Peculiar Linux kernel performance problem on NUMA systems 

Problems due to zone_reclaim_mode.

Problems due to zone_reclaim_mode.

The Linux kernel can be inconsistent in enabling/disabling zone_reclaim_mode. This can result in odd performance problems:
  • Random huge CPU spikes resulting in large increases in latency and throughput.
  • Programs hanging indefinitely apparently doing nothing.
  • Symptoms appearing and disappearing suddenly.
  • After a reboot, the symptoms generally do not show again for some time.
To ensure that zone_reclaim_mode is disabled:
$ echo 0 > /proc/sys/vm/zone_reclaim_mode