em0 performance subpar

[Adam Stylinski]

On Thu, Apr 28, 2011 at 02:52:59PM +0100, Steven Hartland wrote:
> Running em's here we regularly see them hitting pretty much line rate
> although there are a lot of different em's
> 
> Here we have the following under 8.0+
> em0 at pci0:6:0:0: class=0x020000 card=0x000015d9 chip=0x10968086 rev=0x01 hdr=0x00
>     vendor     = 'Intel Corporation'
>     device     = 'Intel PRO/1000 EB (Intel PRO/1000 EB)'
>     class      = network
>     subclass   = ethernet
> 
> You don't say which OS version your running?
> 
>     Regards
>     Steve
> 
> ----- Original Message ----- 
> From: "Mike Tancsa" <mike at sentex.net>
> To: "Adam Stylinski" <kungfujesus06 at gmail.com>
> Cc: <freebsd-net at freebsd.org>
> Sent: Thursday, April 28, 2011 2:04 PM
> Subject: Re: em0 performance subpar
> 
> 
> > On 4/28/2011 3:29 AM, Adam Stylinski 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
> >
> > Try the tests using the tools in /usr/src/tools/tools/netperf to
> > generate / test udp traffic.
> >
> > Perhaps give the driver from HEAD a try. There are a few fixes to it. I
> > back ported it to RELENG_8, but it should work on 8.2R as well.
> >
> > http://www.tancsa.com/em-723.tgz
> >
> > what does pciconf -lvc for your em NIC show ?
> > also, vmstat -i
> >
> > ---Mike
> >
> >
> >
> > -- 
> > -------------------
> > Mike Tancsa, tel +1 519 651 3400
> > Sentex Communications, mike at sentex.net
> > Providing Internet services since 1994 www.sentex.net
> > Cambridge, Ontario Canada   http://www.tancsa.com/
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> > 
> 
> 
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I am running FreeBSD 8.2-RELEASE on one of the boxes with the issues, and the other box which has the same issue is 8-STABLE.  The issue doesn't seem isolated to one box though and like I said, Linux seems to not have this issue.

-- 
Adam Stylinski
PGP Key: http://pohl.ececs.uc.edu/~adam/publickey.pub
Blog: http://technicallyliving.blogspot.com
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