Large receive offload

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In computer networking, large receive offload (LRO) is a technique for increasing inbound throughput of high-bandwidth network connections by reducing CPU overhead. It works by aggregating multiple incoming packets from a single stream into a larger buffer before they are passed higher up the networking stack, thus reducing the number of packets that have to be processed. In Linux, it is generally used in conjunction with the New API (NAPI) to also reduce the number of interrupts.

According to benchmarks, even implementing this technique entirely in software can increase network performance significantly.[1][2][3] As of April 2007, the Linux kernel supports LRO for TCP in software only. FreeBSD 8 supports LRO in hardware on adapters that support it.[4][5][6] [7]

LRO should not be used on machines acting as routers, as it breaks the end-to-end principle and can significantly impact performance.[8][9]

See also

References

  1. ↑ Jonathan Corbet (2007-08-01). "Large receive offload". LWN.net. Retrieved 2007-08-22. 
  2. ↑ Aravind Menon, Willy Zwaenepoel (2008-04-28). Optimizing TCP Receive Performance. 
  3. ↑ Andrew Gallatin (2007-07-25). "lro: Generic Large Receive Offload for TCP traffic". linux-kernel mailing list. http://lkml.org/lkml/2007/7/25/313. Retrieved 2007-08-22.
  4. ↑ http://www.freebsd.org/cgi/man.cgi?cxgb
  5. ↑ http://www.freebsd.org/cgi/man.cgi?mxge
  6. ↑ http://www.freebsd.org/cgi/man.cgi?nxge
  7. ↑ "Poor TCP performance can occur in Linux virtual machines with LRO enabled". kb.vmware.com. 2011-07-04. Retrieved 2011-08-17. 
  8. ↑ "Linux* Base Driver for the Intel(R) Ethernet 10 Gigabit PCI Express Family of Adapters". Intel Corporation. 2013-02-12. Retrieved 2013-04-24. 
  9. ↑ "Disable LRO for all NICs that have LRO enabled". Red Hat, Inc. 2013-01-10. Retrieved 2013-04-24. 
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