| pm.max_children | the maximum number of children that can be alive at the same time |
| pm.start_servers | the number of children created on startup |
| pm.min_spare_servers | the minimum number of children in 'idle' state (waiting to process). If the number of 'idle' processes is less than this number then some children will be created |
| pm.max_spare_servers | the maximum number of children in 'idle' state (waiting to process). If the number of 'idle' processes is greater than this number then some children will be killed |
| pm.max_spawn_rate | the maximum number of rate to spawn child processes at once |