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Some note about GC algorithm
- 3. Somefunfacts
- 10. It'sfuckinghard
- 17. markingphase markFromRoots(): initialise(worklist) for each fld in Roots ref ← *fld if ref ≠ null && not isMarked(ref) setMarked(ref) add(worklist, ref) mark() initialise(worklist): worklist ← empty mark(): while not isEmpty(worklist) ref ← remove(worklist) /* ref is marked */ for each fld in Pointers (ref) child ← *fld if child ≠ null && not isMarked(child) setMarked(child) add(worklist, child)
- 18. sweepingphase sweep(start, end): scan ← start while scan < end if isMarked(scan) unsetMarked(scan) else free(scan) scan ← nextObject(scan)
- 22. minigcgc void garbage_collect(void) { size_t i; /* marking machine context */ gc_mark_register(); gc_mark_stack(); /* marking roots */ for (i = 0; i < root_ranges_used; i++) { gc_mark_range(root_ranges[i].start, root_ranges[i].end) } /* sweeping */ gc_sweep(); }
- 23. markregister:markeverythingincurrentcontext usingsetjmp static void gc_mark_register(void) { jmp_buf env; size_t i; setjmp(env); for (i = 0; i < sizeof(env); i++) { gc_mark(((void **)env)[i]); } }
- 24. markstack:markfromstartofstacktoendofstack static void gc_mark_stack(void) { set_stack_end(); if (stack_start > stack_end) { gc_mark_range(stack_end, stack_start); } else { gc_mark_range(stack_start, stack_end); } }
- 25. markingusingheaderbitset static void gc_mark(void * ptr) { GC_Heap *gh; Header *hdr; /* mark check */ if (!(gh = is_pointer_to_heap(ptr))) return; if (!(hdr = get_header(gh, ptr))) return; if (!FL_TEST(hdr, FL_ALLOC)) return; if (FL_TEST(hdr, FL_MARK)) return; /* marking */ FL_SET(hdr, FL_MARK); DEBUG(printf("mark ptr : %p, header : %pn", ptr, hdr)); /* mark children */ gc_mark_range((void *)(hdr+1), (void *)NEXT_HEADER(hdr)); }