[rvm-research] Questions after reading SemiSpace Plan

Hello All,

I have several questions about the SemiSpaceCollector:
1.colletionPhase()
SS, SSCollector & SSMutator all have the"collectionPhase()"method, but they are different.
Which class and when call these 3 collectionPhase()? The host VM call them??

How to arrange phases in collectionPhase()? Although they may have same phaseID, but call different methods.
For example, SSCollector rebinds ss(CopyLocal) to ToSpace at  SS.PREPARE, while SSMutator  rebinds ss to ToSpace at  SS.RELEASE.

2.SSTraceLocal.traceObject()
Which class and when call SSTraceLocal.traceObject()? SSTraceLocal.traceObject() calls the CopySpace.traceObject().
I recognized that 

SSCollector.collectionPhase(){if(phaseID==SS.CLOSURE){trace.completeTrace();}}, 

this will call the TraceLocal.completeTrace() to finish processing all GC work.
The methodprocessRoots() → processRootEdge() → traceObeject(object,root) → traceObject(object)
→ traceObject(VMSpace/ImmortalSpace/...[but no CopySpace],object).
The method scanObject()→VM.scanning.specializedScanObject()  or VM.scanning.scanObject(). 

I'm wondering whetherVM.scanning.specializedScanObject() will call SSTraceLocal.traceObject()?

3.Constraints
What needs to be written into Constraints?
I just know numSpecializedScans().


4.CopySpace
The initialization of CopySpace depends on vmRequest, whether vmRequest.isDiscontiguous() has a effect on collector's performance?

5.Flip
SS.collectionPhase(){if(phaseID==SS.RELEASE){fromSpace().release();}}
This method calls CopySpace.release(),make the FromSpace become Non-FromSpace(Does this mean it becomes a ToSpace?). 

But when and where ToSpace becomes FromSpace?
SS.collectionPhase(){if(phaseID==SS.PREPARE){hi=!hi;}}
I guess after a collection allocator allocates objects into ToSpace(in last GC)/Nursery untill it's full, trigger a new collction.
Now SS.PREPARE, flip the Nursery/ToSpace(in last GC) to FromSpace, FromSpace(in last GC) becomes the ToSpace.Am I right?



6.How to under stand the components of a collector woks together?
I thinks that's the reason why I feel confused about some questions above. Any suggestions?

Thanks for any help.
Best Wishes.
                                                                                    Chen Hao

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