839fcaba35
The following patch adds experimental support for IPoIB connected mode, as defined by the draft from the IETF ipoib working group. The idea is to increase performance by increasing the MTU from the maximum of 2K (theoretically 4K) supported by IPoIB on top of UD. With this code, I'm able to get 800MByte/sec or more with netperf without options on a Mellanox 4x back-to-back DDR system. Some notes on code: 1. SRQ is used for scalability to large cluster sizes 2. Only RC connections are used (UC does not support SRQ now) 3. Retry count is set to 0 since spec draft warns against retries 4. Each connection is used for data transfers in only 1 direction, so each connection is either active(TX) or passive (RX). 2 sides that want to communicate create 2 connections. 5. Each active (TX) connection has a separate CQ for send completions - this keeps the code simple without CQ resize and other tricks 6. To detect stale passive side connections (where the remote side is down), we keep an LRU list of passive connections (updated once per second per connection) and destroy a connection after it has been unused for several seconds. The LRU rule makes it possible to avoid scanning connections that have recently been active. Signed-off-by: Michael S. Tsirkin <mst@mellanox.co.il> Signed-off-by: Roland Dreier <rolandd@cisco.com> |
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