WARNING - OLD ARCHIVES

This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-users

[Xen-users] Problem with xen VBDs, xen backend, and dom0 drivers on xen

To: "xen-users@xxxxxxxxxxxxxxxxxxx" <xen-users@xxxxxxxxxxxxxxxxxxx>
Subject: [Xen-users] Problem with xen VBDs, xen backend, and dom0 drivers on xen 4.0+Debian Squeeze
From: Benjamin Weaver <benjamin.weaver@xxxxxxxxxxxxx>
Date: Fri, 11 Nov 2011 15:28:08 +0000
Delivery-date: Fri, 11 Nov 2011 07:29:14 -0800
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
List-help: <mailto:xen-users-request@lists.xensource.com?subject=help>
List-id: Xen user discussion <xen-users.lists.xensource.com>
List-post: <mailto:xen-users@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-users>, <mailto:xen-users-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-users>, <mailto:xen-users-request@lists.xensource.com?subject=unsubscribe>
Sender: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.18) Gecko/20110617 Thunderbird/3.1.11
I am running xen 4.0.1 with debian squeeze (kernel: Linux version 2.6.32-5-xen-amd64 (Debian 2.6.32-38). Below is output indicating the problem.

My vms are Ubuntu (lucid). I cannot save and restore my vms properly. A lucid vm works fine when first created by xm create. But then, when I save (xm save hostname filename), and restore from that file (xm restore filename). I get a vm that lets me login, but then freezes its prompt.

This problem with lucid vms surfaced only a few weeks ago, before which I was running linux-base 2.6.32-35. The problem is related to Bug #644604 (http://lists.debian.org/debian-kernel/2011/10/msg00183.html).

I had gotten some good suggestions on how and whether to compile a kernel version later than Squeeze, but had some difficulties compiling and in any event would like to get a stable release to run my vms.

MY GUESS AT THE PROBLEM: I have since come to suspect a problem of communication between Xen Virtual Block Devices, Xen drivers (frontend and backend) and dom0 drivers that I thought be fixable.

Please confirm if so; any suggestions as to how to fix this problem would be greatly appreciated!


Output (see below)

I notice a couple of things:

1. a.when the lucid vm is created a df command shows only xvda2 showing up as a filesystem; b. an lsmod shows only xen_blkfront and xen_netfront. This is all in contrast to output from the same commands regarding a hardy or lenny vm. In these cases, df shows several active file systems, and lsmod shows several modules, ipv6, jbd, etc., in fact several things except xen_blkfront and xen_netfront.

2. after the lucid vm is saved no reads or writes are being done to its VBDs.



# df command on lenny
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/xvda2             2064208    392684   1566668  21% /
varrun                  262252        28    262224   1% /var/run
varlock                 262252         0    262252   0% /var/lock
udev                    262252        12    262240   1% /dev
devshm                  262252         0    262252   0% /dev/shm
root@lucidxentest3:~#


# df command on lucid
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/xvda2             2064208    545596   1413756  28% /
none                    240380       120    240260   1% /dev
none                    252152         0    252152   0% /dev/shm
none                    252152        28    252124   1% /var/run
none                    252152         0    252152   0% /var/lock
none                    252152         0    252152   0% /lib/init/rw
root@lucidxentest:~#



# lsmod on lucid vm
Module                  Size  Used by
xen_netfront           17890  0
xen_blkfront           10665  2
root@lucidxentest:~#

# lsmod on hardy vm
Module                  Size  Used by
ipv6                  313960  10
evdev                  15360  0
ext3                  149520  1
jbd                    57256  1 ext3
mbcache                11392  1 ext3
root@lucidxentest3:~#


Before xm save, VBDs on lucid vm show read/write activity with non-zero values.


After save, xm top shows lucid vm VBDs with zeroed-out values for read/write. That is, values of 0 under the following columns of xm top output:
VBD_OO   VBD_RD   VBD_WR  VBD_RSECT  VBD_WSECT.




_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users