My un-authoritative answer: I've been tracking this bug (or several with the
same symptoms) for going on a couple years. It's ridiculously common,
apparently well known to the Xen/Xensource guys judging by the number of
reports/bugs posted, but I haven't seen mention of it actually being addressed
and resolved. Unfortunately I see the same issue with it cropping up after VM
moves, though it occurs /every/ time there is a VM migration, once per
processor in the VM; doesn't matter if there is any IO on the Dom0 or DomU.
Occasionally VM's die during a migration and have to be manually
destroyed/restarted.
I do see evidence of significant instability (not implying it is related to the
above softlockup issues) however, in either VM moves migrating from a Xeon
(5345) to Opteron Dom0, and in high-utilization DomU's which are just plain
flaky and reboot/die semi-frequently even when never altered from their start Dom0.
For me, it currently means running only low-priority non-production services in
a VM, and not shelling out for RHEL5 support for the project (contrary to what
I planned) since it's not being addressed. I'd be curious if this is being
addressed in the Xen 3.2 release for RHEL5*...
Cheers,
/eli
Brett Worth wrote:
Hello All.
I've just started looking into Xen and have a test environment in
place. I'm seeing an
annoying problem that I thought worthy of a post.
Config:
I have 2 x HP DL585 servers each with 4 Dual core Opterons (non-vmx) and
16GB RAM
configured as Xen servers. These run CentOS 5.1 with the latest updates
applied. These
system both attach to an iSCSI target which is an HP DL385 running ietd
and serving SAN
based storage.
I have a test VM running CentOS 5.1 also updated.
Problem:
If I run the VM on a single server everything is OK. If I do a migrate
of the VM to the
other server I start getting random "BUG: soft lockup detected on CPU#?"
messages on the
VM console. The messages seem to happen with IO but not every time. A
reboot of the VM
on the new server will stop these messages.
I've also left the VM running overnight a couple of times and when I do
I find that any
external sessions (ssh) are hung in the morning but the console session
is not. New ssh
sessions can be started and seem to work.
After much googling it looks like the kernel messages can occur if dom0
is very busy but
mine is not.
Any suggestions?
Regards
Brett Worth
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