kern/104406: [ufs] Processes get stuck in "ufs" state under persistent CPU load

[Rainer Hurling]

Kris Kennaway schrieb:
> Rainer Hurling wrote:
>> Thanks for your answer.
>>
>> Kris Kennaway schrieb:
>>> Rainer Hurling wrote:
>>>> Looking into PR kern/104406 it seems, that this describes exactly 
>>>> what I am experiencing on three of my systems over the last weeks. 
>>>> They are running FreeBSD 8.0-CURRENT (known as 7.0-CURRENT not long 
>>>> ago ;-) ).
>>>
>>> Actually it sounds nothing like it at all ;)
>>>
>>>> On these machines I often observe hangings, sometimes only a few 
>>>> seconds, on other times 20-30 seconds before input/output is back. 
>>>> This seems to happen when more extensive disk usage is needed 
>>>> (portupgrade, buildworld, browsing complicated websites etc.). 
>>>> During the hang even xterm is not responding any more, other 
>>>> (diskless) applications like xclock keep to continue. I have no 
>>>> panics, only UFS (and MSDOSFS) are mounted, no NTFS. About two 
>>>> months ago none of my systems showed these hangings.
>>>
>>> Is your system swapping?  This is the usual cause of pauses during 
>>> high application (actually memory) load.
>>>
>>> Kris
>>
>> No, I am working with 2GB RAM, without swapping at all.
>>
>> In the meantime I tested the above described behaviour a little more. 
>> The hangings even appeared without using Xorg, only working on 
>> consoles under heavy disk usage (portupgrade etc.).
> 
> OK, configure the system with the debugger and when it is "hung", break 
> to DDB and obtain the data requested in the developers handbook to try 
> and investigate what is going on.  You may want to do this a few times 
> to make sure you capture a representative sample.
> 
> Kris

I hope to find some time on tomorrow for my first session in kernel 
debugging ;-)

Am I right with chapter 'on-line kernel debugging using ddb'?
What kind of information is most usefull?

Rainer