IV59515: PERFORMANCE DEGRADATION FROM JAVA 7.0 TO JAVA 7.1 ON X86

APAR status

• Closed as program error.

Error description

• Error Message: N/A
  .
  Stack Trace: N/A
  .
  After migrating from Java 7.0 to Java 7.1, a reduction in
  throughput is observed while running certain types of WebSphere
  applications on X86 systems.
  

Local fix

• Setting the environment variables TR_AlignInstanceSize=999999
  and TR_disableInlinedNT=1 might help avoid the performance
  degradation. These variables are independent of each other and
  can be tried separately.
  

Problem summary

• There were two issues with Just-In-Time (JIT) compilation on X86
  hardware.First, an optimization added padding when between
  allocated objects to prevent them from straddling cache-line
  boundaries, but the padding consumes extra memory and cache
  lines, so it is not always beneficial. This issue affected both
  Windows and x86 Linux.Second, inconsistent logic in the
  optimization of the System.nanoTime method caused that method to
  be dispatched via the interpreter on Windows, which is much
  slower than a direct call.
  

Problem conclusion

• This APAR will be fixed in the following Java Releases:
     7 R1 SR1       (7.1.1.0)
  .
  First, the heap padding control logic was restricted so it
  occurs only when it is beneficial.Second, the nanoTime
  optimization was fixed so the method is called directly rather
  than though the interpreter.
  

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

• R130 PSY

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