Disabling VM large page allocations using “monitor_control.disable_mmu_largepages”

Products

• VMware vCenter Server
• VMware vSphere ESXi

Issue/Introduction

This article provides information on disabling large page backing for a VM to get better page sharing using the “monitor_control.disable_mmu_largepages” option in vCenter Server.

Large page allocation for VMs is enabled by default in ESXi because of its benefits to a VM’s workload performance. However, page sharing with large pages does not come into play in until memory is overcommitted. Once memory is overcommitted, large pages are broken down and page sharing kicks in to help reclaim memory as required. This is generally useful except for customer environments that frequently run into states where memory is overcommitted. In such environments, if page sharing was running since system boot up time, it could be very useful in alleviating the pressure on memory resources and it is not ideal to have it kick in only once memory is overcommitted.

Environment

VMware vSphere ESXi 6.7
VMware vSphere ESXi 7.0.0
VMware vCenter Server 7.0.x
VMware vSphere ESXi 6.5

Resolution

In environments where there are likely to overcommit memory, it might be useful to turn off large page backings for a VM completely.

1. Through the vCenter Server, highlight the VM.
2. Navigate to Edit VM settings > VM Options > Advanced > Edit Configuration Parameters > Add Parameter.
3. Add the key value pair:
   
   Key                                            Value
   ------                                         --------
   monitor_control.disable_mmu_largepages         TRUE
    
4. Save the settings.
   
   Note:
   By default, it is set to FALSE which means large page backings for a VM is permitted.
   If this option is set to TRUE, large page allocations will be disallowed for a VM as long as it is up and running and any changes to it will not be effective unless the VM is rebooted. Even if the VM is vMotion-ed to another host, large page backings will continue to be disallowed for this VM.