strange i/o and tty lockups/delays on 6.1, strange sync() issue

[Marek Blaszkowski]

Nate Eldredge wrote:
> On Wed, 31 Oct 2007, Marek Blaszkowski wrote:
> 
>> Hi,
>> my config:
>> thunder k8sr, dual opteron 244, 8GB RAM, FreeBSD 6.1, sata disk
>>
>>
>> for time to time (every 10 or 20 secs) any process which try write or
>> read any, even small file, is locked for a couple seconds (about 7 or
>> 9 secs), very iritating when I try save small files edited in vim
>> (size about 2-3 kbytes), it's looks like this: #vim /path/to/file
>> ...editing..
>> :w
>> and now (afetr w command) vim freeze for 7-10 secs until it displays
>> "file written".
>>
>> Delays accours on tty, too. In vim I can't move around edited file
>> (up/down in rows), vim just got hang, strange is that I can switch
>> (durning vim lockup) beetwen virtual screen consoles.
> 
> 
> [sync takes a long time too]
> 
> Is there anything in the log files?  This might happen if the disk
> access fails or times out; the kernel resets the controller and tries
> again, which takes a long time.  That would indicate that the disk is
> probably failing, in which case it should be backed up and replaced as
> soon as possible.  You could also see if smartctl reports anything
> significant.
> 
> If that's not it, you might try running top and see if any process
> accumulated CPU seconds during the hang.
> 
> I experienced a couple of other issues where things would hang
> momentarily.  One was fixed by disabling ACPI (it's a long story) and
> the other by enabling PREEMPTION.  So if the disk is okay those are two
> more things you could try.
> 
> Hope this helps.  I'd be interested to know what you find out.

Does PREEMPTION option is safe for production servers now? I saw many threads on amd64@ or stable@
about kernel crashes with this option enabled, so I don't decided to use it...

regrads,
-- 
Marek B.