Re: High interrupt CPU usage in top

[Mark Cullen <mark.r.cullen@xxxxxxxxx>]

Oliver Fromme wrote:
> Mark Cullen <mark.r.cullen@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.