Kernel hang on 6.x

[Brad L. Chisholm]

On Wed, Jan 10, 2007 at 05:53:24PM -0500, John Baldwin wrote:
> On Wednesday 10 January 2007 16:52, Brad L. Chisholm wrote:
> > 
> > I work with Brian, and have been helping him analyze this problem.  We have
> > been able to generate kernel dumps, and have also done some additional
> > analysis under ddb.  Here is a summary of our analysis so far.  Suggestions
> > as to how to proceed from here are most welcome.
> 
> How much swap do you have?  You might have run out of buckets in the
> swap_zone before you ran out of swap space, in which case the kernel
> deadlocks rather than killing the hog like it does when it runs out of
> swap space.  I added a printf to catch this on HEAD recently that will
> be MFC'd soonish.  You can try bumping up kern.maxswzone (loader tunable).
> 

It has a 32GB swap partition.  We have also run it configured with an 
additional 32GB swap file, for a total of 64GB.  Changing the amount of
swap did not seem to affect the hang.  However, as I mentioned in my
previous post, the hang appears to always occur when ~14GB of swap have
been consumed, regardless of the amount of swap or physmen configured.
This does make it sound like a limit (such as swap_zone buckets) has 
been reached.

I notice the following in the vm.zone output captured just prior to 
a hang.  Does this value correspond to the swap_zone you were referring
to?  This looks like a limit may have been reached.

SWAPMETA:        288,   116519, 116519,      0,   116543


I don't seem to be able to query kern.maxswzone on our 6.2-BETA2 image:

# sysctl kern.maxswzone
sysctl: unknown oid 'kern.maxswzone'

Is it available in 6.x, or is it something newer?

Thanks!

---
Brad Chisholm
blc at bsdwins.com