SMP kernel and interrupt storm

[John Berliner]

Building 6.3-RELEASE on dual Xeon boxes, SMP kernel builds fine, all  
4 CPUs launch on reboot.

	options         SMP
	device          apic

But I get a TON of interrupts from acpi0 -- about 68,000 per second  
according to vmstat -i. With system at idle with almost no services  
running, here is output of top -S:

last pid:  1026;  load averages:  0.94,  0.96,  0.91
63 processes:  6 running, 42 sleeping, 15 waiting
CPU states:  0.0% user,  0.0% nice,  0.0% system, 45.3% interrupt,  
54.7% idle
Mem: 9296K Active, 13M Inact, 28M Wired, 16K Cache, 17M Buf, 3843M Free
Swap: 4096M Total, 4096M Free

   PID USERNAME   THR PRI NICE   SIZE    RES STATE  C   TIME   WCPU  
COMMAND
    13 root         1 171   52     0K     8K RUN    0  42:54 99.02%  
idle: cpu0
    21 root         1 -52 -171     0K     8K CPU2   2  32:26 85.25%  
irq9: acpi0
    11 root         1 171   52     0K     8K RUN    2  10:33 12.74%  
idle: cpu2

Notice high load (0.94, often higher) and 45% interrupt.

If turn off ACPI (set hint.apic.0.disabled=1 in loader.conf), the  
interrupt 'storm' ceases, but then I'm only running on one CPU.

Help? -- John