NetworkManager consumes 100% CPU with large regularly-updated routing tables

Solution Verified - Updated -

Issue

  • NetworkManager consumes 100% CPU with large regularly-updated routing tables
  • We have two routing tables, each table has approximately 1 million IPv4 routes and 200,000 IPv6 routes. Total routes ~2.4M. We also run a custom routing protocol which regularly updates these tables at a rate of 15 changes per second (~900 changes per minute). Just having the routes present is not a problem, but when routes are updated then NetworkManager CPU usage spikes to 100% and stays there. Any nmcli command takes a long time to return.

Environment

  • Red Hat Enterprise Linux 9.3 and earlier
  • NetworkManager-1.44.0 and earlier
  • Large routing tables with rapid routing table updates

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