Adjust RSS CPU Allocation Using Regedit

Receive Side Scaling (RSS) optimizes network performance by distributing incoming network traffic processing across multiple CPU cores to prevent a single processor from becoming a bottleneck. While these parameters can often be adjusted via device properties or PowerShell, configuring them through the Windows Registry Editor (Regedit) provides a direct way to enforce specific processor assignments. This guide walks you through locating your network adapter’s registry entry and modifying the relevant RSS processor allocation keys.

Step 1: Open the Registry Editor

1. Press Win + R to open the Run dialog box.
2. Type regedit and press Enter or click OK.
3. Select Yes if prompted by User Account Control (UAC).

Step 2: Navigate to the Network Adapters Registry Key

In the Registry Editor address bar, navigate to the following path:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4d36e972-e325-11ce-bfc1-08002be10318}

This key contains numbered subfolders (such as 0000, 0001, 0002) representing the network interfaces installed on your system.

Step 3: Identify Your Target Network Adapter

1. Click through the numbered subkeys (0000, 0001, etc.).
2. In the right pane, locate the DriverDesc string value.
3. Verify that the value data matches the exact name of the network adapter you wish to configure (for example, Intel(R) Ethernet Connection I219-V or Mellanox ConnectX).

Step 4: Adjust the RSS CPU Allocation Registry Values

Once inside the correct numbered subkey, look for the following DWORD (32-bit) values. If they do not exist, right-click an empty area in the right-hand pane, select New > DWORD (32-bit) Value, and name them accordingly:

• *RssBaseProcNumber: Defines the lowest CPU core index assigned to RSS.
  • Double-click the value, switch the base to Decimal, and enter the core number where RSS processing should begin (e.g., 0 for the first core, 1 to avoid CPU 0, etc.).
• *MaxRssProcessors: Defines the maximum number of logical processors used for RSS.
  • Double-click the value, switch the base to Decimal, and enter the desired number of cores (commonly powers of 2, such as 2, 4, 8, or 16).
• *NumaNodeId (Optional): Specifies the preferred NUMA node for RSS processing on multi-socket systems. Set this to the appropriate node number if applicable.

Step 5: Apply the Changes

1. Close the Registry Editor.
2. Disable and re-enable your network adapter in the Network Connections panel (ncpa.cpl), or restart your computer to apply the new configuration.

Step 6: Verify the Configuration

To confirm that the registry changes have taken effect, open Windows PowerShell as Administrator and run:

Get-NetAdapterRss

Inspect the output to confirm that BaseProcessorGroup, BaseProcessorNumber, and MaxProcessors reflect the values you entered in the registry.