Freeze when running freebsd-update

[Robert Simmons]

On Tue, Jun 26, 2012 at 8:22 PM, Marten Vijn <info at martenvijn.nl> wrote:
> On 06/27/2012 12:32 AM, Robert Simmons wrote:
>>
>> I've run into a totally reproducible freeze in 9.0.  There are a
>> number of variables involved, but I'm able to reproduce this freeze
>> 100% of the time.
>>
>> I'm installing very small servers in a Xen HVM virtualization
>> environment.  Each instance has 128M memory and 4G of disk space.
>> There is 384M of swap encrypted using geli_swap_flags="-d -l 256 -s
>> 4096".
>>
>> The rest of the disk space is encrypted with "geli init -b -v -a
>> hmac/sha256 -l 256 -s 4096 /dev/ada0p4".
>>
>> After I've installed a VPS in this way, I run the freebsd-update fetch
>> command and it freezes at:
>> Applying patches...
>>
>> I've been trying to diagnose the problem by running top and watching
>> what happens during this stage.  I noticed the following:
>>
>> 1) the box runs out of physical memory at this stage (totally
>> expected, that's why there is sufficient swap space).
>> 2) All the processes except 2 sleep:
>> 31 processes:  1 running, 29 sleeping, 1 waiting
>> 3) the box is responsive to hitting enter at the console (it produces
>> another login: prompt)
>> 4) sshd is asleep, so I can't ssh into the box
>> 5) if I try to login to the console, it lets me enter a username then
>> locks up totally, it does not present me with a password: prompt.
>> 6) it has not run out of swap, nowhere close:
>> Mem: 54M Active, 9524K Inact, 41M Wired, 24K Cache, 21M Buf, 32K Free
>> Swap: 384M Total, 6452K Used, 378M Free, 1% Inuse
>> 7) the moment it runs out of physical memory it begins being unresponsive
>>
>> Any idea what might be going on here?
>
> no sorry, but I may have encounted the same issue/behavior in a jail setup
> on freebsd 9.0 some month ago:
>
> jails stacked ro-mount and unionfs. In the url below is POC script to build
> 50 jails. I used (old) i386 hardware. More memory and faster cpu seems to
> delay this behavior, adding more jails on a bit faster system.
>
> http://martenvijn.nl/mk_jail.sh

I've done some testing using a VirtualBox VM with exactly the same
specs as the Xen HVM setup.  I installed ports/benchmarks/forkbomb,
and I am able to reproduce the exact same freeze with "forkbomb -f".