6.7

Cause
The number of allocatable interrupt vectors scales up with the number of physical CPUs on an ESXi host.
An ESXi host that has 32 CPUs can provide a total of 4096 interrupt vectors. When the host boots,
devices on the host such as storage controllers, physical network adapters, and USB controllers consume
a subset of the 4096 vectors. If these devices require more than 1024 vectors, the maximum number of
potentially supported VFs is reduced.
When a virtual machine powers on and the guest operating system VF driver starts, interrupt vectors are
consumed. If the required number of interrupt vectors is not available, the guest operating system shuts
down unexpectedly without any error messages.
No rule presently exists to determine the number of interrupt vectors consumed or available on a host.
This number depends on the hardware configuration of the host.
Solution
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To be able to power on the virtual machines, reduce the total number of VFs assigned to virtual
machines on the host.
For example, change the SR-IOV network adapter of a virtual machine to an adapter that is
connected to a vSphere Standard Switch or vSphere Distributed Switch.
Remote Direct Memory Access for Virtual Machines
vSphere 6.5 and later releases support remote direct memory access (RDMA) communication between
virtual machines that have paravirtualized RDMA (PVRDMA) network adapters .
Overview of RDMA
RDMA allows direct memory access from the memory of one computer to the memory of another
computer without involving the operating system or CPU . The transfer of memory is offloaded to the
RDMA-capable Host Channel Adapters (HCA) . A PVRDMA network adapter provides remote direct
memory access in a virtual environment.
Using RDMA in vSphere
In vSphere, a virtual machine can use a PVRDMA network adapter to communicate with other virtual
machines that have PVRDMA devices . The virtual machines must be connected to the same vSphere
Distributed Switch.
The PVRDMA device automatically selects the method of communication between the virtual machines .
For virtual machines that run on the same ESXi host with or without a physical RDMA device, the data
transfer is a memcpy between the two virtual machines . The physical RDMA hardware is not used in this
case .
For virtual machines that reside on different ESXi hosts and that have a physical RDMA connection, the
physical RDMA devices must be uplinks on the distributed switch. In this case, the communication
between the virtual machines by way of PVRDMA uses the underlying physical RDMA devices.
vSphere Networking
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