ep0 Interrupt Storm, 3Com EtherLink III (PnP)

[Billy Newsom]

Does anyone know exactly what to do about an interrupt storm, or if it 
really is a problem? I have an old system acting as a router/firewall. 
It is a dual processor, so I use SMP. But since going to 5.3 and 5.4, it 
would seem that this system runs a bit worse than under 4.7. It could be 
based on just an old BIOS, which will never be updated now, which 
doesn't support some of the new stuff. It's not ACPI, and PnP seems to 
be marginal as it always has been.

Other than the dmesg output, I would know nothing about such a storm. 
Since it is happening to a network card, I was wondering if it needs to 
be addressed.

I also don't know about the "unknown: <PNP0303> can't assign resources 
(port)" errors.

But back to the main issue, what is the storm all about?

# vmstat -i
interrupt                          total       rate
irq1: atkbd0                         634          0
irq5: ep0                        1037411          2
irq6: fdc0                            10          0
irq8: rtc                       58059776        127
irq14: ata0                      7724041         17
irq15: ata1                        29416          0
irq18: rl0                       2068244          4
irq0: clk                       45353879         99
Total                          114273411        251


*dmesg output (Storm is near the last line):
FreeBSD 5.4-STABLE #0: Mon Jul  4 18:28:47 CDT 2005
     root at me.dd.dd:/usr/obj/usr/src/sys/BILLYSMP3
Timecounter "i8254" frequency 1193182 Hz quality 0
CPU: Pentium Pro (199.31-MHz 686-class CPU)
   Origin = "GenuineIntel"  Id = 0x617  Stepping = 7
 
Features=0xfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV>
real memory  = 536870912 (512 MB)
avail memory = 515719168 (491 MB)
MPTable: <IBM-PCCO CrossFire MP>
FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs
  cpu0 (BSP): APIC ID:  1
  cpu1 (AP): APIC ID:  0
ioapic0: Assuming intbase of 0
ioapic0 <Version 1.1> irqs 0-23 on motherboard
npx0: <math processor> on motherboard
npx0: INT 16 interface
cpu0 on motherboard
cpu1 on motherboard
pcib0: <MPTable Host-PCI bridge> pcibus 0 on motherboard
pci0: <PCI bus> on pcib0
isab0: <PCI-ISA bridge> at device 1.0 on pci0
isa0: <ISA bus> on isab0
atapci0: <Intel PIIX3 WDMA2 controller> port 
0xfff0-0xffff,0x376,0x170-0x177,0x3f6,0x1f0-0x1f7 at device 1.1 on pci0
ata0: channel #0 on atapci0
ata1: channel #1 on atapci0
uhci0: <Intel 82371SB (PIIX3) USB controller> port 0x5400-0x541f irq 19 
at device 1.2 on pci0
usb0: <Intel 82371SB (PIIX3) USB controller> on uhci0
usb0: USB revision 1.0
uhub0: Intel UHCI root hub, class 9/0, rev 1.00/1.00, addr 1
uhub0: 2 ports with 2 removable, self powered
rl0: <D-Link DFE-530TX+ 10/100BaseTX> port 0x5000-0x50ff mem 
0x50000000-0x500000ff irq 18 at device 6.0 on pci0
miibus0: <MII bus> on rl0
rlphy0: <RealTek internal media interface> on miibus0
rlphy0:  10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto
rl0: Ethernet address: 00:50:ba:4d:57:6f
pci0: <display, VGA> at device 11.0 (no driver attached)
orm0: <ISA Option ROM> at iomem 0xc0000-0xc7fff on isa0
fdc0: <Enhanced floppy controller> at port 0x3f0-0x3f5 irq 6 drq 2 on isa0
fd0: <1440-KB 3.5" drive> on fdc0 drive 0
atkbdc0: <Keyboard controller (i8042)> at port 0x64,0x60 on isa0
atkbd0: <AT Keyboard> irq 1 on atkbdc0
kbd0 at atkbd0
vga0: <Generic ISA VGA> at port 0x3c0-0x3df iomem 0xa0000-0xbffff on isa0
sc0: <System console> at flags 0x100 on isa0
sc0: VGA <6 virtual consoles, flags=0x300>
sio0 at port 0x3f8-0x3ff irq 4 flags 0x10 on isa0
sio0: type 16550A
sio1 at port 0x2f8-0x2ff irq 3 on isa0
sio1: type 16550A
ppc0: <Parallel port> at port 0x378-0x37f irq 7 on isa0
ppc0: SMC-like chipset (ECP/EPP/PS2/NIBBLE) in COMPATIBLE mode
ppc0: FIFO with 16/16/8 bytes threshold
ppbus0: <Parallel port bus> on ppc0
lpt0: <Printer> on ppbus0
lpt0: Interrupt-driven port
ppi0: <Parallel I/O> on ppbus0
ep0: <3Com 3C509B-TPO EtherLink III (PnP)> at port 0x210-0x21f irq 5 on isa0
ep0: Ethernet address: 00:a0:24:6c:1b:46
unknown: <PNP0303> can't assign resources (port)
unknown: <PNP0700> can't assign resources (port)
unknown: <PNP0501> can't assign resources (port)
unknown: <PNP0401> can't assign resources (port)
unknown: <IBM37a0> can't assign resources (port)
Timecounters tick every 10.000 msec
IP Filter: v3.4.35 initialized.  Default = pass all, Logging = enabled
Interrupt storm detected on "irq5: ep0"; throttling interrupt source
ad0: 8809MB <QUANTUM FIREBALLP KA9.1/A42.0400> [17898/16/63] at 
ata0-master WDMA2
ad2: 2014MB <WDC AC22100H/10.07H11> [4092/16/63] at ata1-master WDMA2
acd0: DVDROM <TOSHIBA DVD-ROM SD-M1212/1R14> at ata1-slave PIO4
SMP: AP CPU #1 Launched!
Mounting root from ufs:/dev/ad0s1a