Interface VirtualThreadSchedulerMXBean

All Superinterfaces:
PlatformManagedObject
public interface VirtualThreadSchedulerMXBean extends PlatformManagedObject
Management interface for the JDK's virtual thread scheduler.

VirtualThreadSchedulerMXBean supports monitoring of the virtual thread scheduler's target parallelism, the platform threads used by the scheduler, and the number of virtual threads queued to the scheduler. It also supports dynamically changing the scheduler's target parallelism.

The management interface is registered with the platform MBeanServer. The ObjectName that uniquely identifies the management interface within the MBeanServer is: "jdk.management:type=VirtualThreadScheduler".

Direct access to the MXBean interface can be obtained with ManagementFactory.getPlatformMXBean(Class).

Since:
24

  • Method Summary

    Modifier and Type
    Method
    Description
    int
    getMountedVirtualThreadCount()
    Returns an estimate of the number of virtual threads that are currently mounted by the scheduler; -1 if not known.
    int
    getParallelism()
    Returns the scheduler's target parallelism.
    int
    getPoolSize()
    Returns the current number of platform threads that the scheduler has started but have not terminated; -1 if not known.
    long
    getQueuedVirtualThreadCount()
    Returns an estimate of the number of virtual threads that are queued to the scheduler to start or continue execution; -1 if not known.
    void
    setParallelism(int size)
    Sets the scheduler's target parallelism.

    Methods declared in interface java.lang.management.PlatformManagedObject

    getObjectName

  • Method Details

    • getParallelism

      int getParallelism()
      Returns the scheduler's target parallelism.
      Returns:
      the scheduler's target parallelism
      See Also:

    • setParallelism

      void setParallelism(int size)
      Sets the scheduler's target parallelism.

      Increasing the target parallelism allows the scheduler to use more platform threads to carry virtual threads if required. Decreasing the target parallelism reduces the number of threads that the scheduler may use to carry virtual threads.

      API Note:
      If virtual threads are mounting and unmounting frequently then downward adjustment of the target parallelism will likely come into effect quickly.
      Implementation Note:
      The JDK's virtual thread scheduler is a ForkJoinPool. Target parallelism defaults to the number of available processors. The minimum target parallelism is 1, the maximum target parallelism is 32767.
      Parameters:
      size - the target parallelism level
      Throws:
      IllegalArgumentException - if size is less than the minimum, or greater than the maximum, supported by the scheduler
      UnsupportedOperationException - if changing the target parallelism is not suppored by the scheduler
      See Also:

    • getPoolSize

      int getPoolSize()
      Returns the current number of platform threads that the scheduler has started but have not terminated; -1 if not known.

      The count includes the platform threads that are currently carrying virtual threads and the platform threads that are not currently carrying virtual threads. The thread count may be greater than the scheduler's target parallelism.

      Implementation Note:
      The JDK's virtual thread scheduler is a ForkJoinPool. The pool size is the number of worker threads.
      Returns:
      the current number of platform threads that the scheduler has started but have not terminated; -1 if not known

    • getMountedVirtualThreadCount

      int getMountedVirtualThreadCount()
      Returns an estimate of the number of virtual threads that are currently mounted by the scheduler; -1 if not known.

      The number of mounted virtual threads is equal to the number of platform threads carrying virtual threads.

      Implementation Note:
      This method may overestimate the number of virtual threads that are mounted.
      Returns:
      an estimate of the number of virtual threads that are currently mounted by the scheduler; -1 if not known

    • getQueuedVirtualThreadCount

      long getQueuedVirtualThreadCount()
      Returns an estimate of the number of virtual threads that are queued to the scheduler to start or continue execution; -1 if not known.
      Implementation Note:
      This method may overestimate the number of virtual threads that are queued to execute.
      Returns:
      an estimate of the number of virtual threads that are queued to the scheduler to start or continue execution; -1 if not known