Configure VMQ and RSS on physical servers


Samples below are collected from Windows Server 2016

The primary objective is to avoid weighing down Core 0 with networking traffic. This is the first core on the first NUMA node, and this core is responsible for a lot of kernel processing. If this core suffers from contention, a wild blue screen of death will appear. Thus, we want our network adapters to use other cores to process their traffic. We can achieve this in three ways, depending on what we use the adapter for:

  • Enable Receive Side Scaling (RSS) and configure it to use specific cores.
  • Enable Virtual Message Queueing and configure it to use specific cores
  • Set the preferred NUMA node

For physical machines

On network adapters used for generic traffic, we should enable RSS and disable VMQ. On adapters that are part of a virtual switch, we should disable RSS and enable VMQ. The preferred NUMA node should be configured for all physical adapters.

For virtual machines

If the machine has more than one CPU, enable vRSS.

Investigating the NUMA architecture

Sockets and NUMA nodes

Sysinternals coreinfo -s -n will show the relationship between logical processors, sockets and NUMA nodes. In the example below we have a CPU with two sockets and four nodes.


Closest NUMA node

Each PCIE adapter is physically connected to a specific NUMA node. If possible, RSS / VMQ should be mapped to cores on the same NUMA node that the NIC is connected to. Get-NetadApterRss will show you which NUMA node is closest for each adapter. The one in the sample is connected to/closest to NUMA node 0 as the NUMA distance for cores in group 0 is 0. We can also see that the NUMA distance to node 1 for this particular port is lower than the distance to nodes 2 and 3. This is caused by the fact that node 0 and 1 are on the same physical CPU, whereas node 2 and 3 are on another physical CPU.

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Failed to allocate VMQ


Event ID 113 from Hyper-V-VmSwitch is logged each time a VM is started on a host:

Failed to allocate VMQ for NIC [GUID]  (Friendly Name: [VM name]) on switch [GUID](Friendly Name: [Switch name]). Reason – The OID failed. Status = An invalid parameter was passed to a service or function.SNAGHTML37e5e773


This is caused by a bug. Download and install KB3031598 to fix the problem.