High CPU usage of multipathd with low polling_interval

Solution Verified - Updated -

Issue

  • We are using multipathd for a very large number of devices (1572 native devices),
  • Due to grid software heartbeat constraints, we are required to aggressively monitor down paths to failover quickly.
  • We set polling_interval 1 in multipath.conf (which effectively means checking each path every 4 seconds).
  • Storage array is EMC VMAX with path_checker tur.
  • We see multipathd using a very high amount of CPU for this amount of work:
  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND                                        
16421 root      RT   0 16.0g  64m 3372 S 36.8  0.1 686:38.94 multipathd

Environment

  • Red Hat Enterprise Linux 6.5
  • device-mapper-multipath-0.4.9-72.el6
  • polling_interval 1 set in /etc/multipath.conf

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