Date: Tue, 21 Jun 2005 12:36:18 -0700 From: Luigi Rizzo <rizzo@icir.org> To: Pieter de Boer <pieter@thedarkside.nl> Cc: freebsd-net@freebsd.org Subject: Re: Issues with a Large Fat pipe Network simulation Message-ID: <20050621123618.A75484@xorpc.icir.org> In-Reply-To: <42B8667D.9020504@thedarkside.nl>; from pieter@thedarkside.nl on Tue, Jun 21, 2005 at 09:11:57PM %2B0200 References: <42B722EF.2090203@thedarkside.nl> <20050620135044.B35720@xorpc.icir.org> <42B731CD.1040104@thedarkside.nl> <20050621075247.D63359@xorpc.icir.org> <42B84AC8.7050802@thedarkside.nl> <20050621102954.A66904@xorpc.icir.org> <42B8667D.9020504@thedarkside.nl>
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On Tue, Jun 21, 2005 at 09:11:57PM +0200, Pieter de Boer wrote: > Luigi Rizzo wrote: > > > oh yes one thing... you are using 'via foo0' in your rule, > > which means the packet is intercepted both in the input and > > output path, which causes further contention on the queues. > Well, when using 'ip from client to server recv em0', packets get i said 'in recv em0' - you missed the 'in' keyword. > > I am pretty sure there is some issue there, also related to some > > timing issues and tcp window opening mode (slow start vs. linear) > I went to see if there were any sysctl's I could tune a bit. I found these: > net.inet.ip.intr_queue_maxlen: 50 > net.inet.ip.intr_queue_drops: 382136 > > I don't like drops. So I set intr_queue_maxlen to 400, and -poof-, the whoops... of course, i forgot that one too... which is not much of an issue if you use polling or bridging, that's why i forgot :) > speed went up to around 700mbit/s. Still not as fast as it was with 64KB > send/recv spaces, but it's a huge improvement nonetheless. > > I guess we probably should tune a bit more until we're confident that > the middle-box behaves correctly, before adding things like latency and > packet-loss :) > > Thanks for the advice! If you know other settings to tune on the > dummynetting host, I'd very much like to hear them. I'm pondering about > polling (which means we can't do SMP on the dummynet system, but it's > only pushing packets, so that shouldn't matter too much). At least we > have somewhat more info to work with now :) yes you should definitely enable polling if you can, and forget about smp - it's a router anyways, and multiple processors won't help. cheers luigi
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