Documentation/networking/e1000.rst

.. SPDX-License-Identifier: GPL-2.0+

Linux* Base Driver for Intel(R) Ethernet Network Connection
===========================================================

Intel Gigabit Linux driver.
Copyright(c) 1999 - 2013 Intel Corporation.

Contents
========

- Identifying Your Adapter
- Command Line Parameters
- Speed and Duplex Configuration
- Additional Configurations
- Support

Identifying Your Adapter
========================

For more information on how to identify your adapter, go to the Adapter &
Driver ID Guide at:

    http://support.intel.com/support/go/network/adapter/idguide.htm

For the latest Intel network drivers for Linux, refer to the following
website.  In the search field, enter your adapter name or type, or use the
networking link on the left to search for your adapter:

    http://support.intel.com/support/go/network/adapter/home.htm

Command Line Parameters
=======================

The default value for each parameter is generally the recommended setting,
unless otherwise noted.

NOTES:
	For more information about the AutoNeg, Duplex, and Speed
        parameters, see the "Speed and Duplex Configuration" section in
        this document.

        For more information about the InterruptThrottleRate,
        RxIntDelay, TxIntDelay, RxAbsIntDelay, and TxAbsIntDelay
        parameters, see the application note at:
        http://www.intel.com/design/network/applnots/ap450.htm

AutoNeg
-------

(Supported only on adapters with copper connections)

:Valid Range:   0x01-0x0F, 0x20-0x2F
:Default Value: 0x2F

This parameter is a bit-mask that specifies the speed and duplex settings
advertised by the adapter.  When this parameter is used, the Speed and
Duplex parameters must not be specified.

NOTE:
       Refer to the Speed and Duplex section of this readme for more
       information on the AutoNeg parameter.

Duplex
------

(Supported only on adapters with copper connections)

:Valid Range:   0-2 (0=auto-negotiate, 1=half, 2=full)
:Default Value: 0

This defines the direction in which data is allowed to flow.  Can be
either one or two-directional.  If both Duplex and the link partner are
set to auto-negotiate, the board auto-detects the correct duplex.  If the
link partner is forced (either full or half), Duplex defaults to half-
duplex.

FlowControl
-----------

:Valid Range:   0-3 (0=none, 1=Rx only, 2=Tx only, 3=Rx&Tx)
:Default Value: Reads flow control settings from the EEPROM

This parameter controls the automatic generation(Tx) and response(Rx)
to Ethernet PAUSE frames.

InterruptThrottleRate
---------------------

(not supported on Intel(R) 82542, 82543 or 82544-based adapters)

:Valid Range:
   0,1,3,4,100-100000 (0=off, 1=dynamic, 3=dynamic conservative,
   4=simplified balancing)
:Default Value: 3

The driver can limit the amount of interrupts per second that the adapter
will generate for incoming packets. It does this by writing a value to the
adapter that is based on the maximum amount of interrupts that the adapter
will generate per second.

Setting InterruptThrottleRate to a value greater or equal to 100
will program the adapter to send out a maximum of that many interrupts
per second, even if more packets have come in. This reduces interrupt
load on the system and can lower CPU utilization under heavy load,
but will increase latency as packets are not processed as quickly.

The default behaviour of the driver previously assumed a static
InterruptThrottleRate value of 8000, providing a good fallback value for
all traffic types,but lacking in small packet performance and latency.
The hardware can handle many more small packets per second however, and
for this reason an adaptive interrupt moderation algorithm was implemented.

Since 7.3.x, the driver has two adaptive modes (setting 1 or 3) in which
it dynamically adjusts the InterruptThrottleRate value based on the traffic
that it receives. After determining the type of incoming traffic in the last
timeframe, it will adjust the InterruptThrottleRate to an appropriate value
for that traffic.

The algorithm classifies the incoming traffic every interval into
classes.  Once the class is determined, the InterruptThrottleRate value is
adjusted to suit that traffic type the best. There are three classes defined:
"Bulk traffic", for large amounts of packets of normal size; "Low latency",
for small amounts of traffic and/or a significant percentage of small
packets; and "Lowest latency", for almost completely small packets or
minimal traffic.

In dynamic conservative mode, the InterruptThrottleRate value is set to 4000
for traffic that falls in class "Bulk traffic". If traffic falls in the "Low
latency" or "Lowest latency" class, the InterruptThrottleRate is increased
stepwise to 20000. This default mode is suitable for most applications.

For situations where low latency is vital such as cluster or
grid computing, the algorithm can reduce latency even more when
InterruptThrottleRate is set to mode 1. In this mode, which operates
the same as mode 3, the InterruptThrottleRate will be increased stepwise to
70000 for traffic in class "Lowest latency".

In simplified mode the interrupt rate is based on the ratio of TX and
RX traffic.  If the bytes per second rate is approximately equal, the
interrupt rate will drop as low as 2000 interrupts per second.  If the
traffic is mostly transmit or mostly receive, the interrupt rate could
be as high as 8000.

Setting InterruptThrottleRate to 0 turns off any interrupt moderation
and may improve small packet latency, but is generally not suitable
for bulk throughput traffic.

NOTE:
       InterruptThrottleRate takes precedence over the TxAbsIntDelay and
       RxAbsIntDelay parameters.  In other words, minimizing the receive
       and/or transmit absolute delays does not force the controller to
       generate more interrupts than what the Interrupt Throttle Rate
       allows.

CAUTION:
          If you are using the Intel(R) PRO/1000 CT Network Connection
          (controller 82547), setting InterruptThrottleRate to a value
          greater than 75,000, may hang (stop transmitting) adapters
          under certain network conditions.  If this occurs a NETDEV
          WATCHDOG message is logged in the system event log.  In
          addition, the controller is automatically reset, restoring
          the network connection.  To eliminate the potential for the
          hang, ensure that InterruptThrottleRate is set no greater
          than 75,000 and is not set to 0.

NOTE:
       When e1000 is loaded with default settings and multiple adapters
       are in use simultaneously, the CPU utilization may increase non-
       linearly.  In order to limit the CPU utilization without impacting
       the overall throughput, we recommend that you load the driver as
       follows::

           modprobe e1000 InterruptThrottleRate=3000,3000,3000

       This sets the InterruptThrottleRate to 3000 interrupts/sec for
       the first, second, and third instances of the driver.  The range
       of 2000 to 3000 interrupts per second works on a majority of
       systems and is a good starting point, but the optimal value will
       be platform-specific.  If CPU utilization is not a concern, use
       RX_POLLING (NAPI) and default driver settings.

RxDescriptors
-------------

:Valid Range:
 - 48-256 for 82542 and 82543-based adapters
 - 48-4096 for all other supported adapters
:Default Value: 256

This value specifies the number of receive buffer descriptors allocated
by the driver.  Increasing this value allows the driver to buffer more
incoming packets, at the expense of increased system memory utilization.

Each descriptor is 16 bytes.  A receive buffer is also allocated for each
descriptor and can be either 2048, 4096, 8192, or 16384 bytes, depending
on the MTU setting. The maximum MTU size is 16110.

NOTE:
       MTU designates the frame size.  It only needs to be set for Jumbo
       Frames.  Depending on the available system resources, the request
       for a higher number of receive descriptors may be denied.  In this
       case, use a lower number.

RxIntDelay
----------

:Valid Range:   0-65535 (0=off)
:Default Value: 0

This value delays the generation of receive interrupts in units of 1.024
microseconds.  Receive interrupt reduction can improve CPU efficiency if
properly tuned for specific network traffic.  Increasing this value adds
extra latency to frame reception and can end up decreasing the throughput
of TCP traffic.  If the system is reporting dropped receives, this value
may be set too high, causing the driver to run out of available receive
descriptors.

CAUTION:
          When setting RxIntDelay to a value other than 0, adapters may
          hang (stop transmitting) under certain network conditions.  If
          this occurs a NETDEV WATCHDOG message is logged in the system
          event log.  In addition, the controller is automatically reset,
          restoring the network connection.  To eliminate the potential
          for the hang ensure that RxIntDelay is set to 0.

RxAbsIntDelay
-------------

(This parameter is supported only on 82540, 82545 and later adapters.)

:Valid Range:   0-65535 (0=off)
:Default Value: 128

This value, in units of 1.024 microseconds, limits the delay in which a
receive interrupt is generated.  Useful only if RxIntDelay is non-zero,
this value ensures that an interrupt is generated after the initial
packet is received within the set amount of time.  Proper tuning,
along with RxIntDelay, may improve traffic throughput in specific network
conditions.

Speed
-----

(This parameter is supported only on adapters with copper connections.)

:Valid Settings: 0, 10, 100, 1000
:Default Value:  0 (auto-negotiate at all supported speeds)

Speed forces the line speed to the specified value in megabits per second
(Mbps).  If this parameter is not specified or is set to 0 and the link
partner is set to auto-negotiate, the board will auto-detect the correct
speed.  Duplex should also be set when Speed is set to either 10 or 100.

TxDescriptors
-------------

:Valid Range:
  - 48-256 for 82542 and 82543-based adapters
  - 48-4096 for all other supported adapters
:Default Value: 256

This value is the number of transmit descriptors allocated by the driver.
Increasing this value allows the driver to queue more transmits.  Each
descriptor is 16 bytes.

NOTE:
       Depending on the available system resources, the request for a
       higher number of transmit descriptors may be denied.  In this case,
       use a lower number.

TxIntDelay
----------

:Valid Range:   0-65535 (0=off)
:Default Value: 8

This value delays the generation of transmit interrupts in units of
1.024 microseconds.  Transmit interrupt reduction can improve CPU
efficiency if properly tuned for specific network traffic.  If the
system is reporting dropped transmits, this value may be set too high
causing the driver to run out of available transmit descriptors.

TxAbsIntDelay
-------------

(This parameter is supported only on 82540, 82545 and later adapters.)

:Valid Range:   0-65535 (0=off)
:Default Value: 32

This value, in units of 1.024 microseconds, limits the delay in which a
transmit interrupt is generated.  Useful only if TxIntDelay is non-zero,
this value ensures that an interrupt is generated after the initial
packet is sent on the wire within the set amount of time.  Proper tuning,
along with TxIntDelay, may improve traffic throughput in specific
network conditions.

XsumRX
------

(This parameter is NOT supported on the 82542-based adapter.)

:Valid Range:   0-1
:Default Value: 1

A value of '1' indicates that the driver should enable IP checksum
offload for received packets (both UDP and TCP) to the adapter hardware.

Copybreak
---------

:Valid Range:   0-xxxxxxx (0=off)
:Default Value: 256
:Usage: modprobe e1000.ko copybreak=128

Driver copies all packets below or equaling this size to a fresh RX
buffer before handing it up the stack.

This parameter is different than other parameters, in that it is a
single (not 1,1,1 etc.) parameter applied to all driver instances and
it is also available during runtime at
/sys/module/e1000/parameters/copybreak

SmartPowerDownEnable
--------------------

:Valid Range: 0-1
:Default Value:  0 (disabled)

Allows PHY to turn off in lower power states. The user can turn off
this parameter in supported chipsets.

Speed and Duplex Configuration
==============================

Three keywords are used to control the speed and duplex configuration.
These keywords are Speed, Duplex, and AutoNeg.

If the board uses a fiber interface, these keywords are ignored, and the
fiber interface board only links at 1000 Mbps full-duplex.

For copper-based boards, the keywords interact as follows:

- The default operation is auto-negotiate.  The board advertises all
  supported speed and duplex combinations, and it links at the highest
  common speed and duplex mode IF the link partner is set to auto-negotiate.

- If Speed = 1000, limited auto-negotiation is enabled and only 1000 Mbps
  is advertised (The 1000BaseT spec requires auto-negotiation.)

- If Speed = 10 or 100, then both Speed and Duplex should be set.  Auto-
  negotiation is disabled, and the AutoNeg parameter is ignored.  Partner
  SHOULD also be forced.

The AutoNeg parameter is used when more control is required over the
auto-negotiation process.  It should be used when you wish to control which
speed and duplex combinations are advertised during the auto-negotiation
process.

The parameter may be specified as either a decimal or hexadecimal value as
determined by the bitmap below.

============== ====== ====== ======= ======= ====== ====== ======= ======
Bit position   7      6      5       4       3      2      1       0
Decimal Value  128    64     32      16      8      4      2       1
Hex value      80     40     20      10      8      4      2       1
Speed (Mbps)   N/A    N/A    1000    N/A     100    100    10      10
Duplex                       Full            Full   Half   Full    Half
============== ====== ====== ======= ======= ====== ====== ======= ======

Some examples of using AutoNeg::

  modprobe e1000 AutoNeg=0x01 (Restricts autonegotiation to 10 Half)
  modprobe e1000 AutoNeg=1 (Same as above)
  modprobe e1000 AutoNeg=0x02 (Restricts autonegotiation to 10 Full)
  modprobe e1000 AutoNeg=0x03 (Restricts autonegotiation to 10 Half or 10 Full)
  modprobe e1000 AutoNeg=0x04 (Restricts autonegotiation to 100 Half)
  modprobe e1000 AutoNeg=0x05 (Restricts autonegotiation to 10 Half or 100
  Half)
  modprobe e1000 AutoNeg=0x020 (Restricts autonegotiation to 1000 Full)
  modprobe e1000 AutoNeg=32 (Same as above)

Note that when this parameter is used, Speed and Duplex must not be specified.

If the link partner is forced to a specific speed and duplex, then this
parameter should not be used.  Instead, use the Speed and Duplex parameters
previously mentioned to force the adapter to the same speed and duplex.

Additional Configurations
=========================

Jumbo Frames
------------

  Jumbo Frames support is enabled by changing the MTU to a value larger than
  the default of 1500.  Use the ifconfig command to increase the MTU size.
  For example::

       ifconfig eth<x> mtu 9000 up

  This setting is not saved across reboots.  It can be made permanent if
  you add::

       MTU=9000

  to the file /etc/sysconfig/network-scripts/ifcfg-eth<x>.  This example
  applies to the Red Hat distributions; other distributions may store this
  setting in a different location.

Notes:
  Degradation in throughput performance may be observed in some Jumbo frames
  environments. If this is observed, increasing the application's socket buffer
  size and/or increasing the /proc/sys/net/ipv4/tcp_*mem entry values may help.
  See the specific application manual and /usr/src/linux*/Documentation/
  networking/ip-sysctl.txt for more details.

  - The maximum MTU setting for Jumbo Frames is 16110.  This value coincides
    with the maximum Jumbo Frames size of 16128.

  - Using Jumbo frames at 10 or 100 Mbps is not supported and may result in
    poor performance or loss of link.

  - Adapters based on the Intel(R) 82542 and 82573V/E controller do not
    support Jumbo Frames. These correspond to the following product names::

     Intel(R) PRO/1000 Gigabit Server Adapter
     Intel(R) PRO/1000 PM Network Connection

ethtool
-------

  The driver utilizes the ethtool interface for driver configuration and
  diagnostics, as well as displaying statistical information.  The ethtool
  version 1.6 or later is required for this functionality.

  The latest release of ethtool can be found from
  https://www.kernel.org/pub/software/network/ethtool/

Enabling Wake on LAN* (WoL)
---------------------------

  WoL is configured through the ethtool* utility.

  WoL will be enabled on the system during the next shut down or reboot.
  For this driver version, in order to enable WoL, the e1000 driver must be
  loaded when shutting down or rebooting the system.

Support
=======

For general information, go to the Intel support website at:

    http://support.intel.com

or the Intel Wired Networking project hosted by Sourceforge at:

    http://sourceforge.net/projects/e1000

If an issue is identified with the released source code on the supported
kernel with a supported adapter, email the specific information related
to the issue to e1000-devel@lists.sf.net