High interrupt CPU usage in top

[Mark Cullen]

Oliver Fromme wrote:
Mark Cullen <mark.r.cullen at xxxxxxxxx> wrote:
 > I don't know if it is anything to be concerned about, but I seem to be 
 > seeing high interrupt CPU usage in top (at least) when compiling things...
 > 
 > ---
 > load averages:  0.81,  0.57,  0.36                      up 0+00:37:49 
 > 15:41:44
 > 43 processes:  2 running, 41 sleeping
 > CPU states: 37.1% user,  0.0% nice, 27.9% system, 35.0% interrupt,  0.0% idle

Have you tried "vmstat -i"?  It might give an indication
if any of the device interrupts is causing the problem.
I remember a similar problem on FreeBSD machines where the
USB interrupt was shared with the NIC interrupt.  The USB
interrupt handler is quite heavy-weight, so it slowed down
the processing of NIC interrupts, even if no actual USB
devices were in use at all.  Moving the USB controller to
a different interrupt (or disabling USB completely) solved
the problem.
Best regards
   Oliver
Yep, doesn't look particularly unusual to me (taken while compiling 
multiple things)?

interrupt                   total       rate
clk                       3134621        281
atkbd0                       5405          0
sio1                            0          0
sio0                            0          0
fxp0                       176854         15
ppc0                            1          0
acpi0                           0          0
uhci0/fxp1                      0          0
psm0                            0          0
ata0                           40          0
ata1                       250336         22
irq19                          51          0
swi_siopoll                     0          0
swi_crypto/swi_camnet           0          0
swi_cambio                      0          0
swi_vm                          0          0
swi_taskq                       0          0
Total                     3567308        319
Looks like USB is sharing with fxp1? Not that fxp1 is actually even 
plugged in or being used at all at the moment!! Unfortuantly disabling 
USB is not an option for me, I have a USB -> Serial converter which I 
need for the UPS.