sio interrupt-level buffer overflows

Tarasov Oleg subscriber at
Wed Mar 23 01:33:46 PST 2005


I have FreeBSD 5.3-STABLE installed. Since I've installed a new 115200
Kbit/s modem and established ppp connection using kernel ppp, I
started recieving following messages:

sio0: 296 more interrupt-level buffer overflows (total 57038)

This message repeats almost every minute meaning serious malfunction
in the channel.

Bruce Evans <bde at> wrote in

> Try changing this line in sio.c:
>       cp4ticks = speed / 10 / hz * 4;
> to something like:
>       cp4ticks = speed / 10 / hz * 40;
> or if you use a non-default value for hz (default is 100):
>        cp4ticks = speed / 10 / 100 * 40;

the change to

       cp4ticks = speed / 10 / hz * 40;

made my kernel panic every 20 minutes
I use ipfw with dummynet and have set following all recommendations


in my kernel configuration. So, we have

cp4ticks = speed / 10 / 100 * 40  == speed / 10 / 1000 * 4

(what is the default, unchanged value) and must work properly
but due to unproper interrupt latency we have these overflows.
So, changing cp4ticks to

       cp4ticks = speed / 10 / hz * 40; == speed / 10 / 1000 * 40

made my kernel panic.
Then my second test was a multiplyer value of 16:
       cp4ticks = speed / 10 / hz * 16;
No panics but still interrupt-level buffer overflows (but 3 times less
than before)
It seems that I'll find that magic value on balance between
performance and stability of the system. But that is not a way.

My sympthoms are quite alike

here is my dmesg:

Timecounter "i8254" frequency 1193182 Hz quality 0
CPU: Intel(R) Pentium(R) III CPU family      1133MHz (1132.80-MHz 686-class CPU)
  Origin = "GenuineIntel"  Id = 0x6b1  Stepping = 1
real memory  = 536805376 (511 MB)
avail memory = 515624960 (491 MB)
FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs
 cpu0 (BSP): APIC ID:  0
 cpu1 (AP): APIC ID:  1
ioapic0 <Version 1.1> irqs 0-23 on motherboard
npx0: [FAST]
npx0: <math processor> on motherboard
npx0: INT 16 interface
acpi0: <VIA694 AWRDACPI> on motherboard
acpi0: Power Button (fixed)
Timecounter "ACPI-fast" frequency 3579545 Hz quality 1000
acpi_timer0: <24-bit timer at 3.579545MHz> port 0x4008-0x400b on acpi0
cpu0: <ACPI CPU (3 Cx states)> on acpi0
cpu1: <ACPI CPU (3 Cx states)> on acpi0
acpi_tz0: <Thermal Zone> on acpi0
acpi_button0: <Power Button> on acpi0
pcib0: <ACPI Host-PCI bridge> port 0x5000-0x500f,0x4080-0x40ff,0x4000-0x407f,0xcf8-0xcff on acpi0
pci0: <ACPI PCI bus> on pcib0
agp0: <VIA Generic host to PCI bridge> mem 0xf0000000-0xf3ffffff at device 0.0 on pci0
pcib1: <PCI-PCI bridge> at device 1.0 on pci0
pci1: <PCI bus> on pcib1
pci1: <display, VGA> at device 0.0 (no driver attached)
atapci0: <Promise PDC20267 UDMA100 controller> port 0xb000-0xb03f,0xac00-0xac03,0xa800-0xa807,0xa400-0xa403,0xa000-0xa007 mem 0xfb100000-0xfb11ffff irq 18 at device 12.0 on pci0
ata2: channel #0 on atapci0
ata3: channel #1 on atapci0
fxp0: <Intel 82559 Pro/100 Ethernet> port 0xb400-0xb43f mem 0xfb000000-0xfb0fffff,0xfb120000-0xfb120fff irq 19 at device 13.0 on pci0
miibus0: <MII bus> on fxp0
inphy0: <i82555 10/100 media interface> on miibus0
inphy0:  10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto
fxp0: Ethernet address: 00:30:48:41:17:32
isab0: <PCI-ISA bridge> at device 17.0 on pci0
isa0: <ISA bus> on isab0
atapci1: <VIA 8233 UDMA100 controller> port 0xb800-0xb80f,0x376,0x170-0x177,0x3f6,0x1f0-0x1f7 at device 17.1 on pci0
ata0: channel #0 on atapci1
ata1: channel #1 on atapci1
uhci0: <VIA 83C572 USB controller> port 0xbc00-0xbc1f irq 10 at device 17.2 on pci0
usb0: <VIA 83C572 USB controller> on uhci0
usb0: USB revision 1.0
uhub0: VIA UHCI root hub, class 9/0, rev 1.00/1.00, addr 1
uhub0: 2 ports with 2 removable, self powered
uhci1: <VIA 83C572 USB controller> port 0xc000-0xc01f irq 10 at device 17.3 on pci0
usb1: <VIA 83C572 USB controller> on uhci1
usb1: USB revision 1.0
uhub1: VIA UHCI root hub, class 9/0, rev 1.00/1.00, addr 1
uhub1: 2 ports with 2 removable, self powered
uhci2: <VIA 83C572 USB controller> port 0xc400-0xc41f irq 10 at device 17.4 on pci0
usb2: <VIA 83C572 USB controller> on uhci2
usb2: USB revision 1.0
uhub2: VIA UHCI root hub, class 9/0, rev 1.00/1.00, addr 1
uhub2: 2 ports with 2 removable, self powered
fdc0: <floppy drive controller> port 0x3f7,0x3f0-0x3f5 irq 6 drq 2 on acpi0
fdc0: [FAST]
fd0: <1440-KB 3.5" drive> on fdc0 drive 0
sio0: <16550A-compatible COM port> port 0x3f8-0x3ff irq 4 flags 0x10 on acpi0
sio0: type 16550A
sio1: <16550A-compatible COM port> port 0x2f8-0x2ff irq 3 on acpi0
sio1: type 16550A
ppc0: <ECP parallel printer port> port 0x778-0x77b,0x378-0x37f irq 7 drq 3 on acpi0
ppc0: SMC-like chipset (ECP/EPP/PS2/NIBBLE) in COMPATIBLE mode
ppc0: FIFO with 16/16/16 bytes threshold
ppbus0: <Parallel port bus> on ppc0
plip0: <PLIP network interface> on ppbus0
lpt0: <Printer> on ppbus0
lpt0: Interrupt-driven port
ppi0: <Parallel I/O> on ppbus0
atkbdc0: <Keyboard controller (i8042)> port 0x64,0x60 irq 1 on acpi0
atkbd0: <AT Keyboard> irq 1 on atkbdc0
kbd0 at atkbd0
atkbd0: [GIANT-LOCKED]
psm0: <PS/2 Mouse> irq 12 on atkbdc0
psm0: model IntelliMouse Explorer, device ID 4
orm0: <ISA Option ROMs> at iomem 0xcc000-0xd3fff,0xc0000-0xc7fff on isa0
pmtimer0 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
Timecounters tick every 1.000 msec
ipfw2 initialized, divert enabled, rule-based forwarding enabled, default to accept, logging limited to 300 packets/entry by default
ad4: 57241MB <ST360021A/3.19> [116301/16/63] at ata2-master UDMA100
ad6: 57241MB <ST360021A/3.19> [116301/16/63] at ata3-master UDMA100
ar0: 57241MB <ATA RAID1 array> [7297/255/63] status: READY subdisks:
 disk0 READY on ad4 at ata2-master
 disk1 READY on ad6 at ata3-master
SMP: AP CPU #1 Launched!

Best regards,
 Tarasov Oleg                          mailto:subscriber at

More information about the freebsd-bugs mailing list