NAME

ena — Driver for the AWS Elastic Network Adapter

SYNOPSIS

/dev/net/ena*

DESCRIPTION

The ena driver is a GLDv3 NIC driver for the AWS Elastic Network Adapter family of virtual devices. The driver supports:

Jumbo frames up to 9216 bytes.
Multiple Rx and Tx rings.

By design, this driver does not support VNICs. A given ENA device can only ever receive traffic for a single unicast MAC address and IP address combination, as determined by the AWS configuration. There is no support for promiscuous mode, or for receiving traffic for additional unicast or multicast addresses.

CONFIGURATION

The ena.conf file contains user configurable parameters, each of which is described below. This file is read when an ENA device is found and an instance of the driver is attached to it. Changes made to this file do not affect running instances. Only instances attached after the changes will see the effects of those changes. Therefore, if you want your change to take effect on a running instance, you must somehow reload it. That could be done by a manual reloading of the driver or a system reboot.

PROPERTIES

The configuration file can be found at /kernel/drv/ena.conf.

rx_queue_num_descs: Minimum: 64 | Maximum: device dependent

Default: device maximum

The rx_queue_num_descs property determines the number of descriptors provided by the Rx queue. Currently a single descriptor is equal to a single packet, but in the future it may be that a single packet consumes multiple descriptors.
rx_queue_intr_limit: Minimum: 16 | Maximum: 4096

Default: 256

The rx_queue_intr_limit property determines the number frames an Rx interrupt will attempt to process before returning and claiming the interrupt. This is meant to keep the ENA Rx interrupt handler from consuming too much system time. In general, when a NIC becomes saturated with packets, the MAC layer will switch the driver into polling mode to reduce interrupt load.
tx_queue_num_descs: Minimum: 64 | Maximum: device dependent

Default: device maximum

The tx_queue_num_descs property determines the number of descriptors provided by the Tx queue. Currently a single descriptor is equal to a single packet, but in the future it may be that a single packet consumes multiple descriptors.

FILES

/kernel/drv/amd64/ena: Device driver (x86)
/kernel/drv/ena.conf: Driver configuration file containing user-configurable options

INTERFACE STABILITY

The tunables in ena.conf are considered Evolving and may change in the future.