IV19920: JAVA JIT - RARE PERFORMANCE PROBLEM WITH LARGE APPLICATIONS

APAR status

• Closed as program error.

Error description

• Error Message: JVM slows after a executing for a long time
  without a problem.
  .
  Stack Trace: N/A
  .
  The application needs to be large enough to run into the JIT
  code cache limit. The performance problem will only be
  noticeable in applications executing the same code on several
  threads.
  The performance problem is very hard to hit and it will be
  nearly impossible for customers to hit the problem for a second
  time.
  

Local fix

• The problem can be avoided by using the following Java command
  line option:
  -Xjit:disableProfiling
  This option will have a negative effect on performance, but not
  to the same extent as is seen when the this problem occurs.
  

Problem summary

• For hot methods the JIT will generate a "profiling" JIT compiled
  body. The execution of this body collects profiling information
  that is used later when we recompile the method. If we exhaust
  the JIT code cache before the recompile happens we end up being
  stuck executing a profiled body which, under some circumstances
  can have a major performance impact.
  

Problem conclusion

• This defect will be fixed in:
  6.0.1 SR2
  7.0.0 SR1
  .
  The JIT will avoid making profiled bodies when we are close to
  running out of JIT code cache space.
  

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

• R260 PSY

     UP