Priority mapping and inheritance

Each Java™ priority is mapped to an associated operating system base priority, and each operating system priority is associated with a scheduling policy. The WebSphere® Real Time for AIX® on 32-bit POWER® Linux® operating system scheduling policies are SCHED_OTHER, SCHED_RR and SCHED_FIFO.

Real-time Java threads use policy SCHED_FIFO, while regular Java threads use the policy of the thread that starts the JVM. The default scheduling policy for regular Java threads is SCHED_OTHER, but you can use a utility like chrt to set policies SCHED_RR or SCHED_FIFO. For more information about thread priorities and policies, see Thread scheduling and dispatching.

The following table shows how the Java priorities are mapped to native operating system priorities. Some Java priorities are reserved for use by the JVM, and some native priorities that have no corresponding Java priorities are used by the JVM as well.

Note:
User base priorities:
Java priorities 1-10: SCHED_OTHER, OS priority 0

Java priority 11: SCHED_FIFO, OS priority 25
Java priority 12: SCHED_FIFO, OS priority 27
Java priority 13: SCHED_FIFO, OS priority 29
Java priority 14: SCHED_FIFO, OS priority 31
Java priority 15: SCHED_FIFO, OS priority 33
Java priority 16: SCHED_FIFO, OS priority 35
Java priority 17: SCHED_FIFO, OS priority 37
Java priority 18: SCHED_FIFO, OS priority 39
Java priority 19: SCHED_FIFO, OS priority 41
Java priority 20: SCHED_FIFO, OS priority 43
Java priority 21: SCHED_FIFO, OS priority 45
Java priority 22: SCHED_FIFO, OS priority 47
Java priority 23: SCHED_FIFO, OS priority 49
Java priority 24: SCHED_FIFO, OS priority 51
Java priority 25: SCHED_FIFO, OS priority 53
Java priority 26: SCHED_FIFO, OS priority 55
Java priority 27: SCHED_FIFO, OS priority 57
Java priority 28: SCHED_FIFO, OS priority 59
Java priority 29: SCHED_FIFO, OS priority 61
Java priority 30: SCHED_FIFO, OS priority 63
Java priority 31: SCHED_FIFO, OS priority 65
Java priority 32: SCHED_FIFO, OS priority 67
Java priority 33: SCHED_FIFO, OS priority 69
Java priority 34: SCHED_FIFO, OS priority 71
Java priority 35: SCHED_FIFO, OS priority 73
Java priority 36: SCHED_FIFO, OS priority 75
Java priority 37: SCHED_FIFO, OS priority 77
Java priority 38: SCHED_FIFO, OS priority 79
Internal base priorities:
Internal Java priority 39: SCHED_FIFO, OS priority 81
Internal Java priority 40: SCHED_FIFO, OS priority 83
Internal Java priority 41: SCHED_FIFO, OS priority 84
Internal Java priority 42: SCHED_FIFO, OS priority 85
Internal Java priority 43: SCHED_FIFO, OS priority 86
Internal Java priority 44: SCHED_FIFO, OS priority 87
Internal Java priority 45: SCHED_FIFO, OS priority 88
OS priorities 11, 12, 13
OS priorities even numbers 26, 28, 30, ..., 82
OS priority 89

See also: the "Synchronization" section in .



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