SMP and interrupt storm

[Tech Lab Manager]

Hello,

Sorry for the semi-cross-post from freebsd-questions but I didn't get  
any bites there.

Building 6.3-RELEASE on dual Xeon (4 CPU) boxes:

	options         SMP
	device          apic

SMP kernel builds fine, all 4 CPUs launch on reboot.
But I get a TON of interrupts from acpi0 -- about 67,000 per second  
according to vmstat -i. With system at idle with almost no services  
running, here is output of top -S:

last pid:   877;  load averages:  1.18,  0.48,  0.19
75 processes:  6 running, 54 sleeping, 15 waiting
CPU states:  0.0% user,  0.0% nice,  0.2% system, 22.4% interrupt,  
77.4% idle
Mem: 31M Active, 12M Inact, 28M Wired, 16K Cache, 15M Buf, 3822M Free
Swap: 4096M Total, 4096M Free

   PID USERNAME   THR PRI NICE   SIZE    RES STATE  C   TIME   WCPU  
COMMAND
    10 root         1 171   52     0K     8K RUN    3   1:11 99.18%  
idle: cpu3
    13 root         1 171   52     0K     8K CPU0   0   1:10 98.88%  
idle: cpu0
    12 root         1 171   52     0K     8K CPU1   1   1:09 98.78%  
idle: cpu1
    21 root         1 -52 -171     0K     8K CPU2   2   0:54 87.24%  
irq9: acpi0
    11 root         1 171   52     0K     8K RUN    2   0:17 11.19%  
idle: cpu2

Notice high load and interrupt %.
Same thing happened with 7.0-RELEASE_BETA4.

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

The BIOS ACPI settings are all Enabled. Hyperthreading is Enabled.  
These machines have been running RedHat Enterprise 5.0 with full  
multiprocessor support.

Any pointers? TIA.
-- John

-- 
John Berliner
Live Oak School
http://www.liveoaksf.org