Freebsd 11.0 - system freeze on intensive I/O

[Gautam]

Hi,

I raised this topic on freebsd-questions where I suspect a bug caused due
to swapfile usage on FreeBSD.

You could read details in the below thread, but summary is that with using
a swapfile (not a swap partition) the system freezes on some single process
intensive I/O. This is 100% reproducible.

http://marc.info/?l=freebsd-questions&m=150088763825675&w=2

I raised a PR - 220971 ; but there are no backtraces / logs etc. that could
possibly help.

I would like to help narrow this down, but do not know how. Any suggestions
on how to debug a system freeze and what I need to do ? I could then try to
reproduce this and collect the needed information - traces etc.

Thanks,
Gautam