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From: John Baldwin <jhb@freebsd.org>
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Subject: Re: ixgb TSO performance degrades by ~30% between 7.4 and 8.2/9.0/9.1
Date: Wed, 24 Oct 2012 11:07:10 -0400
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 (bigwig.baldwin.cx); Wed, 24 Oct 2012 11:07:26 -0400 (EDT)
Cc: Garrett Cooper <yanegomi@gmail.com>, Jack F Vogel <jfv@freebsd.org>
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On Tuesday, October 23, 2012 6:57:01 pm Garrett Cooper wrote:
> Hi,
> 
> Doing some poking around at the ixgb driver with a card I have at
> $work using netperf and two machines hooked up over crossover, I
> discovered that while ixgb's throughput performance was fantastic on
> 7.3/7.4, thoughput performance of the card is degraded on 8.2/9.0/9.1
> by ~30% (9400Mbps on 7.4 -> 6294Mbps on 9.0 for example). LRO
> performance on the other hand is fantastic and doesn't degrade with
> the card across FreeBSD versions. Performance remains constant with
> ixgb across 8.2/9.0/9.1. I didn't observe the CPU usage.

Interesting, maybe as an experiment try hacking the #ifdef's to use
if_start() instead of if_transmit().

-- 
John Baldwin