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Date:      Fri, 18 Oct 2002 14:04:44 -0700 (PDT)
From:      Kevin Stevens <Kevin_Stevens@pursued-with.net>
To:        Don Bowman <don@sandvine.com>
Cc:        freebsd-net@FreeBSD.ORG
Subject:   RE: ENOBUFS
Message-ID:  <20021018135434.Y40012-100000@babelfish.pursued-with.net>
In-Reply-To: <FE045D4D9F7AED4CBFF1B3B813C8533701022CCA@mail.sandvine.com>

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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.  Extrapolating from those
numbers, if the packets were five times larger (320b), you'd hit
theoretical maximum throughput.  Obviously that won't happen, your pps
numbers will go down as the packet size goes up, but it does indicate you
have some headroom, even without going to jumbo frames if the card pushed
five times fewer pps at 1500 byte frames you'd max out the throughput.

You can't tell very much from a single data point like that, but what you
can infer doesn't seem to me to be bad at all.

KeS


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