From owner-freebsd-hackers@FreeBSD.ORG  Tue Feb 21 19:17:50 2006
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From: Nate Nielsen <nielsen-list@memberwebs.com>
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To: FreeLSD <freelsd@rea.mbslab.kiae.ru>
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Date: Tue, 21 Feb 2006 19:27:22 +0000 (GMT)
Cc: hackers@freebsd.org
Subject: Re: FreeBSD-6 and em interface speed
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FreeLSD wrote:
>   Good day!
>  I've obtained the following strang results with the em Ethernet interface
> speeds on a 6.1-PRERELEASE:
>  Polling on:
>   UDP stream to FreeBSD: 327843.84 Kbit/sec,
>   TCP stream to FreeBSD: 524550.12 Kbit/sec.
>  Polling off:
>   UDP stream to FreeBSD: 740409.38 Kbit/sec,
>   TCP stream to FreeBSD: 794348.44 Kbit/sec.

Probably due to the test tool you're using. Does the tool serialize the
UDP stream (ie: wait for a response for each packet)?

In many cases polling will slow down an individual stream slightly,
while upping the total throughput (hundreds of streams). In addition if
your CPU and bus is fast enough to handle the interrupt rate (well
behaved NICs mitigate interrupts) then polling will slow things down in
most cases.

BTW, this should go on freebsd-net.

Cheers,
Nate