OpenNebula

The following was reported by Marcos Dias de Assuncao, in the mailing list

We noticed that after rebooting the hosts' free memory informed by >the xen probe seemed a little strange. Then we started OpenNebula >with no hosts and added two hosts again (i.e. gieseking and >billabong), each with 2GB of RAM and a few MBs reserved to dom0 in
xend-config.sxp. The command 'onehost list' reported:

  HID NAME        RVM   TCPU   FCPU   ACPU    TMEM     FMEM STAT
    0 gieseking     0    200    196    200 2094080   129024   on
    1 billabong     0    200    200    200 2094080   129024   on

We submitted a request whose template is:

NAME     = susebox
CPU      = 1
MEMORY   = 256
OS       = [kernel="/boot/vmlinuz-2.6.25.18-0.2-xen",initrd="/boot/ 
initrd-2.6.25.18-0.2-xen",kernel_cmd="rw",root="hda1"]
DISK     = [source="/home/oneadmin/vm/domains/opensuse11/ 
[[OpenSuse]]11.img",target="hda1",readonly="no", clone="no"]
NIC      = [mac="00:16:3e:01:01:01"]
#GRAPHICS = [type="vnc",listen="127.0.0.1",port="5900"]

and of course, 'onevm list' reported the VM as pending because the
hosts did not have enough memory:

   ID     NAME STAT CPU     MEM        HOSTNAME        TIME
    6  susebox pend   0       0                 00 00:02:19

We found that the xen probe (ONE_LOCATION/lib/im_probes/xen.rb) >uses 'sudo xm info' to obtain information about the host. The >command on billabong reveals:

total_memory           : 2045
free_memory            : 126
max_free_memory        : 1678
max_para_memory        : 1674
max_hvm_memory         : 1662

If I start the same VM directly on the host, xm will create the
domain. The command 'xm info' shows the following during the VM's
execution:

free_memory            : 1
max_free_memory        : 1422
max_para_memory        : 1418
max_hvm_memory         : 1406

A new run of 'sudo xm info' on billabong after the VM is shut down
shows:

total_memory           : 2045
free_memory            : 257
max_free_memory        : 1678
max_para_memory        : 1674
max_hvm_memory         : 1662

And 'onehost list' now shows the updated information:

  HID NAME           RVM   TCPU   FCPU   ACPU    TMEM     FMEM STAT
    0 gieseking        0    200    191    200 2094080   129024   on
    1 billabong        0    200    200    200 2094080   263168   on

The reason for the change in free_memory is that dom0 will balloon
out when needed to free memory for domUs. We believe that the probe
should report max_free_memory. This way, we changed the following
lines of ONE_LOCATION/lib/im_probes/xen.rb:

when 'free_memory'
         memory_info[:free]=columnsr1.to_i*1024

to:

when 'max_free_memory'
         memory_info[:free]=columnsr1.to_i*1024