Livelock limit engaged?

[Erik Wikström]

On 2007-08-11 01:24, Dave Hayes wrote:
Matthew Dillon <dillon at apollo.backplane.com> writes:
 run vmstat -i
# vmstat -i
interrupt                   total       rate
clk                                              281783        437
atkbd0                                                4          0
sio0                                                  0          0
fdc0                                                  0          0
ppc0                                                 18          0
acpi0/em0                                             0          0
uhci0                                                 0          0
uhci1/uhci2/uhci3/twe0/fxp0/atapci1/atapci1     6766087      10506
ata0                                              12463         19
ata1                                                  0          0
irq19                                               101          0
swi_siopoll                                           0          0
swi_crypto/swi_camnet                                 0          0
swi_cambio                                            0          0
swi_vm                                                0          0
swi_taskq                                             0          0
Total                                           7060456      10963
Ok I see the interrupt in question. (I don't suppose there is any way to
move the USB interrupts to another less used IRQ?)
   Monitor your interrupt rate with systat -vm 1
   If the interrupt rate is normal for the workload on the machine,
There's a good question. Define "normal". :) I have no idea what normal
is, this is a brand new box.
Here's a vmstat -i from a production machine that is doing your basic
web/email/DNS:
# vmstat -i
interrupt                   total       rate
clk                                           784643353        281
atkbd0                                                1          0
sio0                                                  0          0
ppc0                                                  1          0
acpi0/em0                                             0          0
uhci0                                                 0          0
uhci1/uhci2/uhci3/twe0/fxp0/atapci1/atapci1    75223514         26
ata0                                              71880          0
ata1                                                  0          0
irq19                                                96          0
swi_siopoll                                           0          0
swi_crypto/swi_camnet                                 0          0
swi_cambio                                            0          0
swi_vm                                                0          0
swi_taskq                                             0          0
Total                                         859938845        308
The two machines are supposed to be identical, but obviously they
aren't. (The last one was bought recently, the previous one in April.)
If I do your systat -vm 1, I hardly see a peak interrupt rate on
the production machine, but the new machine spikes to 30-40%. 

Both motherboards are D946GZIS Intel, identical as far as I can 
tell from the model and packaging. 
Just a guess (since this is not my area) but have you checked if they 
have the same BIOS revision? It might be possible that the newer one 
have an updated BIOS.

--
Erik Wikström