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JUNE 7-10, 2010 | NEW ORLEANS, LA
Hyper-V and Dynamic Memory in DepthBenjamin ArmstrongSenior Program Manager LeadMicrosoft Corporation
SESSION CODE: VIR304
AgendaUsers, Memory & VirtualizationDynamic Memory
Architecture & ConceptsSystem Impact
Memory Techniques / Competition
Users, Memory & Virtualization
No one can size VMsHow much memory does an IIS server actually need?Print server?File server?Branch Cache?Direct Access?How much will performance be affected if you halved the amount of memory in a VM?
No one wants to size VMs“New virtual machines get 1GB of RAM [no matter what the VM is running]. I only give people more memory if they complain about performance”
“All VMs get 4GB of RAM [I have no idea what is happening with that memory] and no one complains”
“I take the minimum system requirements and add (insert one: 50%, 100%, 150%)”
“A vendor tells me their app needs 4GB of RAM. I do not have the time to test this to find out if it is true or not”
Virtualization & MemoryMemory
Key factor to the number of running VMsPossibly most expensive asset in system
Customer RequirementsMaximum density, without sacrificing performanceMaintain consistent performanceDon’t provide a feature that’s unsuitable for production use
Hyper-V R2 SP1Dynamic Memory
Dynamic Memory GoalsHigher VM consolidation ratios with minimal performance impact
Dependent on:How much variation in memory utilization the workloads haveHow good a job you did of sizing the systems in the first place
Work well for both server and desktop workloadsAdd minimal overhead to the systemPass the “that looks right” test
Adding/Removing MemoryAdding Memory
Enlightened fashionSynthetic Memory Driver (VSP/VSC Pair)
No hardware emulationLight weight
Removing MemoryWanted to remove memoryBallooning is more efficient
Messes up task manager in the guest OS
System RequirementsParent Requirements:
Windows Server 2008 R2 SP1Microsoft Hyper-V Server 2008 R2 SP1
Windows Server 2003, 2008 & 2008 R232-bit & 64-bit versions
Windows Vista and Windows 7Enterprise and Ultimate Editions only32-bit & 64-bit versions
Dynamic Memory Architecture & Concepts
Dynamic Memory Architecture
Windows Kernel
Guest Applications
VMBus
Hypervisor
VMMS
OSMicrosoft Hyper-V
User Mode
KernelMode
Provided by:
VMBus
VMWP
VID
Memory Balancer
Memory Balancer Interface
GMOMemory Manager
DM VDEV/VSP
DM VSC
Dynamic Memory Components
Windows Kernel
Example0 512 MB
Hot-add
1024MB
Hot-add
VM Memory
Ballooned MemoryVM Memory
Second VM MemoryParent Memory
Startup & MaxStartup: amount of memory to boot VM
BIOS does not know about DMGuest OS may not know about DMDefault: 512MB
Max: don’t let the VM above this amountDefault: 64GB
Availability & PriorityAvailability is a concept
How much memory does the VM have?How much memory does the VM want?The difference is the availability
Priority: which VM gets the memory first1-10,000: default is 5,000The higher the priority, the higher the availability
Memory BufferHow much “free” memory should we try and keep in the VM?
Allows for responsiveness to bursty workloadsCan be used for file cache
“I like to configure my virtual machines so that they have ~20% free memory”
Dynamic MemoryBenjamin ArmstrongSenior Program Manager LeadMicrosoft
DEMO
System Impact
Changes to Root ReserveHyper-V has always had the concept of a reserve of memory that is kept for the parent partitionDM allows VMs to push up against the reserve consistentlyNew behavior to better protect the parent partition from rampaging virtual machines
New registry key in placeAllows you to reserve static memory for the parent partition
May result in less memory being available for VMs
Changes to NUMA management…Wait – what is NUMA?Why do I care?How does this work today?
What is “NUMA”?A traditional computer:
Computer
CPU CPU CPU CPU
BUS
Memory
VM VM VM VM
VM VM VM VM
What is “NUMA”?A NUMA computer:
Computer
CPU CPU CPU CPU
BUS
Memory
VM VM VM VM
VM VM VM VM
Back Channel
Memory
BUS
Node 1 Node 2
Why do I care?VM memory should come from the “local NUMA node”
Computer
CPU CPU CPU CPU
BUS
Memory
VM VM VM VM
VM VM VM VM
Back Channel
Memory
BUS
Node 1 Node 2
Good!
Why do I care?VM memory should come from the “local NUMA node”
Computer
CPU CPU CPU CPU
BUS
Memory
VM VM VM VM
VM VM VM VM
Back Channel
Memory
BUS
Node 1 Node 2
Bad
How does this work today?Hyper-V tries to get all memory for a virtual machine from a single NUMA nodeWhen it cannot – the virtual machine “spans” NUMA nodesUsers can set preferred NUMA nodes for virtual machines in order to get the best distribution
Changes to NUMA managementDynamic memory can result in more virtual machines spanning NUMA nodes
A virtual machine might start all on one node – but added memory might come from another node
New option to disable NUMA node spanning
Disabling NUMA SpanningMakes the system behave like multiple small computers
Computer
CPU CPU CPU CPU
BUS
Memory
VM VM VM VM
VM VM VM VM
Back Channel
Memory
BUS
Node 1 Node 2
Memory Techniques / Competition
Understanding philosophical differencesMicrosoft
Understands what guest information to useBuilding on top of guest OS knowledge
Trying to get the “best bang for buck” in virtual memory managementVMware
Does not trust guest informationBuilding a “black box” solution
Started with memory swapping, and digging out of the hole
Dynamic Memory, not OvercommitOverloaded Term
Page SharingSecond Level PagingBalloon Type Mechanisms
No one wants to overcommit their resourceYou don’t overcommit other resources (really – you do not)VMware does not want you to overcommit memory (really)
DM treats memory like we treat CPU resourcesDynamically schedulable resource
External Page SharingHow it works:1. Hash all memory and store it in a table…2. Identify the common hashes and then…3. Perform a bit by bit comparison
What VMware doesn’t tell you…Page Sharing not dynamicCan take hours to share pagesThe largest benefit are zero pagesDoesn’t work with large pages
Second Level PagingMany problems:
Swapping Guest Kernel ResourcesDouble PagingDisks are slow
But it always works…
Other TechniquesGuest directed page sharingMemory compressionAnd on…
We will continue to invest here and work on identifying the best techniques for customer work loads
What next?
Test the beta – and talk to us!Try Dynamic Memory out – for both server and desktop environments
Let us know how DM is working for youLet us know if you think we have something wrong
Track Resources
Virtualization @ Microsoft: http://www.microsoft.com/virtualization
Hyper-V on TechNet: http://technet.microsoft.com/library/cc753637(WS.10).aspx
Virtualization Team Blog: http://blogs.technet.com/b/virtualization/
Virtual PC Guy: http://blogs.msdn.com/b/virtual_pc_guy
Resources
www.microsoft.com/teched
Sessions On-Demand & Community Microsoft Certification & Training Resources
Resources for IT Professionals Resources for Developers
www.microsoft.com/learning
http://microsoft.com/technet http://microsoft.com/msdn
Learning
Related Content
Breakout Sessions: VIR402- Virtualization FAQ, Tips, and Tricks
Interactive Sessions: VIR09-INT – Virtualization Round Table Discussion
Hands-on Labs: VIR04-HOL – Config and Managing Windows Server 2008 R2 Hyper-V VIR07-HOL – Introduction to Windows Server 2008 R2 Hyper-V
Product Demo Stations: TLC-35 – Server Virtualization
Complete an evaluation on CommNet and enter to win!
© 2010 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to
be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.
