IV67003: LOCK CONTENTION CAUSES POOR PERFORMANCE FOR CLASS.GETANNOTATIONS

APAR status

• Closed as program error.

Error description

• Error Message: N/A
  .
  Stack Trace: For example:Java
  callstack:java/util/Hashtable.get(Hashtable.javajava/lang/Class.
  getDeclaredAnnotationsjava/lang/Class.getAnnotationsjava/lang/Cl
  ass.getAnnotation
  .
  Javacore will show contention over a hashtable lock:2LKMONINUSE
      sys_mon_t:0x0000000023796A10 infl_mon_t:
  0x0000000023796A80:3LKMONOBJECT
  java/util/Hashtable@0x0000000082CD7998/0x0000000082CD79A4: owner
  "Thread-238" (0x0000000004305300), entry count 13LKWAITERQ
       Waiting to enter:3LKWAITER                "Thread-65"
  (0x0000000004A67D00)3LKWAITER                "Thread-66"
  (0x0000000004A68D00)3LKWAITER                "Thread-67"
  (0x0000000004A69E00)
  

Local fix

Problem summary

• The implementation of Class.getDeclaredAnnotations() (and
  methods which call this) relied on a hashtable lock. If many
  threads are using the Annotation methods, poor application
  performance can result, as the threads will all be contending
  for the same lock.
  

Problem conclusion

• The implementation of the Class.getDeclaredAnnotations() no
  longer relies on a hashtable lock, clearing this potential
  bottleneck.
  .
  This APAR will be fixed in the following Java Releases:
     6    SR16 FP3  (6.0.16.3)
     7 R1 SR2 FP10  (7.1.2.10)
     6 R1 SR8 FP3   (6.1.8.3)
     7    SR8 FP10  (7.0.8.10)
  .
  Contact your IBM Product's Service Team for these Service
  Refreshes and Fix Packs.
  For those running stand-alone, information about the 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

  J9 COMMON CODE

• Fixed component ID

  620700127

Applicable component levels

• R600 PSY

     UP

• R270 PSY

     UP

• R260 PSY

     UP