[Xen-users] Guest lags

[Robert Shaw <robertwilliamshaw@xxxxxxxxx>]

Hi ,

We have a strange problem, we have one xen host machine that seems to be playing up. when we move an image there, and start it it seems fine, but as soon as some IO starts happening on the guest it goes into 100 wait, but there is nothing happening on the host, its like 99 idle. When we moved the guest extracting the same tar.gz file took a minute with the same ram and cpu's where as on the problem host it took 2 and a half hours. I'm not quite sure what information you would require in this situation as there are no errors anywhere that i can find.

Both the host and guest are running CentOS, but the guest is a little behind(5.3 instead of 5.5 for the host). The other difference is that the host is 64 bit and the guest is 32.

The guest resides in an img file.

If we move the guest back to one of our other hosts it works fine.

I have reinstalled the host with a fresh version to no avail, and its fully up to date, but the same problem.

Xen has been installed via yum.

[root@host ~]# rpm -qa | grep xen
kernel-xen-2.6.18-194.8.1.el5
xen-libs-3.0.3-105.el5_5.4
xen-3.0.3-105.el5_5.4

[root@host ~]# cat /etc/redhat-release 
CentOS release 5.5 (Final)

This is the guest config
name = "soe"
uuid = ""
maxmem = 1024
memory = 1024
vcpus = 2
bootloader = "/usr/bin/pygrub"
>>>
vfb = [  ]
disk = [ "tap:aio:/vm/soe.img,xvda,w" ]
vif = [ "mac=,bridge=xenbr0" ]

below are some vmstats(which aren't 100 percent synced, but they look pretty much the same)
on guest
procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
 1 12      0   6272   1440 948340    0    0     0  1832  106  172  0  0  0 100  0
 0 12      0   6644   1440 948340    0    0     0   208  122  177  0  0  0 100  0
 0 12      0   6644   1440 948340    0    0     0     0   62  165  0  0  0 100  0
 0 12      0   6644   1440 948340    0    0     0     0   64  171  0  0  0 100  0
 0 12      0   7268   1444 947968    0    0     0   136 1364  709  4  1  0 95  0
 1 12      0   7268   1444 947956    0    0     0     0   98  168  0  0  0 100  0
 6 12      0   7268   1444 947956    0    0     0     0   64  181  0  0  0 100  0
 6 12      0   6896   1444 947956    0    0     0  1496   70  173  0  0  0 100  0
 0 12      0   6400   1444 947956    0    0     0  1672   86  178  0  0  0 100  0
 0 12      0   6648   1444 947956    0    0     0   824  146  213  0  0  0 100  0
 0 12      0   6696   1444 947956    0    0     0     0   58  165  0  0  0 100  0
 0 12      0   6696   1444 947956    0    0     0     0   81  169  0  0  0 100  0

on host
procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
 0  1    184  13320   5948 2133832    0    0   125   128   38   56  0  0 96  4  0
 0  1    184  13328   5948 2133872    0    0     0   686  426  970  0  0 75 25  0
 0  1    184  13328   5948 2133872    0    0     0   687  405  926  0  0 75 25  0
 1  1    184  13328   5956 2133876    0    0     0   711  434  927  0  0 75 25  0
 0  1    184  13328   5956 2133876    0    0     0   692  471  930  0  0 75 25  0
 0  1    184  13328   5960 2133872    0    0     0   717  408  883  0  0 75 25  0
 0  1    184  13328   5960 2133872    0    0     0   682  411  930  0  0 75 25  0
 1  1    184  13328   5960 2133872    0    0     0   687  402  928  0  0 75 25  0
 0  1    184  13328   5968 2133864    0    0     0   709  405  920  0  0 75 25  0
 0  1    184  14524   5972 2132588    0    0  4100   587 1220 2807  2  0 77 20  0


Any ideas would be appreciated.

Kind Regards,
Rob Shaw
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