Network sort of stops working with the em (intel) driver under load.

[mark rowlands]

Newly built and cvsupped system,with GENERIC kernel,  when copying
large amounts of data over a gigabit link via scp  the network  will
hang after a couple of gig.  I can then no longer login via ssh. If I
leave it be, after about 12-24 hours I can then login again. (A reboot
of course fixes the issue immediately...) .

The system is very vanilla, only accf_http in loader.conf. No sysctl
tuning done, no firewall hankypanky.

pciconf -lv | grep -A4 ^em
em0 at pci0:3:4:0: class=0x020000 card=0x001e8086 chip=0x100e8086 rev=0x02 hdr=0x00
    vendor     = 'Intel Corporation'
    device     = 'Gigabit Ethernet Controller (82540EM)'
    class      = network
    subclass   = ethernet

em0: <Intel(R) PRO/1000 Legacy Network Connection 1.0.1> port
0xec00-0xec3f mem 0xfeae0000-0xfeafffff,0xff irq 17 at device 4.0 on
pci3

Suggestions as to where I could look for more information as to the
precise nature of the problem gratefully received.  Current plan is to
purchase another variety of gigabit card to see if it is specific to
the intel card.

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FreeBSD 8.1-PRERELEASE #0: Sun May 30 10:00:58 CEST 2010
    root at temp.mwrwin2k.se:/usr/obj/usr/src/sys/MARK2 i386
Timecounter "i8254" frequency 1193182 Hz quality 0
CPU: Intel(R) Pentium(R) 4 CPU 3.40GHz (3391.53-MHz 686-class CPU)
  Origin = "GenuineIntel"  Id = 0xf34  Family = f  Model = 3  Stepping = 4
  Features=0xbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
  Features2=0x441d<SSE3,DTES64,MON,DS_CPL,CNXT-ID,xTPR>
  TSC: P-state invariant
real memory  = 2147483648 (2048 MB)
avail memory = 2090823680 (1993 MB)
ACPI APIC Table: <A M I  OEMAPIC >
FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs
FreeBSD/SMP: 1 package(s) x 1 core(s) x 2 HTT threads
 cpu0 (BSP): APIC ID:  0
 cpu1 (AP/HT): APIC ID:  1
ioapic0: Changing APIC ID to 2
ioapic1: Changing APIC ID to 3
ioapic0 <Version 0.3> irqs 0-23 on motherboard
ioapic1 <Version 0.3> irqs 24-47 on motherboard
kbd1 at kbdmux0
acpi0: <A M I OEMRSDT> on motherboard
acpi0: [ITHREAD]
acpi0: Power Button (fixed)
acpi0: reservation of fec00000, 1000 (3) failed
acpi0: reservation of fee00000, 1000 (3) failed
acpi0: reservation of 0, a0000 (3) failed
acpi0: reservation of 100000, 7ff00000 (3) failed
Timecounter "ACPI-fast" frequency 3579545 Hz quality 1000
acpi_timer0: <24-bit timer at 3.579545MHz> port 0x808-0x80b on acpi0
cpu0: <ACPI CPU> on acpi0
cpu1: <ACPI CPU> on acpi0
pcib0: <ACPI Host-PCI bridge> port 0xcf8-0xcff on acpi0
pci0: <ACPI PCI bus> on pcib0
pcib1: <ACPI PCI-PCI bridge> at device 1.0 on pci0
pci1: <ACPI PCI bus> on pcib1
vgapci0: <VGA-compatible display> port 0xd000-0xd0ff mem
0xc0000000-0xcfffffff,0xfe9e0000-0xfe9effff irq 16 at device 0.0 on
pci1
vgapci1: <VGA-compatible display> mem
0xd0000000-0xdfffffff,0xfe9f0000-0xfe9fffff at device 0.1 on pci1
pcib2: <ACPI PCI-PCI bridge> irq 27 at device 2.0 on pci0
pci2: <ACPI PCI bus> on pcib2
atapci0: <VIA 8237 SATA300 controller> port
0xcc00-0xcc07,0xc880-0xc883,0xc800-0xc807,0xc480-0xc483,0xc400-0xc40f,0xc000-0xc0ff
irq 21 at device 15.0 on pci0
atapci0: [ITHREAD]
ata2: <ATA channel 0> on atapci0
ata2: [ITHREAD]
ata3: <ATA channel 1> on atapci0
ata3: [ITHREAD]
atapci1: <VIA 8237 UDMA133 controller> port
0x1f0-0x1f7,0x3f6,0x170-0x177,0x376,0xfc00-0xfc0f at device 15.1 on
pci0
ata0: <ATA channel 0> on atapci1
ata0: [ITHREAD]
ata1: <ATA channel 1> on atapci1
ata1: [ITHREAD]
uhci0: <VIA 83C572 USB controller> port 0xb480-0xb49f irq 20 at device
16.0 on pci0
uhci0: [ITHREAD]
usbus0: <VIA 83C572 USB controller> on uhci0
uhci1: <VIA 83C572 USB controller> port 0xb800-0xb81f irq 22 at device
16.1 on pci0
uhci1: [ITHREAD]
usbus1: <VIA 83C572 USB controller> on uhci1
uhci2: <VIA 83C572 USB controller> port 0xb880-0xb89f irq 21 at device
16.2 on pci0
uhci2: [ITHREAD]
usbus2: <VIA 83C572 USB controller> on uhci2
uhci3: <VIA 83C572 USB controller> port 0xbc00-0xbc1f irq 23 at device
16.3 on pci0
uhci3: [ITHREAD]
usbus3: <VIA 83C572 USB controller> on uhci3
ehci0: <VIA VT6202 USB 2.0 controller> mem 0xfe8ffc00-0xfe8ffcff irq
21 at device 16.4 on pci0
ehci0: [ITHREAD]
usbus4: EHCI version 1.0
usbus4: <VIA VT6202 USB 2.0 controller> on ehci0
isab0: <PCI-ISA bridge> at device 17.0 on pci0
isa0: <ISA bus> on isab0
vr0: <VIA VT6102 Rhine II 10/100BaseTX> port 0xb000-0xb0ff mem
0xfe8ff800-0xfe8ff8ff irq 23 at device 18.0 on pci0
vr0: Quirks: 0x0
vr0: Revision: 0x7c
miibus0: <MII bus> on vr0
ukphy0: <Generic IEEE 802.3u media interface> PHY 1 on miibus0
ukphy0:  10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto
vr0: Ethernet address: 00:19:66:92:a0:3f
vr0: [ITHREAD]
pcib3: <ACPI PCI-PCI bridge> at device 19.1 on pci0
pci3: <ACPI PCI bus> on pcib3
em0: <Intel(R) PRO/1000 Legacy Network Connection 1.0.1> port
0xec00-0xec3f mem 0xfeae0000-0xfeafffff,0xfeac0000-0xfeadffff irq 17
at device 4.0 on pci3
em0: [FILTER]
em0: Ethernet address: 00:0e:0c:38:a8:ca
acpi_button0: <Sleep Button> on acpi0
acpi_button1: <Power Button> on acpi0
pcib4: <ACPI Host-PCI bridge> on acpi0
pci128: <ACPI PCI bus> on pcib4
pci128: <multimedia, HDA> at device 1.0 (no driver attached)
atrtc0: <AT realtime clock> port 0x70-0x71 irq 8 on acpi0
atkbdc0: <Keyboard controller (i8042)> port 0x60,0x64 irq 1 on acpi0
atkbd0: <AT Keyboard> irq 1 on atkbdc0
kbd0 at atkbd0
atkbd0: [GIANT-LOCKED]
atkbd0: [ITHREAD]
psm0: <PS/2 Mouse> irq 12 on atkbdc0
psm0: [GIANT-LOCKED]
psm0: [ITHREAD]
psm0: model Generic PS/2 mouse, device ID 0
pmtimer0 on isa0
orm0: <ISA Option ROMs> at iomem 0xc0000-0xccfff,0xcd000-0xce7ff pnpid
ORM0000 on isa0
sc0: <System console> at flags 0x100 on isa0
sc0: VGA <16 virtual consoles, flags=0x300>
vga0: <Generic ISA VGA> at port 0x3c0-0x3df iomem 0xa0000-0xbffff on isa0
ppc0: parallel port not found.
p4tcc0: <CPU Frequency Thermal Control> on cpu0
p4tcc1: <CPU Frequency Thermal Control> on cpu1
Timecounters tick every 1.000 msec
usbus0: 12Mbps Full Speed USB v1.0
usbus1: 12Mbps Full Speed USB v1.0
usbus2: 12Mbps Full Speed USB v1.0
usbus3: 12Mbps Full Speed USB v1.0
usbus4: 480Mbps High Speed USB v2.0
acd0: CDROM <SAMSUNG CD-ROM SC-148C/B105> at ata0-master UDMA33
ugen0.1: <VIA> at usbus0
uhub0: <VIA UHCI root HUB, class 9/0, rev 1.00/1.00, addr 1> on usbus0
ugen1.1: <VIA> at usbus1
uhub1: <VIA UHCI root HUB, class 9/0, rev 1.00/1.00, addr 1> on usbus1
ugen2.1: <VIA> at usbus2
uhub2: <VIA UHCI root HUB, class 9/0, rev 1.00/1.00, addr 1> on usbus2
ugen3.1: <VIA> at usbus3
uhub3: <VIA UHCI root HUB, class 9/0, rev 1.00/1.00, addr 1> on usbus3
ugen4.1: <VIA> at usbus4
uhub4: <VIA EHCI root HUB, class 9/0, rev 2.00/1.00, addr 1> on usbus4
ad4: 238475MB <WDC WD2500JD-55HBB0 08.02D08> at ata2-master UDMA100 SATA 1.5Gb/s
ad6: 238475MB <WDC WD2500JD-55HBB0 08.02D08> at ata3-master UDMA100 SATA 1.5Gb/s
SMP: AP CPU #1 Launched!
Root mount waiting for: usbus4 usbus3 usbus2 usbus1 usbus0
uhub0: 2 ports with 2 removable, self powered
uhub1: 2 ports with 2 removable, self powered
uhub2: 2 ports with 2 removable, self powered
uhub3: 2 ports with 2 removable, self powered
Root mount waiting for: usbus4
Root mount waiting for: usbus4
uhub4: 8 ports with 8 removable, self powered
ugen4.2: <Western Digital> at usbus4
umass0: <Western Digital External HDD, class 0/0, rev 2.00/1.75, addr
2> on usbus4
Root mount waiting for: usbus4
Trying to mount root from ufs:/dev/ad4s1a
da0 at umass-sim0 bus 0 scbus0 target 0 lun 0
da0: <WD 10EAVS External 1.75> Fixed Direct Access SCSI-4 device
da0: 40.000MB/s transfers
da0: 953869MB (1953525168 512 byte sectors: 255H 63S/T 121601C)