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docs/Garbage-Collector.md

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+TODO: notes on how cyclone's GC works
+
+terms: mutators, collector, what else?
+
+two types:
+
+- minor GC (stack portion from Cheney on MTA)
+- major GC - Doligez-Leroy-Gonthier (DLG) collector
+
+motivations: 
+- extend baker's approach to support multiple mutators
+- State of the art GC's are built on top of DLG (stopless, chicken, clover)
+
+limitations or potential issues:
+- DLG memory fragmentation could be an issue for long-running programs
+
+## minor GC
+
+changes from Cheney on MTA:
+- each thread has its own stack
+
+## major GC
+
+overview from paper
+
+- single collector thread, multiple mutator threads
+- single heap
+- generally try to use atomic operations, but there is some locking. In particular, heap is protected by lock during object allocation / deallocation
+
+GC stages / status:
+/* Enums for tri-color marking */
+typedef enum { STATUS_ASYNC 
+             , STATUS_SYNC1 
+             , STATUS_SYNC2 
+             } gc_status_type;
+
+typedef enum { STAGE_CLEAR_OR_MARKING 
+             , STAGE_TRACING 
+             //, STAGE_REF_PROCESSING 
+             , STAGE_SWEEPING 
+             , STAGE_RESTING
+             } gc_stage_type;
+
+object colors:
+red
+blue
+white
+gray
+black
+
+
+important to explain how minor/major algorithms are interleaved. EG:
+
+thread states:
+typedef enum { CYC_THREAD_STATE_NEW
+             , CYC_THREAD_STATE_RUNNABLE
+             , CYC_THREAD_STATE_BLOCKED
+             , CYC_THREAD_STATE_BLOCKED_COOPERATING
+             , CYC_THREAD_STATE_TERMINATED
+             } cyc_thread_state_type;
+
+typedef struct gc_thread_data_t gc_thread_data;
+
+ETC