[Fwd: Interrupts question]

Alex Zbyslaw xfb52 at dial.pipex.com
Mon Jul 17 16:41:14 UTC 2006

John Baldwin wrote:

>On Monday 17 July 2006 10:22, Alex Zbyslaw wrote:
>>No responses from questions at .  Anyone here understand what's going on?  
>>I was monitoring a machine with "systat -vmstat" and noticed something
>>about the interrupts and I don't know if it's a problem or not. If it
>>is a problem, is there anything I can do about it?
>>The interrupts for the network interface (em0) on irq 64 exactly match
>>those for a uhc device on irq 16.
>>And the interrupts for the hardware raid (amr) on irq 46 exactly match
>>those for a uhc device on irq 18.
>>The machine is a Dell 2850 running 5.4. Relevant bits from the dmesg are:
>FAQ.  It's due to brain damage in the Intel PCIX hubs and can't be fixed
Thanks.  I did search and couldn't find anything; guess I didn't search 
for the right thing :-(

Any idea how much this might impact performance, especially of the disk?

One thing I realised I missed from original dmesg was

> Interrupt storm detected on "irq18: uhci2"; throttling interrupt source

which ties to the disk interrupt.  Will that be slowing things down?  
Would increasing the storm threshold help (especially disk 
performance)?  Guess I'm looking for any mitigation that might be possible.

Thanks again,


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