kern/152828: [em] poor performance on 8.1, 8.2-PRE

[Rick Richard]

>Number:         152828
>Category:       kern
>Synopsis:       [em] poor performance on 8.1, 8.2-PRE
>Confidential:   no
>Severity:       serious
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sat Dec 04 09:30:15 UTC 2010
>Closed-Date:
>Last-Modified:
>Originator:     Rick Richard
>Release:        FreeBSD 8.2-PRERELEASE #3: Fri Dec  3 22:28:42 PST 2010
>Organization:
>Environment:
FreeBSD thinking.kicks-ass.org 8.2-PRERELEASE FreeBSD 8.2-PRERELEASE #3: Fri Dec  3 22:28:42 PST 2010     rrichard at thinking.kicks-as
s.org:/usr/obj/usr/src/sys/REASON  amd64
>Description:
The only additions to the kernel config are PF and ALTQ.

After upgrading from 8.0 to 8.1-RELEASE, throughput has been terrible with this card.  I have it connected to a 100baseTX switch.  Using iperf between this machine and another machine I measure only 1.80Mbits/sec coming in but the full 94.8Mbits/sec going out.  

I just upgraded to 8-STABLE hoping for some improvement, but the results are the same.

Now just to be sure, I copied the 8.0-RELEASE em / e1000 driver over to 8-STABLE, rebuilt the kernel, and measured 94.6Mbits/sec coming in and 87.4Mbits/sec going out.  It seems that the post-8.0 driver performs better when transmitting but there is something seriously wrong with the reception of traffic.

dmesg:
FreeBSD 8.1-RELEASE-p2 #2: Fri Dec  3 15:58:41 PST 2010
<snip>
em0: <Intel(R) PRO/1000 Legacy Network Connection 1.0.1> port 0xcc00-0xcc3f mem 0xfdfe0000-0xfdffffff,0xfdfc0000-0xfdfdffff irq 16 1
em0: [FILTER]
em0: Ethernet address: 00:07:e9:19:f0:cc

FreeBSD 8.2-PRERELEASE #3: Fri Dec  3 22:28:42 PST 2010
<snip>
em0: <Intel(R) PRO/1000 Legacy Network Connection 1.0.3> port 0xcc00-0xcc3f mem 0xfdfe0000-0xfdffffff,0xfdfc0000-0xfdfdffff irq 16 1
em0: [FILTER]
em0: Ethernet address: 00:07:e9:19:f0:cc

sysctl -a:
dev.em.0.%desc: Intel(R) PRO/1000 Legacy Network Connection 1.0.3
dev.em.0.%driver: em
dev.em.0.%location: slot=4 function=0
dev.em.0.%pnpinfo: vendor=0x8086 device=0x100e subvendor=0x8086 subdevice=0x002e class=0x020000
dev.em.0.%parent: pci1
<snip for being too long>

ifconfig -a:
em0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
        options=209b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM,WOL_MAGIC>
        ether 00:07:e9:19:f0:cc
        inet 24.176.175.198 netmask 0xfffffff8 broadcast 24.176.175.199
        media: Ethernet autoselect (100baseTX <full-duplex>)
        status: active
>How-To-Repeat:
Use same or similar chipset and compare performance between 8.0 and 8.1+

I believe the card is named "Intel PRO/1000 MT Desktop RT"
>Fix:


>Release-Note:
>Audit-Trail:
>Unformatted: