SMP, ACPI and interrupt storm

[Nate Lawson]

Tech Lab Manager wrote:
> Sorry for the cross-post from freebsd-smb.
> 
> Building 6.3-RELEASE and 7.0-RC1 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 and 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 % of CPU.
> 
> If turn off ACPI (e.g. set hint.apic.0.disabled=1 in /boot/loader.conf),
> the interrupt storm ceases, but then I'm only running on one CPU.

That doesn't turn off acpi, that turns of the APIC (interrupt 
controller).  Try:
  hint.acpi.0.disabled=1

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

This looks like a failure to sleep in C1 (hlt).  Someone else reported 
this probably earlier, but all debugging showed the inexplicable -- the 
HLT instruction was being executed but just did not work (returned 
immediately).

There will be a new 7.0 build that fixes one interrupt storm related to 
level-triggered GPEs.  If you can cvsup your 7.0 branch (RELENG_7_0) and 
retry, that might be helpful to see if it also fixes your problem.

-- 
Nate