Recommended Practices for Windows Guests on OpenStack

Updated

Assumptions

  • Windows version
    • Windows 7 & later
    • Windows Server 2008 R2 & later
  • A KVM hypervisor

General Recommendations

These recommendations are for general Windows performance improvements.

  • Disable the following services:

    • BDESVC
    • wbengine
    • DPS
    • UxSms
    • Defragsvc
    • HomeGroupListener
    • HomeGroupProvider
    • iphlpsvc
    • MSiSCSI
    • swprv
    • CscService
    • SstpSvc
    • wscsvc
    • SSDPSRV
    • SysMain
    • TabletInputService
    • Themes
    • upnphost
    • VSS
    • SDRSVC
    • WinDefend
    • WerSvc
    • MpsSvc
    • ehRecvr
    • ehSched
    • WSearch
    • wuauserv
    • Wlansvc
    • WwanSvc

  • Tweak the registry:

      [HKEY_CLASSES_ROOT\AllFilesystemObjects\shellex\ContextMenuHandlers\Copy To]
  @="{C2FBB630-2971-11D1-A18C-00C04FD75D13}"

  [HKEY_CLASSES_ROOT\AllFilesystemObjects\shellex\ContextMenuHandlers\Move To]
  @="{C2FBB631-2971-11D1-A18C-00C04FD75D13}"

  [HKEY_CURRENT_USER\Control Panel\Desktop]
  "AutoEndTasks"="1"
  "HungAppTimeout"="1000"
  "MenuShowDelay"="8"
  "WaitToKillAppTimeout"="2000"
  "LowLevelHooksTimeout"="1000"

  [HKEY_CURRENT_USER\Control Panel\Mouse]
  "MouseHoverTime"="8"

  [HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
  "NoLowDiskSpaceChecks"=dword:00000001
  "LinkResolveIgnoreLinkInfo"=dword:00000001
  "NoResolveSearch"=dword:00000001

  • In any cloud environment with many Microsoft Windows based virtual machines, use a Windows Key Management Service.

    • Only active machines consume a license (instead of statically assigning).
    • It is easier to track the actual number of Windows licenses in use.
    • It makes virtual machine deployment much easier.

CPU Performance

  • Try to fit a Windows guest into a numa node.
  • In the host BIOS, make sure power management is set to OS control or custom. This allows OS control by using tuned virtual-host on the host.
  • Set the Power Options to the high performance power plan.
  • Enable hyper-threading.

Disk Performance

  • Install the VirtIO disk class driver.

  • Modify the XML file to specify the VirtIO device model, and install VirtIO drivers in the guest.

  • Use raw or QCOW2 disk image file formats.

  • Use pre-allocated raw disk image files. QCOW images cannot be pre-allocated, so this only applies to raw.

  • With QCOW2, preallocating your metadata space will hugely improve performance. This must be performed at the command line:

      qemu-img create -f qcow2 -o size=10000000000,preallocation=metadata file.img

  • Disable KVM disk caching; allow Windows file system caches to handle this.

  • Disable write-back caching; write-back caching will decrease performance. Write-through caching also affects performance, but not as badly.

Memory Performance

  1. Enable Huge pages on the compute node. HugePage memory is locked and cannot be swapped out. To set Huge pages in host:

     echo 15000  > /proc/sys/vm/nr_hugepages
 cat /proc/meminfo | grep Huge
 mount -t hugetlbfs hugetlbfs /dev/hugepages

  2. Restart libvirt after you mount huge pages:

     service libvirtd restart

  3. Enable Kernel Same-page merging module. This allows identical memory pages to be shared amongst virtualized guests and for over provisioning.

  4. Reset the virtual memory setting. Make it static, meaning the initial size and max size are the same. Set this large enough to represent your expected workload.

    1. In the Control Panel, open Advanced System settings.
    2. Click the Advanced tab and select Performance -> Settings -> Advanced -> Virtual memory.
    3. Disable Automatically manage paging file....
    4. Select Custom size.
    5. Set the initial size and maximum size.

General Networking

  • Match MTU size with underlying network infrastructure.

  • Install the VirtIO network driver.

  • Disable Windows scaling heuristics.

  • Enable compound TCP.

  • Disable TCP auto-tuning.

      netsh int tcp set global autotuninglevel=disabled

  • Some systems (though not all) can benefit from some additional network tunning for TCP/IP performance.

      REGISTRY KEYS

  Subkey: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\TCPIP\Parameters

  Value Name					Value (decimal)

  TcpTimedWaitDelay   		30
  MaxUserPort					32768	  #minimum
  TcpMaxDataRetransmissions	5		  #seconds
  TcpNumConnections			16777214

  Subkey: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\AFD\Parameters 

  EnableDynamicBacklog		00000001
  MinimumDynamicBacklog		00000020
  MaximumDynamicBacklog	 	00001000
  DynamicBacklogGrowthDelta 	00000010
  KeepAliveInterval			1			#seconds

  Subkey: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\{Interface GUID}*
  * {Interface GUID} is different for every system.

  TcpNoDelay					1
  TcpAckFrequency 			1

P2V Issues

  • Run sysprep after firstboot.
  • Using Device Manager, show hidden devices, and uninstall any unused devices.

libvirt Tuning

The libvirt process uses an XML configuration file, located at /var/lib/nova/instances/{UUID}/libvirt.xml.

Editing the exact Windows instance requires knowing the UUID of the virtual machine.
To find virtual machine UUID:

  1. Get list of running VMs on compute node:

     virsh list

  2. From the list of running VMs, select the domain ID you're interested in.

     virsh dumpxml {domain ID} | grep '<uuid>'

There are several changes that can improve performance:

  • Enabing memory backing
  • Changing vcpu to pcpu pinning
  • Using numatune
  • Setting the correct model type
  • Setting the cache mode to none
  • Setting the I/O mode to native
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