em0 performance subpar

[Adam Vande More]

On Thu, Apr 28, 2011 at 2:29 AM, Adam Stylinski <kungfujesus06 at gmail.com>wrote:

> Hello,
>
> I have an intel gigabit network adapter (the 1000 GT w/chipset 82541PI)
> which performs poorly in Freebsd compared to the same card in Linux.  I've
> tried this card in two different freebsd boxes and for whatever reason I get
> poor transmit performance.  I've done all of the tweaking specified in just
> about every guide out there (the usual TCP window scaling, larger
> nmbclusters, delayed acks, etc) and still I get only around 600mbps.  I'm
> using jumbo frames, with an MTU of 9000.  I'm testing this with iperf.
>  While I realize that this may not be the most realistic test, linux hosts
> with the same card can achieve 995Mbit/s to another host running this.  When
> the Freebsd box is the server, Linux hosts can transmit to it at around 800
> something Mbit/s.  I've increased the transmit descriptors as specified in
> the if_em man page, and while that gave me 20 or 30 more mbit/s, my transmit
> performance is still below normal.
>
> sysctl stats report that the card is trigger a lot of tx_desc_fail2:
>        dev.em.0.tx_desc_fail2: 3431
>
>
Maybe try EM_MULTIQUEUE?

http://lists.freebsd.org/pipermail/freebsd-net/2011-April/028664.html

-- 
Adam Vande More