em interrupt storm

[Kris Kennaway]

On Thu, Nov 24, 2005 at 12:40:24PM +1100, Michael Vince wrote:


> chipset in all their servers.
> Luckily I haven't not seen the problem on any of my Dell servers (as 
> long as I am looking at this right).
> 
> This server has been running for a long time.
> vmstat -i
> interrupt                          total       rate
> irq1: atkbd0                           6          0
> irq4: sio0                         23433          0
> irq6: fdc0                            10          0
> irq8: rtc                     2631238611        128
> irq13: npx0                            1          0
> irq14: ata0                           99          0

The interrupt storm only happens when other interrupts are delivered
to other devices, e.g. when you're doing a lot of filesystem I/O.
 
> irq16: uhci0                  1507608958         73
> irq64: em0                    1513106157         73

Both of these look like they might be experiencing it, since they have
extremely high counts.  Your USB controller shouldn't have that many
interrupts, for example.

> 1000 simultaneous tcp connections under a load of 35. Both seem OK.
> vmstat -i
> interrupt                          total       rate
> irq4: sio0                           315          0
> irq13: npx0                            1          0
> irq14: ata0                           47          0
> irq16: uhci0                     2894669          2
> irq64: em0                       2890414          2

Again uhci seems to have a lot of interrupts.

Kris
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