RHEL7: Very high %sys CPU usage in __neigh_create()

Solution In Progress - Updated -

Issue

  • We are in the process of migrating our environment from RHEL 6.7 to RHEL 7.5 and we are seeing quite a big difference in %sys kernel CPU usage between these two major versions. The same software is producing less kernel CPU load in RHEL 6.7 than it does in 7.5.
  • UDP sendto() occasionally returns -EINVAL. See also: https://access.redhat.com/solutions/2985371, although in this case much larger gc_thresh values are required.

Environment

  • Red Hat Enterprise Linux
    • kernel 3.10.0-862.14.4.el7.x86_64
  • 3rd party GTP tunnels
  • UDP application that sendto() 1000s of different IP Addresses

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