394 lines
13 KiB
ReStructuredText
394 lines
13 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0
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.. include:: <isonum.txt>
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=============================================
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Chelsio N210 10Gb Ethernet Network Controller
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=============================================
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Driver Release Notes for Linux
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Version 2.1.1
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June 20, 2005
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.. Contents
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INTRODUCTION
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FEATURES
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PERFORMANCE
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DRIVER MESSAGES
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KNOWN ISSUES
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SUPPORT
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Introduction
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============
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This document describes the Linux driver for Chelsio 10Gb Ethernet Network
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Controller. This driver supports the Chelsio N210 NIC and is backward
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compatible with the Chelsio N110 model 10Gb NICs.
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Features
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========
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Adaptive Interrupts (adaptive-rx)
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---------------------------------
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This feature provides an adaptive algorithm that adjusts the interrupt
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coalescing parameters, allowing the driver to dynamically adapt the latency
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settings to achieve the highest performance during various types of network
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load.
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The interface used to control this feature is ethtool. Please see the
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ethtool manpage for additional usage information.
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By default, adaptive-rx is disabled.
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To enable adaptive-rx::
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ethtool -C <interface> adaptive-rx on
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To disable adaptive-rx, use ethtool::
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ethtool -C <interface> adaptive-rx off
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After disabling adaptive-rx, the timer latency value will be set to 50us.
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You may set the timer latency after disabling adaptive-rx::
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ethtool -C <interface> rx-usecs <microseconds>
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An example to set the timer latency value to 100us on eth0::
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ethtool -C eth0 rx-usecs 100
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You may also provide a timer latency value while disabling adaptive-rx::
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ethtool -C <interface> adaptive-rx off rx-usecs <microseconds>
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If adaptive-rx is disabled and a timer latency value is specified, the timer
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will be set to the specified value until changed by the user or until
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adaptive-rx is enabled.
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To view the status of the adaptive-rx and timer latency values::
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ethtool -c <interface>
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TCP Segmentation Offloading (TSO) Support
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-----------------------------------------
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This feature, also known as "large send", enables a system's protocol stack
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to offload portions of outbound TCP processing to a network interface card
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thereby reducing system CPU utilization and enhancing performance.
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The interface used to control this feature is ethtool version 1.8 or higher.
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Please see the ethtool manpage for additional usage information.
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By default, TSO is enabled.
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To disable TSO::
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ethtool -K <interface> tso off
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To enable TSO::
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ethtool -K <interface> tso on
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To view the status of TSO::
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ethtool -k <interface>
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Performance
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===========
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The following information is provided as an example of how to change system
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parameters for "performance tuning" an what value to use. You may or may not
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want to change these system parameters, depending on your server/workstation
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application. Doing so is not warranted in any way by Chelsio Communications,
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and is done at "YOUR OWN RISK". Chelsio will not be held responsible for loss
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of data or damage to equipment.
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Your distribution may have a different way of doing things, or you may prefer
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a different method. These commands are shown only to provide an example of
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what to do and are by no means definitive.
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Making any of the following system changes will only last until you reboot
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your system. You may want to write a script that runs at boot-up which
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includes the optimal settings for your system.
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Setting PCI Latency Timer::
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setpci -d 1425::
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* 0x0c.l=0x0000F800
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Disabling TCP timestamp::
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sysctl -w net.ipv4.tcp_timestamps=0
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Disabling SACK::
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sysctl -w net.ipv4.tcp_sack=0
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Setting large number of incoming connection requests::
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sysctl -w net.ipv4.tcp_max_syn_backlog=3000
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Setting maximum receive socket buffer size::
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sysctl -w net.core.rmem_max=1024000
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Setting maximum send socket buffer size::
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sysctl -w net.core.wmem_max=1024000
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Set smp_affinity (on a multiprocessor system) to a single CPU::
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echo 1 > /proc/irq/<interrupt_number>/smp_affinity
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Setting default receive socket buffer size::
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sysctl -w net.core.rmem_default=524287
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Setting default send socket buffer size::
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sysctl -w net.core.wmem_default=524287
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Setting maximum option memory buffers::
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sysctl -w net.core.optmem_max=524287
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Setting maximum backlog (# of unprocessed packets before kernel drops)::
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sysctl -w net.core.netdev_max_backlog=300000
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Setting TCP read buffers (min/default/max)::
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sysctl -w net.ipv4.tcp_rmem="10000000 10000000 10000000"
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Setting TCP write buffers (min/pressure/max)::
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sysctl -w net.ipv4.tcp_wmem="10000000 10000000 10000000"
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Setting TCP buffer space (min/pressure/max)::
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sysctl -w net.ipv4.tcp_mem="10000000 10000000 10000000"
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TCP window size for single connections:
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The receive buffer (RX_WINDOW) size must be at least as large as the
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Bandwidth-Delay Product of the communication link between the sender and
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receiver. Due to the variations of RTT, you may want to increase the buffer
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size up to 2 times the Bandwidth-Delay Product. Reference page 289 of
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"TCP/IP Illustrated, Volume 1, The Protocols" by W. Richard Stevens.
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At 10Gb speeds, use the following formula::
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RX_WINDOW >= 1.25MBytes * RTT(in milliseconds)
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Example for RTT with 100us: RX_WINDOW = (1,250,000 * 0.1) = 125,000
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RX_WINDOW sizes of 256KB - 512KB should be sufficient.
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Setting the min, max, and default receive buffer (RX_WINDOW) size::
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sysctl -w net.ipv4.tcp_rmem="<min> <default> <max>"
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TCP window size for multiple connections:
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The receive buffer (RX_WINDOW) size may be calculated the same as single
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connections, but should be divided by the number of connections. The
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smaller window prevents congestion and facilitates better pacing,
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especially if/when MAC level flow control does not work well or when it is
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not supported on the machine. Experimentation may be necessary to attain
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the correct value. This method is provided as a starting point for the
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correct receive buffer size.
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Setting the min, max, and default receive buffer (RX_WINDOW) size is
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performed in the same manner as single connection.
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Driver Messages
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===============
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The following messages are the most common messages logged by syslog. These
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may be found in /var/log/messages.
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Driver up::
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Chelsio Network Driver - version 2.1.1
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NIC detected::
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eth#: Chelsio N210 1x10GBaseX NIC (rev #), PCIX 133MHz/64-bit
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Link up::
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eth#: link is up at 10 Gbps, full duplex
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Link down::
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eth#: link is down
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Known Issues
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============
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These issues have been identified during testing. The following information
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is provided as a workaround to the problem. In some cases, this problem is
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inherent to Linux or to a particular Linux Distribution and/or hardware
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platform.
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1. Large number of TCP retransmits on a multiprocessor (SMP) system.
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On a system with multiple CPUs, the interrupt (IRQ) for the network
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controller may be bound to more than one CPU. This will cause TCP
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retransmits if the packet data were to be split across different CPUs
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and re-assembled in a different order than expected.
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To eliminate the TCP retransmits, set smp_affinity on the particular
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interrupt to a single CPU. You can locate the interrupt (IRQ) used on
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the N110/N210 by using ifconfig::
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ifconfig <dev_name> | grep Interrupt
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Set the smp_affinity to a single CPU::
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echo 1 > /proc/irq/<interrupt_number>/smp_affinity
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It is highly suggested that you do not run the irqbalance daemon on your
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system, as this will change any smp_affinity setting you have applied.
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The irqbalance daemon runs on a 10 second interval and binds interrupts
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to the least loaded CPU determined by the daemon. To disable this daemon::
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chkconfig --level 2345 irqbalance off
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By default, some Linux distributions enable the kernel feature,
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irqbalance, which performs the same function as the daemon. To disable
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this feature, add the following line to your bootloader::
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noirqbalance
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Example using the Grub bootloader::
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title Red Hat Enterprise Linux AS (2.4.21-27.ELsmp)
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root (hd0,0)
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kernel /vmlinuz-2.4.21-27.ELsmp ro root=/dev/hda3 noirqbalance
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initrd /initrd-2.4.21-27.ELsmp.img
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2. After running insmod, the driver is loaded and the incorrect network
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interface is brought up without running ifup.
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When using 2.4.x kernels, including RHEL kernels, the Linux kernel
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invokes a script named "hotplug". This script is primarily used to
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automatically bring up USB devices when they are plugged in, however,
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the script also attempts to automatically bring up a network interface
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after loading the kernel module. The hotplug script does this by scanning
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the ifcfg-eth# config files in /etc/sysconfig/network-scripts, looking
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for HWADDR=<mac_address>.
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If the hotplug script does not find the HWADDRR within any of the
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ifcfg-eth# files, it will bring up the device with the next available
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interface name. If this interface is already configured for a different
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network card, your new interface will have incorrect IP address and
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network settings.
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To solve this issue, you can add the HWADDR=<mac_address> key to the
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interface config file of your network controller.
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To disable this "hotplug" feature, you may add the driver (module name)
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to the "blacklist" file located in /etc/hotplug. It has been noted that
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this does not work for network devices because the net.agent script
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does not use the blacklist file. Simply remove, or rename, the net.agent
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script located in /etc/hotplug to disable this feature.
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3. Transport Protocol (TP) hangs when running heavy multi-connection traffic
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on an AMD Opteron system with HyperTransport PCI-X Tunnel chipset.
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If your AMD Opteron system uses the AMD-8131 HyperTransport PCI-X Tunnel
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chipset, you may experience the "133-Mhz Mode Split Completion Data
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Corruption" bug identified by AMD while using a 133Mhz PCI-X card on the
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bus PCI-X bus.
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AMD states, "Under highly specific conditions, the AMD-8131 PCI-X Tunnel
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can provide stale data via split completion cycles to a PCI-X card that
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is operating at 133 Mhz", causing data corruption.
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AMD's provides three workarounds for this problem, however, Chelsio
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recommends the first option for best performance with this bug:
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For 133Mhz secondary bus operation, limit the transaction length and
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the number of outstanding transactions, via BIOS configuration
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programming of the PCI-X card, to the following:
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Data Length (bytes): 1k
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Total allowed outstanding transactions: 2
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Please refer to AMD 8131-HT/PCI-X Errata 26310 Rev 3.08 August 2004,
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section 56, "133-MHz Mode Split Completion Data Corruption" for more
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details with this bug and workarounds suggested by AMD.
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It may be possible to work outside AMD's recommended PCI-X settings, try
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increasing the Data Length to 2k bytes for increased performance. If you
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have issues with these settings, please revert to the "safe" settings
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and duplicate the problem before submitting a bug or asking for support.
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.. note::
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The default setting on most systems is 8 outstanding transactions
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and 2k bytes data length.
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4. On multiprocessor systems, it has been noted that an application which
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is handling 10Gb networking can switch between CPUs causing degraded
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and/or unstable performance.
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If running on an SMP system and taking performance measurements, it
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is suggested you either run the latest netperf-2.4.0+ or use a binding
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tool such as Tim Hockin's procstate utilities (runon)
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<http://www.hockin.org/~thockin/procstate/>.
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Binding netserver and netperf (or other applications) to particular
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CPUs will have a significant difference in performance measurements.
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You may need to experiment which CPU to bind the application to in
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order to achieve the best performance for your system.
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If you are developing an application designed for 10Gb networking,
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please keep in mind you may want to look at kernel functions
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sched_setaffinity & sched_getaffinity to bind your application.
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If you are just running user-space applications such as ftp, telnet,
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etc., you may want to try the runon tool provided by Tim Hockin's
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procstate utility. You could also try binding the interface to a
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particular CPU: runon 0 ifup eth0
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Support
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=======
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If you have problems with the software or hardware, please contact our
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customer support team via email at support@chelsio.com or check our website
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at http://www.chelsio.com
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-------------------------------------------------------------------------------
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::
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Chelsio Communications
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370 San Aleso Ave.
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Suite 100
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Sunnyvale, CA 94085
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http://www.chelsio.com
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License, version 2, as
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published by the Free Software Foundation.
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You should have received a copy of the GNU General Public License along
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with this program; if not, write to the Free Software Foundation, Inc.,
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59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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THIS SOFTWARE IS PROVIDED ``AS IS`` AND WITHOUT ANY EXPRESS OR IMPLIED
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WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
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MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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Copyright |copy| 2003-2005 Chelsio Communications. All rights reserved.
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