6.1-STABLE hangs, ddb shows 'acpi_timer_read'?

[Karl Pielorz]

--On 20 October 2006 13:47 +0100 Robert Watson <rwatson at FreeBSD.org> wrote:

>> I'm just a little hesitant to put it all in, and end up with a machine
>> that's 80% slower :(
>
> Depends a lot on your workload.  WITNESS used to really, really slow
> things down for kernel lock intensive workloads (VFS especially); now it
> just really slows things down.  INVARIANTS overhead is generally
> measurable, but for most workloads it is likely <20%.  The place
> INVARIANTS hits you is when the kernel is allocating and freeing lots of
> memory, during which INVARIANTS will be scrubbing and checking for use
> after free, etc.  It's worth running with WITNESS when debugging
> deadlocks if possible, because it is, essentially, a deadlock debugging
> tool.  A moderate number of people run with INVARIANTS in production, but
> you generally don't want to do that with WITNESS.

Well this is happening on an almost daily basis for me, so I threw 
everything in. I'd rather have lousy performance for a couple of days - and 
get all the info needed to fix the problem, than fsck a terrabyte, and mop 
up after a hung machine daily ;)

Thanks for the replies, crossing fingers now :)

-Karl