Virtual machine becomes unresponsive due to host memory exhaustion

Products

• VMware vSphere ESXi

Issue/Introduction

One or more virtual machines on the host becomes unresponsive. Services that would ordinarily be running within the guest, fails to start.
The hosts' physical memory may have been reserved to the maximum available by the virtual machines.

Environment

VMware vSphere 7.0
VMware vSphere 8.0

Cause

Logs report host is out of memory: 

VMKwarning.log:
2025-01-29T12:17:36.816Z cpu89:2099469)WARNING: ScsiPath: 2530: Out of Memory
2025-01-29T12:17:36.816Z cpu89:2099469)WARNING: ScsiPath: 2530: Out of Memory
2025-01-29T12:17:36.818Z cpu247:2098616)WARNING: VisorFSRam: 213: Cannot extend visorfs file /tmp/_osdata####_mwr/log/vmkernel.log because memory could not be allocated for its ramdisk (osdata).
2025-01-29T12:17:36.820Z cpu247:2098616)WARNING: VisorFSRam: 213: Cannot extend visorfs file /var/log/.vmsyslogd.err because memory could not be allocated for its ramdisk (var).

VMkernel.log:
2025-01-29T06:11:46.470Z cpu155:99113780)uw.99113781 (865339591) extraMin/extraFromParent: 64/64, host (0) childEmin/eMinLimit: 268262757/268262781     =======>  64 pages of memory was requested but host has only 24 pages available (268262781 - 268262757).
2025-01-29T06:11:46.470Z cpu155:99113780)Admission failure in path: host:vim:vmvisor:esximage:python.99113781:uw.99113781

2025-01-29T12:17:36.816Z cpu89:2099469)Admission failure in path: host:system:storage:ScsiStorage
2025-01-29T12:17:36.816Z cpu89:2099469)ScsiStorage (167) extraMin/extraFromParent: 1/1, host (0) childEmin/eMinLimit: 268262781/268262781
2025-01-29T12:17:36.816Z cpu89:2099469)WARNING: ScsiPath: 2530: Out of Memory


The error in the VMKernel.log indicates that the VMkernel attempted to reserve memory and none was available.
This can happen when virtual machines with reserved memory are utilizing all available resources on the host and the memory requirements of the VMKernel increased during operation. 
 
To view the the unreserved memory at a point in time using ESXTOP, hit option 'm' for memory panel and view the header pane. For definitions, refer to Using esxtop - Memory Panel.

Resolution

Reduce the reserved memory of virtual machines on the host to allow ESXi to manage both virtual machine and VMKernel requirements.