xen discuss - Apr 2010 - Console output blocks domU when console buffer gets full.

dom0:
SunOS xen01.unix 5.11 snv_134 i86pc i386 i86xpv
Compiled against library: libvir 0.7.0
Using library: libvir 0.7.0
Using API: Xen 3.0.1
Running hypervisor: Xen 3.4

domU:
SunOS ssh00.unix 5.10 Generic_141445-09 i86pc i386 i86pc

If I run a command that outputs a few lines on the console, ie, so that they
show up when connected with:
# virsh console ssh00.unix

the system works great.

If I disconnect "virsh console" (ctrl-]) and keep running the command
on domU, they will continue to work until the console buffer is full. About ~24
lines of text or so.

Then the domU will stop responding completely.

If I reconnect to console, via "virsh console", the buffer is emptied,
and the domU comes back to life.

Is this a known problem? Normally, domUs probably very rarely send IO on console
so that the buffer do not fill up, but with kernel module debugging, this was
very noticeable.

I suppose I could tell syslog.conf to not use console as well.
-- 
This message posted from opensolaris.org

If you want to test it yourself, I run the following command on domU
''ssh00''

# while [ 1 ]; do logger -p kern.alert `date`; date; sleep 1; done

Which shows output on domU ''ssh'' login as well as on
dom0''s ''virsh console''

dom0:
Apr 27 09:36:02 ssh00.unix lundman: Tue Apr 27 09:36:02 JST 2010
Apr 27 09:36:03 ssh00.unix lundman: Tue Apr 27 09:36:03 JST 2010
domU:
Tue Apr 27 09:36:02 JST 2010
Tue Apr 27 09:36:03 JST 2010

I disconnect "virsh console":

Apr 27 09:36:04 ssh00.unix lundman: Tue Apr 27 09:36:04 JST 2010
xen01:~# 

and domU keeps running:

Tue Apr 27 09:36:05 JST 2010
Tue Apr 27 09:36:06 JST 2010
Tue Apr 27 09:36:07 JST 2010
[...]

until:

Tue Apr 27 09:36:58 JST 2010
Tue Apr 27 09:36:59 JST 2010
Tue Apr 27 09:37:00 JST 2010

and it is dead. You can not even ping the server.

We connect back on "virsh console":

xen01:~# virsh console ssh00.unix
Apr 27 09:36:05 ssh00.unix lundman: Tue Apr 27 09:36:05 JST 2010
Apr 27 09:36:06 ssh00.unix lundman: Tue Apr 27 09:36:06 JST 2010
[...]
Apr 27 09:37:00 ssh00.unix lundman: Tue Apr 27 09:37:00 JST 2010
Apr 27 09:37:27 ssh00.unix lundman: Tue Apr 27 09:37:27 JST 2010

(Bit of a pause there, 27 seconds gone?)

and domU also resumes:

Tue Apr 27 09:37:27 JST 2010
^C
-- 
This message posted from opensolaris.org

On 04/26/10 08:42 PM, Jorgen Lundman wrote:
> If you want to test it yourself, I run the following command on domU
''ssh00''

This is fixed in b137 by
   6931744 DomU occasionally stops responding after reboot
      http://bugs.opensolaris.org/bugdatabase/view_bug.do?bug_id=6931744




MRJ

> # while [ 1 ]; do logger -p kern.alert `date`; date; sleep 1; done
>
> Which shows output on domU ''ssh'' login as well as on
dom0''s ''virsh console''
>
> dom0:
> Apr 27 09:36:02 ssh00.unix lundman: Tue Apr 27 09:36:02 JST 2010
> Apr 27 09:36:03 ssh00.unix lundman: Tue Apr 27 09:36:03 JST 2010
> domU:
> Tue Apr 27 09:36:02 JST 2010
> Tue Apr 27 09:36:03 JST 2010
>
> I disconnect "virsh console":
>
> Apr 27 09:36:04 ssh00.unix lundman: Tue Apr 27 09:36:04 JST 2010
> xen01:~#
>
> and domU keeps running:
>
> Tue Apr 27 09:36:05 JST 2010
> Tue Apr 27 09:36:06 JST 2010
> Tue Apr 27 09:36:07 JST 2010
> [...]
>
> until:
>
> Tue Apr 27 09:36:58 JST 2010
> Tue Apr 27 09:36:59 JST 2010
> Tue Apr 27 09:37:00 JST 2010
>
> and it is dead. You can not even ping the server.
>
> We connect back on "virsh console":
>
> xen01:~# virsh console ssh00.unix
> Apr 27 09:36:05 ssh00.unix lundman: Tue Apr 27 09:36:05 JST 2010
> Apr 27 09:36:06 ssh00.unix lundman: Tue Apr 27 09:36:06 JST 2010
> [...]
> Apr 27 09:37:00 ssh00.unix lundman: Tue Apr 27 09:37:00 JST 2010
> Apr 27 09:37:27 ssh00.unix lundman: Tue Apr 27 09:37:27 JST 2010
>
> (Bit of a pause there, 27 seconds gone?)
>
> and domU also resumes:
>
> Tue Apr 27 09:37:27 JST 2010
> ^C