Date: Fri, 18 Oct 2002 11:13:54 -0700 (PDT) From: Kelly Yancey <kbyanc@posi.net> To: Luigi Rizzo <rizzo@icir.org> Cc: Petri Helenius <pete@he.iki.fi>, Lars Eggert <larse@ISI.EDU>, <freebsd-net@FreeBSD.ORG> Subject: Re: ENOBUFS Message-ID: <20021018110238.T1611-100000@gateway.posi.net> In-Reply-To: <20021018105922.E82982@carp.icir.org>
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On Fri, 18 Oct 2002, Luigi Rizzo wrote:
> How is the measurement done, does the box under test act as a router
> with the smartbit pushing traffic in and expecting it back ?
>
The box has 2 interfaces, a fxp and a em (or bge). The GigE interface is
configured with 7 VLANs. THe SmartBit produces X byte UDP datagrams that go
through a Foundry ServerIron switch for VLAN tagging and then to the GigE
interface (where they are untagged). The box is acting as a router and all
traffic is directed out the fxp interface where it returns to the SmartBit.
> The numbers are strange, anyways.
>
> A frame of N bytes takes (N*8+160) nanoseconds on the wire, which
> for 330-byte frames should amount to 1000000/(330*8+160) ~= 357kpps,
> not the 249 or so you are seeing. Looks as if the times were 40% off.
>
Yeah, I've never made to much sense of the actual numbers myself. Our
resident SmartBit expert runs the tests and provides me with the results. I
use them more for getting an idea of the relative performance of one
configuration over another and not as absolute numbers themselves. I'll check
with our resident expert and see if he can explain how it calculates those
numbers. The point being, though, that there is an undeniable drop-off with
332 byte or smaller packets. We have never seen any such drop-off using the
bge driver.
Thanks,
Kelly
> cheers
> luigi
>
> On Fri, Oct 18, 2002 at 10:45:13AM -0700, Kelly Yancey wrote:
> ...
> > > can push out over 400kpps (64byte frames) on a 2.4GHz box.
> > >
> > > luigi
> > >
> >
> > Using a SmartBit to push traffic across a 1.8Ghz P4; 82543 chipset card
> > plugged into PCI-X bus:
> >
> > FrameSize TxFrames RxFrames LostFrames Lost (%)
> > 330 249984 129518 120466 48.19
> > 331 249144 127726 121418 48.73
> > 332 248472 140817 107655 43.33
> > 333 247800 247800 0 0
> >
> > It has no trouble handling frames 333 bytes or larger. But for any frame
> > 332 bytes or smaller we consistently see ~50% packet loss. This same machine
> > easily pushes ~100Mps with the very same frame sizes using a bge card rather
> > than em.
> >
> > I've gotten the same results with both em driver version 1.3.14 and 1.3.15
> > on both FreeBSD 4.5 and 4.7 (all 4 combinations, that is).
> >
> > Kelly
> >
> > --
> > Kelly Yancey -- kbyanc@{posi.net,FreeBSD.org}
> > FreeBSD, The Power To Serve: http://www.freebsd.org/
> >
> >
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--
Kelly Yancey -- kbyanc@{posi.net,FreeBSD.org}
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