interrupt throttling stepping in too soon?

[Stijn Hoop]

Followup to my own problem:

On Thu, Oct 06, 2005 at 09:53:12AM +0200, Stijn Hoop wrote:
> On the console there were multiple DMA_TIMEOUT messages for the disks of
> the array, and just above those was a line about an 'interrupt storm for
> atapci0, throttling'.

After a rebuild which completed succesfully, I rsynced data to the disks.
About 5 minutes later the same message appeared and the machine panic'd,
this time destroying /var/log with it :-/

Anyway, I decided to hammer the disks without waiting a long time for gvinum 
to build an array, and indeed I can reproduce this by mounting all 4 drives,
and for each drive dd'ing the whole drive to /dev/null plus rsync'ing data
to it at the same time. It held up at 20 MB/s but I suspect that the box
isn't keeping up with the combined total of interrupts because it goes down
faster when I engage the network (rsync from a remote box).

So, I guess my question becomes: is there a way to find out why this box
can't handle enough interrupts? Could it be that the motherboard is flawed?
Is this definitely a hardware error or is it still possible that the
interrupt throttling is stepping in too soon and thus screwing the rest
of the system?

On a sidenote, I monitored systat -vmstat while doing the above and it
appeared that IRQ 11 (ATA controller) was doing around 1000-1100
irqs/s, and IRQ 5 (xl0) was doing around 800-1000 irqs/s. Is there a
way to log this somehow?

*grumbling-something-about-i386-hardware*'ingly yours,

--Stijn

-- 
"Linux has many different distributions, meaning that you can probably find
one that is exactly what you want (I even found one that looked like a Unix
system)."
		-- Mike Meyer, from a posting at questions at freebsd.org
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