Intel Flow Director results in TCP Out of Order traffic

Solution Verified - Updated -

Issue

  • Intel Flow Director results in TCP Out of Order traffic
  • TCP throughput and performance can be seriously degraded as a side effect.
  • FDir ATR (Application Targeted Receive) functionality of ixgbe results in TCP OoO or OfO TCPOFOQueue counters growing in netstat -s
  • How to avoid negative performance impact in multiprocessing environments on process migration demonstrated by research paper "Why 
Does 
Flow 
Director
 Cause 
Packet 
Reordering?
" by Wenji
 Wu, 
Phil 
De Mar, 
Matt 
Crawford of Fermilab - http://arxiv.org/pdf/1106.0443.pdf

Environment

  • Red Hat Enterprise Linux
  • Intel 82598, 82599, X520, X540, X550 or other network interface card using ixgbe driver
  • Intel Flow Director in ATR (Application Targeted Receive) mode
  • TCP traffic
  • TCPOFOQueue statistic in /proc/net/netstat shows large number
  • Unpinned processes migrating between CPU cores due to regular CPU scheduling

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