em0 performance subpar

[Adam Stylinski]

On Thu, Apr 28, 2011 at 09:04:24AM -0400, Mike Tancsa wrote:
> 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/

lspci -lvc:

em0 at pci0:7:5:0: class=0x020000 card=0x13768086 chip=0x107c8086 rev=0x05 hdr=0x00
    vendor     = 'Intel Corporation'
    device     = 'Gigabit Ethernet Controller (Copper) rev 5 (82541PI)'
    class      = network
    subclass   = ethernet
    cap 01[dc] = powerspec 2  supports D0 D3  current D0
    cap 07[e4] = PCI-X supports 2048 burst read, 1 split transaction

vmstat -i:

interrupt                          total       rate
irq1: atkbd0                           6          0
irq14: ata0                        30306          1
irq18: ohci0 ohci1*                    5          0
irq20: em0                        994488         43
irq24: aac0                       107044          4
irq40: hptrr0                      89761          3
irq48: fwohci0+                     5047          0
cpu0: timer                     45466809       1999
irq256: ahci1                      83842          3
cpu2: timer                     45458298       1999
cpu3: timer                     45458296       1999
cpu1: timer                     45458295       1999
Total                          183152197       8055

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