes from 3.x -> 4.4. However, we're seeing significant variations in ftp throughput from boxes that are directly connected on the lan segment. If I disable the New Reno code, things go back to normal (ie; no fluctuations). I went through the logfiles, and it turns out there has been one fix to the code that hasn't been merged into stable. Rev1.139 in tcp_input.c has not (yet) been merged into -stable. revision 1.139 date: 2001/08/29 23:54:13; author: jayanth; state: Exp; lines: +3 -1 when newreno is turned on, if dupacks = 1 or dupacks = 2 and new data is acknowledged, reset the dupacks to 0. The problem was spotted when a connection had its send buffer full because the congestion window was only 1 MSS and was not being incremented because dupacks was not reset to 0. Obtained from: Yahoo! I hand-merged this change back onto my box, installed a new kernel, and now in my *very* minor testing things appear to be more normal. My question is should this fix be merged into stable, and would the lack of this bugfix explain my performance results? Unfortunately, I don't haven't gotten any tcpdump outputs to analyze what was going on, but I didn't want this bugfix to slip through the cracks. Nate To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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