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diff --git a/Documentation/networking/cxgb.txt b/Documentation/networking/cxgb.txt new file mode 100644 index 00000000000..76324638626 --- /dev/null +++ b/Documentation/networking/cxgb.txt @@ -0,0 +1,352 @@ + Chelsio N210 10Gb Ethernet Network Controller + + Driver Release Notes for Linux + + Version 2.1.1 + + June 20, 2005 + +CONTENTS +======== + INTRODUCTION + FEATURES + PERFORMANCE + DRIVER MESSAGES + KNOWN ISSUES + SUPPORT + + +INTRODUCTION +============ + + This document describes the Linux driver for Chelsio 10Gb Ethernet Network + Controller. This driver supports the Chelsio N210 NIC and is backward + compatible with the Chelsio N110 model 10Gb NICs. + + +FEATURES +======== + + Adaptive Interrupts (adaptive-rx) + --------------------------------- + + This feature provides an adaptive algorithm that adjusts the interrupt + coalescing parameters, allowing the driver to dynamically adapt the latency + settings to achieve the highest performance during various types of network + load. + + The interface used to control this feature is ethtool. Please see the + ethtool manpage for additional usage information. + + By default, adaptive-rx is disabled. + To enable adaptive-rx: + + ethtool -C <interface> adaptive-rx on + + To disable adaptive-rx, use ethtool: + + ethtool -C <interface> adaptive-rx off + + After disabling adaptive-rx, the timer latency value will be set to 50us. + You may set the timer latency after disabling adaptive-rx: + + ethtool -C <interface> rx-usecs <microseconds> + + An example to set the timer latency value to 100us on eth0: + + ethtool -C eth0 rx-usecs 100 + + You may also provide a timer latency value while disabling adpative-rx: + + ethtool -C <interface> adaptive-rx off rx-usecs <microseconds> + + If adaptive-rx is disabled and a timer latency value is specified, the timer + will be set to the specified value until changed by the user or until + adaptive-rx is enabled. + + To view the status of the adaptive-rx and timer latency values: + + ethtool -c <interface> + + + TCP Segmentation Offloading (TSO) Support + ----------------------------------------- + + This feature, also known as "large send", enables a system's protocol stack + to offload portions of outbound TCP processing to a network interface card + thereby reducing system CPU utilization and enhancing performance. + + The interface used to control this feature is ethtool version 1.8 or higher. + Please see the ethtool manpage for additional usage information. + + By default, TSO is enabled. + To disable TSO: + + ethtool -K <interface> tso off + + To enable TSO: + + ethtool -K <interface> tso on + + To view the status of TSO: + + ethtool -k <interface> + + +PERFORMANCE +=========== + + The following information is provided as an example of how to change system + parameters for "performance tuning" an what value to use. You may or may not + want to change these system parameters, depending on your server/workstation + application. Doing so is not warranted in any way by Chelsio Communications, + and is done at "YOUR OWN RISK". Chelsio will not be held responsible for loss + of data or damage to equipment. + + Your distribution may have a different way of doing things, or you may prefer + a different method. These commands are shown only to provide an example of + what to do and are by no means definitive. + + Making any of the following system changes will only last until you reboot + your system. You may want to write a script that runs at boot-up which + includes the optimal settings for your system. + + Setting PCI Latency Timer: + setpci -d 1425:* 0x0c.l=0x0000F800 + + Disabling TCP timestamp: + sysctl -w net.ipv4.tcp_timestamps=0 + + Disabling SACK: + sysctl -w net.ipv4.tcp_sack=0 + + Setting large number of incoming connection requests: + sysctl -w net.ipv4.tcp_max_syn_backlog=3000 + + Setting maximum receive socket buffer size: + sysctl -w net.core.rmem_max=1024000 + + Setting maximum send socket buffer size: + sysctl -w net.core.wmem_max=1024000 + + Set smp_affinity (on a multiprocessor system) to a single CPU: + echo 1 > /proc/irq/<interrupt_number>/smp_affinity + + Setting default receive socket buffer size: + sysctl -w net.core.rmem_default=524287 + + Setting default send socket buffer size: + sysctl -w net.core.wmem_default=524287 + + Setting maximum option memory buffers: + sysctl -w net.core.optmem_max=524287 + + Setting maximum backlog (# of unprocessed packets before kernel drops): + sysctl -w net.core.netdev_max_backlog=300000 + + Setting TCP read buffers (min/default/max): + sysctl -w net.ipv4.tcp_rmem="10000000 10000000 10000000" + + Setting TCP write buffers (min/pressure/max): + sysctl -w net.ipv4.tcp_wmem="10000000 10000000 10000000" + + Setting TCP buffer space (min/pressure/max): + sysctl -w net.ipv4.tcp_mem="10000000 10000000 10000000" + + TCP window size for single connections: + The receive buffer (RX_WINDOW) size must be at least as large as the + Bandwidth-Delay Product of the communication link between the sender and + receiver. Due to the variations of RTT, you may want to increase the buffer + size up to 2 times the Bandwidth-Delay Product. Reference page 289 of + "TCP/IP Illustrated, Volume 1, The Protocols" by W. Richard Stevens. + At 10Gb speeds, use the following formula: + RX_WINDOW >= 1.25MBytes * RTT(in milliseconds) + Example for RTT with 100us: RX_WINDOW = (1,250,000 * 0.1) = 125,000 + RX_WINDOW sizes of 256KB - 512KB should be sufficient. + Setting the min, max, and default receive buffer (RX_WINDOW) size: + sysctl -w net.ipv4.tcp_rmem="<min> <default> <max>" + + TCP window size for multiple connections: + The receive buffer (RX_WINDOW) size may be calculated the same as single + connections, but should be divided by the number of connections. The + smaller window prevents congestion and facilitates better pacing, + especially if/when MAC level flow control does not work well or when it is + not supported on the machine. Experimentation may be necessary to attain + the correct value. This method is provided as a starting point fot the + correct receive buffer size. + Setting the min, max, and default receive buffer (RX_WINDOW) size is + performed in the same manner as single connection. + + +DRIVER MESSAGES +=============== + + The following messages are the most common messages logged by syslog. These + may be found in /var/log/messages. + + Driver up: + Chelsio Network Driver - version 2.1.1 + + NIC detected: + eth#: Chelsio N210 1x10GBaseX NIC (rev #), PCIX 133MHz/64-bit + + Link up: + eth#: link is up at 10 Gbps, full duplex + + Link down: + eth#: link is down + + +KNOWN ISSUES +============ + + These issues have been identified during testing. The following information + is provided as a workaround to the problem. In some cases, this problem is + inherent to Linux or to a particular Linux Distribution and/or hardware + platform. + + 1. Large number of TCP retransmits on a multiprocessor (SMP) system. + + On a system with multiple CPUs, the interrupt (IRQ) for the network + controller may be bound to more than one CPU. This will cause TCP + retransmits if the packet data were to be split across different CPUs + and re-assembled in a different order than expected. + + To eliminate the TCP retransmits, set smp_affinity on the particular + interrupt to a single CPU. You can locate the interrupt (IRQ) used on + the N110/N210 by using ifconfig: + ifconfig <dev_name> | grep Interrupt + Set the smp_affinity to a single CPU: + echo 1 > /proc/irq/<interrupt_number>/smp_affinity + + It is highly suggested that you do not run the irqbalance daemon on your + system, as this will change any smp_affinity setting you have applied. + The irqbalance daemon runs on a 10 second interval and binds interrupts + to the least loaded CPU determined by the daemon. To disable this daemon: + chkconfig --level 2345 irqbalance off + + By default, some Linux distributions enable the kernel feature, + irqbalance, which performs the same function as the daemon. To disable + this feature, add the following line to your bootloader: + noirqbalance + + Example using the Grub bootloader: + title Red Hat Enterprise Linux AS (2.4.21-27.ELsmp) + root (hd0,0) + kernel /vmlinuz-2.4.21-27.ELsmp ro root=/dev/hda3 noirqbalance + initrd /initrd-2.4.21-27.ELsmp.img + + 2. After running insmod, the driver is loaded and the incorrect network + interface is brought up without running ifup. + + When using 2.4.x kernels, including RHEL kernels, the Linux kernel + invokes a script named "hotplug". This script is primarily used to + automatically bring up USB devices when they are plugged in, however, + the script also attempts to automatically bring up a network interface + after loading the kernel module. The hotplug script does this by scanning + the ifcfg-eth# config files in /etc/sysconfig/network-scripts, looking + for HWADDR=<mac_address>. + + If the hotplug script does not find the HWADDRR within any of the + ifcfg-eth# files, it will bring up the device with the next available + interface name. If this interface is already configured for a different + network card, your new interface will have incorrect IP address and + network settings. + + To solve this issue, you can add the HWADDR=<mac_address> key to the + interface config file of your network controller. + + To disable this "hotplug" feature, you may add the driver (module name) + to the "blacklist" file located in /etc/hotplug. It has been noted that + this does not work for network devices because the net.agent script + does not use the blacklist file. Simply remove, or rename, the net.agent + script located in /etc/hotplug to disable this feature. + + 3. Transport Protocol (TP) hangs when running heavy multi-connection traffic + on an AMD Opteron system with HyperTransport PCI-X Tunnel chipset. + + If your AMD Opteron system uses the AMD-8131 HyperTransport PCI-X Tunnel + chipset, you may experience the "133-Mhz Mode Split Completion Data + Corruption" bug identified by AMD while using a 133Mhz PCI-X card on the + bus PCI-X bus. + + AMD states, "Under highly specific conditions, the AMD-8131 PCI-X Tunnel + can provide stale data via split completion cycles to a PCI-X card that + is operating at 133 Mhz", causing data corruption. + + AMD's provides three workarounds for this problem, however, Chelsio + recommends the first option for best performance with this bug: + + For 133Mhz secondary bus operation, limit the transaction length and + the number of outstanding transactions, via BIOS configuration + programming of the PCI-X card, to the following: + + Data Length (bytes): 1k + Total allowed outstanding transactions: 2 + + Please refer to AMD 8131-HT/PCI-X Errata 26310 Rev 3.08 August 2004, + section 56, "133-MHz Mode Split Completion Data Corruption" for more + details with this bug and workarounds suggested by AMD. + + It may be possible to work outside AMD's recommended PCI-X settings, try + increasing the Data Length to 2k bytes for increased performance. If you + have issues with these settings, please revert to the "safe" settings + and duplicate the problem before submitting a bug or asking for support. + + NOTE: The default setting on most systems is 8 outstanding transactions + and 2k bytes data length. + + 4. On multiprocessor systems, it has been noted that an application which + is handling 10Gb networking can switch between CPUs causing degraded + and/or unstable performance. + + If running on an SMP system and taking performance measurements, it + is suggested you either run the latest netperf-2.4.0+ or use a binding + tool such as Tim Hockin's procstate utilities (runon) + <http://www.hockin.org/~thockin/procstate/>. + + Binding netserver and netperf (or other applications) to particular + CPUs will have a significant difference in performance measurements. + You may need to experiment which CPU to bind the application to in + order to achieve the best performance for your system. + + If you are developing an application designed for 10Gb networking, + please keep in mind you may want to look at kernel functions + sched_setaffinity & sched_getaffinity to bind your application. + + If you are just running user-space applications such as ftp, telnet, + etc., you may want to try the runon tool provided by Tim Hockin's + procstate utility. You could also try binding the interface to a + particular CPU: runon 0 ifup eth0 + + +SUPPORT +======= + + If you have problems with the software or hardware, please contact our + customer support team via email at support@chelsio.com or check our website + at http://www.chelsio.com + +=============================================================================== + + Chelsio Communications + 370 San Aleso Ave. + Suite 100 + Sunnyvale, CA 94085 + http://www.chelsio.com + +This program is free software; you can redistribute it and/or modify +it under the terms of the GNU General Public License, version 2, as +published by the Free Software Foundation. + +You should have received a copy of the GNU General Public License along +with this program; if not, write to the Free Software Foundation, Inc., +59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. + +THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED +WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF +MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. + + Copyright (c) 2003-2005 Chelsio Communications. All rights reserved. + +=============================================================================== |