Hyper- V Dynamic Memory - An Illustrated Guide. May 2. 01. 6 by Eric Siron    6    Hyper- V Articles. Even though Hyper- V Dynamic Memory technology has been with us since Service Pack 1 for 2. R2, it remains one of the less discussed, and therefore more poorly understood components of Hyper- V. Despite many claims and common practices to the contrary, Dynamic Memory is perfectly suitable for most production virtualization workloads.

That suitability is a discussion for other articles. This post is intended to explain what Hyper- V Dynamic Memory is, how it functions, and how it compares to memory management techniques in other hypervisors.

As we progress through this post, I’ll use the following screen shot as a reference point: Dynamic Memory Configuration Screen. What is Hyper- V Dynamic Memory? I don’t know of any other virtualization technology that manages memory in a comparable fashion, so if you’re coming to Hyper- V from another hypervisor, you’ll want to pay attention to this part. Most other hypervisors use a different approach to memory management that is more universal, but has problems of its own. Comparison: Oversubscription Model in Other Hypervisors. This is the more common hypervisor memory- management scheme that Hyper- V does not use: Memory Oversubscription Model.

This section contains descriptions of the common bug checks, including the parameters passed to the blue screen.

In this mode, the virtual machine always believes that it has 8 GB of memory to use as it sees fit. In reality, the hypervisor may or may not be silently paging any amount of that memory to disk.

Because of the isolation between the guest operating system and the hypervisor, there’s no way for the host to be certain that it is making the correct choices for what memory to page. Of course, the hypervisor can follow some semantic patterns, such as assuming the guest’s kernel will be in the first few megabytes of memory and skipping that, and it can perform some heuristic analysis and not page memory that it knows the guest is frequently accessing. No matter what, this approach is not without guesswork.

Also, hypervisors that handle memory in this fashion are not bound by the needs of the guests at all. It always has the option to ignore semantics and heuristics, sending active memory to disk in order to make room for the memory needs of other guests.

This can potentially lead to some very heavy disk thrashing and severe performance problems. The primary takeaway from the oversubscription model is that the guest does not know that anything is out of the ordinary and will access its memory as though it were normal physical memory. The secondary takeaway is that performance problems may be caused by memory oversubscription. Hyper- V Dynamic Memory. In contrast to the coercive nature of the memory oversubscription model, Hyper- V Dynamic Memory is cooperative. The hypervisor and its guests work together in memory management. This requires the usage of what is called a balloon driver.

A paging file creates virtual RAM, allowing the OS to “page out” inactive memory and “page in” memory from the file when it is required. This allows the. The wmiprvse.exe process is part of Windows Management Instrumentation of Microsoft. Here are further details of wmiprvse.exe, and whether it might be a virus or spyware. I am monitoring the memory object in Windows 2k8, and am tracking the Page Faults/sec counter. Is there any threshold to determining what is an excessive amount of.

If you’re used to other hypervisors that employ the oversubscription model, you might have heard of this before. Some of them also employ a balloon driver to reduce the need for blind paging. One of the differences is that Hyper- V uses the industry- standard procedure for hot- add memory to grow the virtual machine’s allocation as necessary, then it employs the balloon driver to reclaim memory that the guest is no longer actively using. Using the guest from the screen shot at the start of this post, we’ll work through a normal process. This is what the guest sees when it first boots: Dynamic Memory at Startup. The guest’s memory manager believes that it has a maximum of 5.

Search settings; Web History : Advanced search Language tools. InformationWeek.com: News, analysis and research for business technology professionals, plus peer-to-peer knowledge sharing. Engage with our community. VMware is the global leader in virtualization software, providing desktop and server virtualization products for virtual infrastructure solutions. Even though Hyper-V Dynamic Memory technology has been with us since Service Pack 1 for 2008 R2, it remains one of the less discussed, and therefore more poorly.

Perhaps page faults were more easily understood from the. Hi All, I have a three year old Konica-Minolta magicolor 2450. Typically, the first page sent to the printer after a period of inactivity will have it's contents.

MB of memory to work with because that is its Startup value, so it works to keep its demand below that level. As you can see in the screen shot, this guest does know about the ceiling specified by Dynamic Memory. However, it will behave as though 5. That doesn’t stop applications from requesting more memory, of course.

As they ask for more, the Demand on the memory manager increases — this is called pressure. This is noticed by the Dynamic Memory driver running in the guest, which tells Hyper- V about it.

If Hyper- V has more memory to give, then the Hot Add mechanism kicks in and more is added. If possible, it is assigned with at least enough to cover demand. Our guest now looks like this: Dynamic Memory After Hot Add. The maximum memory in this guest has changed to 8.

MB. If applications place greater demand on memory and there is more to give, the total can increase all the way up to the maximum, which is set at 2. GB. Sometimes, memory needs to be taken away from a guest. That process is quite a bit different. The following illustrates a situation in which that has happened: Dynamic Memory in Action. The above screenshot pair was taken from inside a guest and from its view in Hyper- V Manager, respectively, for a different virtual machine on a host that doesn’t have enough memory to satisfy all of its guests needs simultaneously.

As you can see, the maximum that this guest sees is the same as the maximum memory that has been reserved for it in Dynamic Memory. But, that’s not what’s assigned.

In case the text in the images is too small to read, these are the numbers: The guest operating system’s memory manager reports that it has 1. GB maximum memory. The guest operating system’s memory manager reports that 1. GB of the 1. 5 GB maximum is in use. Hyper- V Manager reports that the guest is currently demanding 9. MB of memory. Hyper- V Manager reports that it has assigned 6.

MB of memory to the guest. The most important thing to remember when you encounter situations like this is that when the memory information displayed in the guest operating system contradicts what is displayed in Hyper- V Manager, Hyper- V Manager is always right. Ultimately, Hyper- V owns all of the physical memory and is only loaning it out to the guests. What they do with it is their business, but they can’t get any more than Hyper- V is willing to provide. So, what’s really going on in this guest?

Why does it appear to have 8. MB more memory than Hyper- V says that it does? The root cause of this behavior lies in the fact that the Hot Add function for memory has no Hot Remove opposite.

Once memory has been added to a guest (or a physical machine using Hot Add memory), that memory must remain assigned until that system is powered down. No matter what happens, the maximum memory as seen by the guest cannot be reduced until it is turned off. That doesn’t mean that Hyper- V can’t take memory from the guest. Can I Play Pirates Of The Caribbean Online With Windows 8 there.

It means that Hyper- V must use its own techniques. Its implementation is the aforementioned balloon driver. There isn’t a built- in tool in 2.

R2 that I know of that can display this information. What you see below is a screen shot taken with RAMMap. Look it over, then check the following paragraph for an explanation of what you see. Dynamic Memory Driver Memory Use“Driver locked” memory is where the memory claimed by the balloon driver lives. Other drivers might also be using some of the memory that you see here, but even RAMMap can’t go any deeper than this. I’m not sure if that’s because Windows prevents it from going further or if it’s just due to the unique behavior of drivers.

Whereas the operating system will reclaim all memory allocated by a user- mode application when it exits even if it was leaking, a driver can completely stop running without releasing its memory. So, there may not be any process tied to this memory that RAMMap or Task Manager can query, but the memory manager knows that it isn’t available. So, where did that 9.

MB of memory go? In truth, Hyper- V has whatever isn’t taken by the other drivers in that guest — which, in this case, is most of it. For this system, Hyper- V has given most of its memory away to other virtual machines. It might also be keeping some for the management operating system. After taking the above screenshot, I turned off another virtual machine on the same host that was consuming 2 GB of RAM. I then refreshed RAMMap, and this is what I saw: Dynamic Memory Deflation.