:lastproofread: 2025-09-04

.. _vpp_config_dataplane_unix:

.. include:: /_include/need_improvement.txt

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VPP Unix Dataplane Configuration
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The UNIX configuration section is used to control VPP's interaction with the underlying operating system, including operations scheduling.

VPP relies on the polling mechanism to efficiently manage I/O operations and system events. By default VPP continuously polls for events, which leads to permanent 100% CPU usage by all cores assigned to VPP dataplane. This is optimal for performance, but may not be desirable in all environments, especially where power consumption is a concern or where VPP is running inside a hypervisor, especially if VM has burstable thresholds and CPU usage limits.

To mitigate this, VPP provides a configurable polling delay that allows to reduce CPU usage by introducing a delay between polling cycles. This introduces a trade-off between CPU usage and latency, as longer delays can lead to increased latency in processing events.

You can configure the polling delay using the following command in the VyOS CLI:

.. cfgcmd:: set vpp settings unix poll-sleep-usec <delay>

Sets the polling delay in microseconds. A value of 0 means no delay (default), while higher values introduce a delay between polling cycles.

Potential Issues and Troubleshooting
====================================

Setting the polling delay too high can lead to increased latency and reduced performance, as VPP may not respond to events as quickly. Conversely, setting it too low may result in high CPU usage, which can be problematic in resource-constrained environments.

Symptoms of improper configuration may include:

- Increased latency in packet processing
- Higher CPU usage than expected
- Packets lost due to buffer overruns

If you do not need to reduce CPU usage, it is recommended to leave the polling delay at its default value of 0 for optimal performance.

If you need to reduce CPU usage, you may also consider using ``interrupt`` or ``adaptive`` :ref:`DPDK driver modes <vpp_config_dataplane_interface_rx_mode>`, which can provide a balance between performance and resource utilization without affecting polling behavior.