IJ07980: JAVA SLOWDOWN DUE TO REPEATED MONITOR RESERVATION/CANCELLATION

APAR status

• Closed as program error.

Error description

• Error Message: N/A
  .
  Stack Trace: N/A
  .
  Performance degrades after upgrading Java from version 8 through
  8 SR4 FP11, to version 8 SR5 through 8 SR5 FP17. This only
  occurs on x86 and POWER platforms, and only when the application
  shares instances of StringBuffer or Random amongst threads.
  

Local fix

• It is possible to work around the issue by passing
  -Xjit:disableLockReservation on the command line.
  

Problem summary

• The JVM has a feature called lock reservation, which allows the
  JIT compiler to avoid expensive locked memory accesses when
  synchronizing on objects of particular types. The drawback is
  that if one thread reserves an object's monitor, and a second
  thread later attempts to lock the same monitor, the latter
  thread must cancel the reservation, which involves waiting for
  the former thread to pause. Furthermore, certain usage patterns
  can cause a monitor to undergo a cycle of repeated reservation
  and cancellation. Starting in Java 8 SR5, the JVM makes use of
  lock reservation by default for all StringBuffer and Random
  objects locked by calling a synchronized method.
  

Problem conclusion

• The JVM has been modified so that on x86 it will not reserve a
  monitor that has already had a reservation canceled.
  Unfortunately, this problem can still occur on POWER as of Java
  8 SR5 FP20.
  .
  This APAR will be fixed in the following Java Releases:
     8    SR5 FP20  (8.0.5.20)
  .
  Contact your IBM Product's Service Team for these Service
  Refreshes and Fix Packs.
  For those running stand-alone, information about the available
  Service Refreshes and Fix Packs can be found at:
             https://www.ibm.com/developerworks/java/jdk/
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Fix information

• Fixed component name

  JIT

• Fixed component ID

  620700124

Applicable component levels