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WM(4) Device Drivers Manual WM(4)

wm — Intel i8254x Gigabit Ethernet driver

wm* at pci? dev ? function ?


options WM_RX_PROCESS_LIMIT_DEFAULT
options WM_RX_INTR_PROCESS_LIMIT_DEFAULT

Configuration of PHYs may also be necessary. See mii(4).

The wm device driver supports Gigabit Ethernet interfaces based on the Intel i8254x family of Gigabit Ethernet chips. The interfaces supported by the wm driver include:

In addition to Intel's own “PRO/1000” line of Gigabit Ethernet interfaces, these chips also appear on some server systems, processor evaluation boards, and in embedded systems.

The i825[478]x supports IPv4/TCP/UDP checksumming and TCP segmentation in hardware. The wm driver supports these features of the chip. See ifconfig(8) for information on how to enable this feature.

Many chips supported by the wm driver support jumbo frames, however several chips do not support jumbo frames, e.g. i82542, i82081H and 82567V. Jumbo frames can be configured via the interface MTU setting. Selecting an MTU larger than 1500 bytes with the ifconfig(8) utility configures the adapter to receive and transmit jumbo frames.

The maximum number of received packets processed in each softint(9) context. This option only affects multiqueue. The value range is from zero to UINT_MAX. The default value is 100. When you increase this value, both the receive latency and the receive throughput will increase.
Transmit side of WM_RX_PROCESS_LIMIT_DEFAULT.
The maximum number of received packets processed in each hardware interrupt context. This option only affects multiqueue. The value range is from zero to UINT_MAX. The default value is 0. When you increase this value, both the receive latency and the receive throughput will decrease.
Transmit side of WM_RX_INTR_PROCESS_LIMIT_DEFAULT.
Enable many event counters such as each Tx drop counter and Rx interrupt counter. Caution: If this flag is enabled, the number of evcnt entries increase very much.
If this option is set non-zero value, this driver does not use msi. The default value is 0.
If this option is set non-zero value, this driver does not use msix. The default value is 0.

Setting WM_RX_INTR_PROCESS_LIMIT_DEFAULT to zero means so-called polling mode, that is, once an interrupt occurs, the driver keep processing received packets until WM_RX_PROCESS_LIMIT_DEFAULT. Polling mode increases latency a little, however it suppresses performance degradation at high load very well.

If you want to disable polling mode (to use traditional interrupt driven mode), you should set WM_RX_PROCESS_LIMIT_DEFAULT to zero and set WM_RX_INTR_PROCESS_LIMIT_DEFAULT to UINT_MAX.

arp(4), ifmedia(4), mii(4), netintro(4), pci(4), ifconfig(8)

The wm driver first appeared in NetBSD 1.6.

The wm driver was written by Jason R. Thorpe <thorpej@wasabisystems.com>.

EEE (Energy Efficiency Ethernet) is not currently supported.

April 13, 2018 NetBSD-9.2