High CPU usage of multipathd with low polling_interval

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