JDK-6652736 : well known classes in system dictionary are inefficiently processed
  • Type: Bug
  • Component: hotspot
  • Sub-Component: runtime
  • Affected Version: 7
  • Priority: P3
  • Status: Closed
  • Resolution: Fixed
  • OS: generic
  • CPU: generic
  • Submitted: 2008-01-19
  • Updated: 2012-10-08
  • Resolved: 2008-07-01
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JDK 6 JDK 7 Other
6u4Fixed 7Fixed hs10Fixed
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Description
The SystemDictionary class has about 60 C static variables which hold well-known classes.  They should be consolidated into a single static block of C array-type, indexed by an enum, as in vmSymbols.  This will simplify maintenance and scaling and allow certain optimizations.

At JVM bootstrap, approximately 25% of all symbol lookups resolve to these symbols.  It is probably worthwhile making a fast path for these (using vmSymbols::find_sid).

The object code which operates on these classes as a group (for GC and initialization) will be much more compact if they are made into an array indexed by an enum.  Several object files are smaller by 1-10Kb, including systemDictionary.o, vmStructs.o, javaClasses.o, and jvm.o, and the DLL is about 40Kb smaller.

The number of well-known classes will increase as new low-level features are added to support other languages.  Adding them should be as simple as adding new vmSymbols.

Benefits:
 - fewer symbols in the binary
 - code simplification
 - a fast path through the class lookup routine
 - easier expansion in the future

Comments
EVALUATION Yes.
01-07-2008

SUGGESTED FIX webrev forthcoming; temporary location is http://homepage.mac.com/rose00/work/webrev/README.htm *** (#1 of 1): [ UNSAVED ] ###@###.###
19-01-2008