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Diffstat (limited to 'Documentation/infiniband/ipoib.txt')
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diff --git a/Documentation/infiniband/ipoib.txt b/Documentation/infiniband/ipoib.txt deleted file mode 100644 index 47c1dd9818f2..000000000000 --- a/Documentation/infiniband/ipoib.txt +++ /dev/null @@ -1,105 +0,0 @@ -IP OVER INFINIBAND - - The ib_ipoib driver is an implementation of the IP over InfiniBand - protocol as specified by RFC 4391 and 4392, issued by the IETF ipoib - working group. It is a "native" implementation in the sense of - setting the interface type to ARPHRD_INFINIBAND and the hardware - address length to 20 (earlier proprietary implementations - masqueraded to the kernel as ethernet interfaces). - -Partitions and P_Keys - - When the IPoIB driver is loaded, it creates one interface for each - port using the P_Key at index 0. To create an interface with a - different P_Key, write the desired P_Key into the main interface's - /sys/class/net/<intf name>/create_child file. For example: - - echo 0x8001 > /sys/class/net/ib0/create_child - - This will create an interface named ib0.8001 with P_Key 0x8001. To - remove a subinterface, use the "delete_child" file: - - echo 0x8001 > /sys/class/net/ib0/delete_child - - The P_Key for any interface is given by the "pkey" file, and the - main interface for a subinterface is in "parent." - - Child interface create/delete can also be done using IPoIB's - rtnl_link_ops, where children created using either way behave the same. - -Datagram vs Connected modes - - The IPoIB driver supports two modes of operation: datagram and - connected. The mode is set and read through an interface's - /sys/class/net/<intf name>/mode file. - - In datagram mode, the IB UD (Unreliable Datagram) transport is used - and so the interface MTU has is equal to the IB L2 MTU minus the - IPoIB encapsulation header (4 bytes). For example, in a typical IB - fabric with a 2K MTU, the IPoIB MTU will be 2048 - 4 = 2044 bytes. - - In connected mode, the IB RC (Reliable Connected) transport is used. - Connected mode takes advantage of the connected nature of the IB - transport and allows an MTU up to the maximal IP packet size of 64K, - which reduces the number of IP packets needed for handling large UDP - datagrams, TCP segments, etc and increases the performance for large - messages. - - In connected mode, the interface's UD QP is still used for multicast - and communication with peers that don't support connected mode. In - this case, RX emulation of ICMP PMTU packets is used to cause the - networking stack to use the smaller UD MTU for these neighbours. - -Stateless offloads - - If the IB HW supports IPoIB stateless offloads, IPoIB advertises - TCP/IP checksum and/or Large Send (LSO) offloading capability to the - network stack. - - Large Receive (LRO) offloading is also implemented and may be turned - on/off using ethtool calls. Currently LRO is supported only for - checksum offload capable devices. - - Stateless offloads are supported only in datagram mode. - -Interrupt moderation - - If the underlying IB device supports CQ event moderation, one can - use ethtool to set interrupt mitigation parameters and thus reduce - the overhead incurred by handling interrupts. The main code path of - IPoIB doesn't use events for TX completion signaling so only RX - moderation is supported. - -Debugging Information - - By compiling the IPoIB driver with CONFIG_INFINIBAND_IPOIB_DEBUG set - to 'y', tracing messages are compiled into the driver. They are - turned on by setting the module parameters debug_level and - mcast_debug_level to 1. These parameters can be controlled at - runtime through files in /sys/module/ib_ipoib/. - - CONFIG_INFINIBAND_IPOIB_DEBUG also enables files in the debugfs - virtual filesystem. By mounting this filesystem, for example with - - mount -t debugfs none /sys/kernel/debug - - it is possible to get statistics about multicast groups from the - files /sys/kernel/debug/ipoib/ib0_mcg and so on. - - The performance impact of this option is negligible, so it - is safe to enable this option with debug_level set to 0 for normal - operation. - - CONFIG_INFINIBAND_IPOIB_DEBUG_DATA enables even more debug output in - the data path when data_debug_level is set to 1. However, even with - the output disabled, enabling this configuration option will affect - performance, because it adds tests to the fast path. - -References - - Transmission of IP over InfiniBand (IPoIB) (RFC 4391) - http://ietf.org/rfc/rfc4391.txt - IP over InfiniBand (IPoIB) Architecture (RFC 4392) - http://ietf.org/rfc/rfc4392.txt - IP over InfiniBand: Connected Mode (RFC 4755) - http://ietf.org/rfc/rfc4755.txt |