Date: Fri, 11 Apr 2003 16:07:43 +0200 From: Borje Josefsson <bj@dc.luth.se> To: Mattias Pantzare <pantzer@ludd.luth.se> Cc: David Gilbert <dgilbert@velocet.ca> Subject: Re: tcp_output starving -- is due to mbuf get delay? Message-ID: <200304111407.h3BE7hKl086838@dc.luth.se> In-Reply-To: Your message of Fri, 11 Apr 2003 15:58:55 %2B0200. <3E96CA1F.4070000@ludd.luth.se>
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On Fri, 11 Apr 2003 15:58:55 +0200 Mattias Pantzare wrote: > Terry Lambert wrote: > > Mattias Pantzare wrote: > > = > >>>The products that Jeffrey Hsu and I and Alfred and Jon Mini > >>>worked on at a previous company had no problems at all on a > >>>1Gbit/S saturating the link, even through a VLAN trunk through > >>>Cisco and one other less intelligent switch (i.e. two switches > >>>and a VLAN trunk). > >> > >>A key factor here is that the testst where on a link with a 20ms > >>round-tip time, and using a singel TCP connection. So the switches > >>where in addition to a few routers on a 10Gbit/s network. > > = > > = > > Sorry, but tis is not a factor. If you think it is, then you > > are running with badly tuned send and receive maximum window > > sizes. > > = > > Latency =3D pool retention time =3D 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 should add that I have tried with MTU 1500 also. Using NetBSD as sender= = works fine (just a little bit higher CPU load). When we tried MTU1500 wit= h = FreeBSD as sender, we got even lower performance. Somebody else in this thread said that he had got full GE speed between = two FreeBSD boxes connected back-to-back. I don't question that, but that= = doesn't prove anything. The problem arises when You are trying to do this= = long-distance and have to handle a large mbuf queue. --B=F6rje
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