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Date:      Fri, 18 Oct 2002 17:40:57 -0400
From:      Don Bowman <don@sandvine.com>
To:        "'Kevin_Stevens@pursued-with.net'" <Kevin_Stevens@pursued-with.net>, Don Bowman <don@sandvine.com>
Cc:        freebsd-net@FreeBSD.ORG
Subject:   RE: ENOBUFS
Message-ID:  <FE045D4D9F7AED4CBFF1B3B813C8533701022CD2@mail.sandvine.com>

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From: Kevin Stevens [mailto:Kevin_Stevens@pursued-with.net]
> On Fri, 18 Oct 2002, Don Bowman wrote:
> 
> > > what do you mean ? it works great for me. even on -current i
> > > can push out over 400kpps (64byte frames) on a 2.4GHz box.
> >
> > 400kpps seems like very poor performance.
> > Unless I do the math wrong, this is only ~200Mbps,
> > the nic should be able to allow ~2-3Mpps (GE bidirectional).
> 
> First, you're only pushing packets, so you are only talking a 
> potential 1GB, not two.
> 
> Second, sending minimum-size packets, while a best-case 
> metric for pps, is a worst-case metric for throughput.  
> I don't think that you can conclude that 20% theoretical 
> bandwidth utilization at minimum packet size is poor
> performance; in fact it seems pretty good to me.  

Problem is, I'm making a bridge application which operates in a network
similar to a router, not an endpoint server which receives TCP packets.
There's a huge number of small packets on the internet due to 
TCP ACK's etc.

I need to be able to do ~1.5Mpps x 2 for a single interface (both
directions), which becomes ~1.5Mpps x 4 for an 'in' and an 'out'
interface.

Clearly you are correct that for most client/server applications
64-byte pps are not the interesting stat.

Clearly I will have some tuning ahead, and likely I will not succeed,
but for sure my 1U XEON with 6 gigabit nics will work very hard
for its living :)

--don (don@sandvine.com www.sandvine.com)

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