Commit da8c01c4 authored by Jeff Kirsher's avatar Jeff Kirsher Committed by David S. Miller
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e1000e.txt: Add e1000e documentation 



Adds documentation for the e1000e networking driver.

Signed-off-by: default avatarJeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 2bff89c3

Documentation/networking/e1000e.txt

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Linux* Driver for Intel(R) Network Connection

===============================================================



Intel Gigabit Linux driver.

Copyright(c) 1999 - 2010 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 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 (enabled)



Set the hardware to ignore all write/erase cycles to the GbE region in the

ICHx NVM (non-volatile memory).  This feature can be disabled by the

WriteProtectNVM module parameter (enabled by default) only after a hardware

reset, but the machine must be power cycled before trying to enable writes.



Note: the kernel boot option iomem=relaxed may need to be set if the kernel

config option CONFIG_STRICT_DEVMEM=y, if the root user wants to write the

NVM from user space via ethtool.



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.





  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://sourceforge.net/projects/gkernel.



  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