Re: Odd problem with many vcpus

[Cherry G.Mathew <cherry%zyx.in@localhost>]

Staffan Thomén <duck%shangtai.net@localhost> writes:

> Hey!
>
> I have a supermicro with two Xeon X5650 cpus (6-core, with HT so Xen
> and netbsd sees 24 cpus total) running netbsd/xen, I am using
> xenkernel and tools version 4.11, and all of the doms run 8.0_STABLE
>
> I noticed a problem with my build VM, a domU with 20 vcpus and 50GB of
> ram (out of a total of 70GB) since my big upgrade from -7 to -8 in
> that if I enable more than 12 vcpus and attempt to build firefox, the
> build will hang the system just after "Reticulating splines..."
>
> The (virtual) machine will answer pings and I am able to enter my
> username and password on the xen cosole, but I get no shell
> prompt. This smells to me like new processes can't be forked, and this
> is also what the mozilla configure script seems to be doing at that
> point, i.e. forking a lot.
>

Do you have any messages from dom0 (xl dmesg, /var/log/xen/... ) that
could help please ?

> The (build domU) system also feels slightly slower than netbsd-7, but
> I could well be imagning that.
>
> So what's going on here?
>

Hard to tell without more data. All you've given us is a process fork
related domU hang which isn't much to go on.

Would you be able to break into ddb, for eg: and give us a dmesg, ps and
other info ?

> The system is in production use, but since the build domU hanging
> doesn't seem to affect any other domU, I can try something out if you
> have suggestions.
>

More information the better. 

-- 
~cherry