phoneME advanced Garbage Collector

一、Build Options

-CVM_GCCHOICE (Generational/marksweep/semispace)
Default: generational
Example:-CVM_GCCHOICE=semispace

二、Runtime Options
-Xgc:gc_specific_options(In generational is youngGen=nnn in bytes)
Default: 1M

-Xmssize (memory allocation pool)
Default: 4M
Example: -Xms6291456, -Xms6144k, -Xms6m

三、Source Organization

• src/share/javavm/include/gc_common.h：The shared GC interface.
• src/share/javavm/include/gc/gc_impl.h ：The gcimpl GC interface that has to be implemented for each GC.
• src/share/javavm/include/gc//gc_config.h ：The configuration file for a specific GC.
• src/share/javavm/runtime/gc//gc_impl.c ：The implementation file for a specific GC.
  

四、Execution Flow

1. CVM allocates memory using the shared routine CVMgcAllocNewInstance().
2. CVMgcAllocNewInstance() does some processing and calls the GC-specific
   CVMgcimplAllocObject() to allocate the actual space for the object.
3. CVMgcimplAllocObject() performs the GC and calls the shared routine
   CVMgcStopTheWorldAndGC() to stop all threads at GC-safe points.
4. CVMgcStopTheWorldAndGC() ensures that all threads rendezvous at GC-safe points. When that is done, it calls the GC implementation CVMgcimplDoGC() to perform the GC action.
5. CVMgcimplDoGC() may call shared GC service routines to scan GC state: For example, CVMgcScanRoots() to scan all roots or CVMobjectWalkRefs() to scan the pointers in a given object or array.
6. When CVMgcimplDoGC() returns, all threads that were stopped at GC points resume execution. Eventually, CVMgcAllocNewInstance() returns and the thread that originally initiated GC resumes execution.
   
   
   

五、測試

make clean; (win32 makefile有問題)
make CVM_GCCHOICE=[semispacegenerationalmarksweep]
bin/cvm -cp testclasses.zip HelloWorld;
bin/cvm -XshowBuildOptions;

六、reference

CDCfoundation_porting_guide.pdf