[PVE-User] KSM, SWAP and Overcommitting

Laurent LEGENDRE geminux50 at gmail.com
Thu Sep 27 11:49:57 CEST 2012


Hello,

I have some questions about KSM and SWAP.
We run 13 vm with debian6. Most of them run at least a LAMP server plus
eventually some other services (ldap, nagios, postfix...)
12GB of ram is allocated for VMs. 30GB are used over 32GB available because
of buffered and cached memory. So proxmox start swapping...
KSM is running but does not seems doing its job...pages_sharing is always
at 0
I think it should shared some pages, all virtualized OSes are similar and
runs similar services

Is that normal? How to get KSM working?
Should I disable swap on proxmox (swappiness=0)
Can you give other advices and best practises about memory management and
overcommitting ?

Thanks !

# qm list
      VMID NAME     STATUS   MEM(MB)  BOOTDISK(GB)  PID
       101 debian6 running    1024      10.00       184793
       102 debian6 running    1024      10.00       3155
       103 freebsd running    512       4.00        220229
       104 debian6 running    1024      50.00       3132
       105 debian6 running    256       2.00        145917
       106 debian6 running    2048      100.00      147030
       107 debian6 running    1024      20.00       6616
       108 debian6 running    2048      5.00        222889
       109 debian6 running    256       5.00        7042
       110 debian6 running    512       8.00        8388
       111 debian6 running    256       5.00        8443
       112 debian6 running    2048      300.00      152936
       114 debian6 running    256       4.00        8552
       116 debian6 running    512       5.00        8795

# free -m
             total   used    free    shared  buffers  cached
Mem:         32172   30455    1716   0       394      17410
-/+ buffers/cache:   12650    19521
Swap:         1027   794      232

# cat /sys/kernel/mm/ksm/pages_sharing
0

# grep KSM /boot/config-`uname -r`
CONFIG_KSM=y

# /etc/init.d/ksmtuned status
KSM control daemon is running..

# pveversion -v
pve-manager: 1.9-26 (pve-manager/1.9/6567)
running kernel: 2.6.32-6-pve
proxmox-ve-2.6.32: 1.9-55+ovzfix-2
pve-kernel-2.6.32-6-pve: 2.6.32-55+ovzfix-1
pve-kernel-2.6.32-7-pve: 2.6.32-55+ovzfix-2
qemu-server: 1.1-32
pve-firmware: 1.0-15
libpve-storage-perl: 1.0-19
vncterm: 0.9-2
vzctl: 3.0.29-3pve1
vzdump: 1.2-16
vzprocps: 2.0.11-2
vzquota: 3.0.11-1dso1
pve-qemu-kvm: 0.15.0-2
ksm-control-daemon: 1.0-6
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