linux-next/Documentation/networking/e1000e.txt

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

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

Contents
========

- Identifying Your Adapter
- Command Line Parameters
- Additional Configurations
- Support

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

The e1000e driver supports all PCI Express Intel(R) Gigabit Network
Connections, except those that are 82575, 82576 and 82580-based*.

* NOTE: The Intel(R) PRO/1000 P Dual Port Server Adapter is supported by
  the e1000 driver, not the e1000e driver due to the 82546 part being used
  behind a PCI Express bridge.

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

InterruptThrottleRate
---------------------
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.

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.

NOTE:  When e1000e 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 e1000e 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.

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

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.

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
-------------
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.

Copybreak
---------
Valid Range:   0-xxxxxxx (0=off)
Default Value: 256

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/e1000e/parameters/copybreak

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

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

KumeranLockLoss
---------------
Valid Range: 0-1
Default Value: 1 (enabled)

This workaround skips resetting the PHY at shutdown for the initial
silicon releases of ICH8 systems.

IntMode
-------
Valid Range: 0-2 (0=legacy, 1=MSI, 2=MSI-X)
Default Value: 2

Allows changing the interrupt mode at module load time, without requiring a
recompile. If the driver load fails to enable a specific interrupt mode, the
driver will try other interrupt modes, from least to most compatible.  The
interrupt order is MSI-X, MSI, Legacy.  If specifying MSI (IntMode=1)
interrupts, only MSI and Legacy will be attempted.

CrcStripping
------------
Valid Range: 0-1
Default Value: 1 (enabled)

Strip the CRC from received packets before sending up the network stack.  If
you have a machine with a BMC enabled but cannot receive IPMI traffic after
loading or enabling the driver, try disabling this feature.

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

If set to 1, configure the hardware to ignore all write/erase cycles to the
GbE region in the ICHx NVM (in order to prevent accidental corruption of the
NVM). This feature can be disabled by setting the parameter to 0 during initial
driver load.
NOTE: The machine must be power cycled (full off/on) when enabling NVM writes
via setting the parameter to zero. Once the NVM has been locked (via the
parameter at 1 when the driver loads) it cannot be unlocked except via power
cycle.

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.

  Notes:

  - The maximum MTU setting for Jumbo Frames is 9216.  This value coincides
    with the maximum Jumbo Frames size of 9234 bytes.

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

  - Some adapters limit Jumbo Frames sized packets to a maximum of
    4096 bytes and some adapters do not support Jumbo Frames.

  - Jumbo Frames cannot be configured on an 82579-based Network device, if
    MACSec is enabled on the system.

  ethtool
  -------
  The driver utilizes the ethtool interface for driver configuration and
  diagnostics, as well as displaying statistical information.  We
  strongly recommend downloading the latest version of ethtool at:

  http://ftp.kernel.org/pub/software/network/ethtool/

  NOTE: When validating enable/disable tests on some parts (82578, for example)
  you need to add a few seconds between tests when working with ethtool.

  Speed and Duplex
  ----------------
  Speed and Duplex are configured through the ethtool* utility. For
  instructions,  refer to the ethtool man page.

  Enabling Wake on LAN* (WoL)
  ---------------------------
  WoL is configured through the ethtool* utility. For instructions on
  enabling WoL with ethtool, refer to the ethtool man page.

  WoL will be enabled on the system during the next shut down or reboot.
  For this driver version, in order to enable WoL, the e1000e driver must be
  loaded when shutting down or rebooting the system.

  In most cases Wake On LAN is only supported on port A for multiple port
  adapters. To verify if a port supports Wake on Lan run ethtool eth<X>.

Support
=======

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

    www.intel.com/support/

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