RELENG_7: interrupt eating whole cpu core

Dominic Fandrey kamikaze at bsdforen.de
Wed Feb 6 19:45:05 UTC 2008


Chuck Swiger wrote:
> Hi, Dominic--
> 
> On Feb 6, 2008, at 11:12 AM, Dominic Fandrey wrote:
>>> behaviour has changed. This is an HP 6510b GR695EA#ABD, if anyone 
>>> thinks it might be helpful, I can supply you with a dmesg and the 
>>> output of pciconf -lv.
>>
>> The problem remains with fresh sources:
>>
>>  PID USERNAME   THR PRI NICE   SIZE    RES STATE  C   TIME    CPU COMMAND
>>   12 root         1 171 ki31     0K    16K RUN    0  22:04 97.85% 
>> idle: cpu0
>>   37 root         1 -64    -     0K    16K CPU1   1   2:35 96.00% 
>> irq14: ata0
>>   11 root         1 171 ki31     0K    16K RUN    1  19:32  6.40% 
>> idle: cpu1
>>
>> The rip is done by k3b, so the drive is accessed through the cam 
>> interface.
> 
> What are the values being reported by "sysctl hw.ata"?  If you're going 
> to be burning CD/DVDs, you really want to make sure hw.ata.atapi_dma is on.

I cannot believe it was so trivial. The sysctl looks all right.

# sysctl hw.ata                                      0 /root
hw.ata.wc: 1
hw.ata.atapi_dma: 1
hw.ata.ata_dma: 1

But further research revealed:
# atacontrol mode acd0                               0 /root
current mode = PIO4

# atacontrol mode acd0 udma33                        0 /root

changed the load dramatically:
  PID USERNAME    THR PRI NICE   SIZE    RES STATE  C   TIME   WCPU COMMAND
   12 root          1 171 ki31     0K    16K RUN    0  52:54 100.00% idle: cpu0
   11 root          1 171 ki31     0K    16K CPU1   1  23:36 94.29% idle: cpu1
1087 kamikaze      3  -8    0   133M 36168K physrd 1   1:09  3.17% k3b
   37 root          1 -64    -     0K    16K WAIT   1  30:10  0.00% irq14: ata0


Thank you very much! I used to think that UDMA33 was the default for 
CD-/DVD-Rom drives. I suppose I should review the BIOS settings or change 
something in the hints file.


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