redsnapper76
Contributor
Contributor

Guest Memory vs Virtual Machine Memory

Hello,

Can someone explain what the difference is between

Guest Memory

Virtual Machine Memory

As you can see in the print screen there is a huge difference between "Guest Memory: Active Guest Memory" and Virtual Machine Memory: VM Consumed.

What is the reason for this?


Thx

0 Kudos
5 Replies
IRIX201110141
Virtuoso
Virtuoso

Amount of memory that is actively used, as estimated by VMkernel based on recently touched memory pages.

Regards,

Joerg

0 Kudos
redsnapper76
Contributor
Contributor

From what I understand:

When we look into the guest OS, the task manager shows +- 2GB used of the 36GB assigned, the rest is free

This equals then the "Active Guest Memory"

The virtual machine memory consumed equals the allocated memory (36GB in this case)

It is correct then to conclude that the Virtual Machine Memory: "VM Consumed equals to allocated memory minus savings by TPS"

VMware Virtual Machine Memory Management

0 Kudos
IRIX201110141
Virtuoso
Virtuoso

No.

Again, active memory is ...... recently touched memory pages....

The docs didnt say in which period of time. Your guest OS showing as used memory everything whats allocated or right in use. Think about when a OS or App using memory for read caching or just allocated resources long time ago but not give the mem free again.

Regards,

Joerg

0 Kudos
redsnapper76
Contributor
Contributor

I still have a question regarding the Virtual Machine Memory: VM Consumed.

We created a vm with 80GB of memory and it run's idle

The VM consumed is then 3-4GB. We then run a memory stress test in the vm going to 100% memory usage.

The VM consumed also goes to 100%, but when we stop the test, the VM consumed remains at 100%

This results then in vRealize Operations that the memory demand & usage remains at 100%

This result that the business week workload tab shows fully red (see vRops forum)

vRealize Operations Forum - VMware {code}

Why is the VM consumed not lowering after x time? Once a vm has demanded 100% usage memory in guest OS, it seems that the host keeps 100% usage .

0 Kudos
sk84
Expert
Expert

There is a small explanation about consumed memory counters in the sdk documentation:

Amount of memory consumed by a virtual machine, host, or cluster.

  • Virtual machine:   Amount of guest physical memory consumed by the virtual machine for guest memory. Consumed memory does not include overhead memory. It includes shared memory and memory that might be reserved, but not actually used. Use this metric for charge-back purposes.

    vm consumed memory = memory granted - memory saved due to memory sharing

Memory Counters

And the consumed memory is an average value and not a real-time value. This means that if you restart the vm and start your stress test and stop it later, the average consumed memory will be displayed higher than it actually is for some time.

--- Regards, Sebastian VCP6.5-DCV // VCP7-CMA // vSAN 2017 Specialist Please mark this answer as 'helpful' or 'correct' if you think your question has been answered correctly.
0 Kudos