Date: Tue, 26 Dec 1995 11:51:02 +0200 From: Petri Helenius <pete@sms.fi> To: davidg@Root.COM Cc: questions@freebsd.org, wollman@freebsd.org, olah@freebsd.org Subject: Re: Unpleasant scrolling behaviour on 2.1.0 (fwd) Message-ID: <199512260951.LAA27322@silver.sms.fi> In-Reply-To: <199512260920.BAA06348@corbin.Root.COM> References: <199512260801.KAA27158@silver.sms.fi> <199512260920.BAA06348@corbin.Root.COM>
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David Greenman writes: > > I did, that's why I know it isn't 16k. "you'll soon figure this out" doesn't > score any positive points for your assertions. > I get (running my 2.1) win size of around 17k for the lo0 and default win of 16k for the ed1. It seems that some fuzzy logic is applied in the code :-) > > Yes, in general it would be best for the window to be at least twice the > MTU. However, for the loopback device the way the code is written actually > makes this work significantly worse than using a larger MTU. There are a > variety of reasons why this is the case, and some of them are due to bugs in > the code. On first glance, one of the bugs involved here appears to be that > even though TCP_MAXWIN is 64k, the actual window being used (as seen above in > tcpdump) is 28K and the packets sent through the loopback device are 14K > large. This is likely at least partially due to the socket highwater limit on > the xmit and/or receive side being lower than the MTU, but I haven't recently > looked at the code to be sure. Something to try would be to increase SO_RCVBUF > and/or SO_SNDBUF to 64k and see how things are effected. ...or: > > sysctl -w net.inet.tcp.sendspace=65536 > sysctl -w net.inet.tcp.recvspace=65536 > > ...but there are likely other limits or bugs that will get in the way of > making this work as expected. > It's good that we do agree on that something should be done... > >On the helpfulness side, I'd tried to raise discussion on this topic > >a couple of times before, until I threw the flame above, nobody cared. > > The only other message I've seen from you on this subject was worded in > much the same way as this last one: > > "What's your lo0 MTU? If it's the 16384 that some > non-tcp-knowledgeable person put in sometime in the past " > > > If your tone hadn't been so completely condescending, perhaps someone may > have actually listened to you. > Perhaps you're refering to some other messages from a few months back? If > so, they probably got completely overlooked while I was working on the 2.1 > release, and any other people (Garrett, Andras) that might have been > interested don't subscribe to freebsd-questions. That has been the case. I was not aware that the people involved in this issue do not read this list. Maybe I shouldn't either :-) > Merry Christmas. > ...and Happy New Year. > -DG Pete
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