Thu, 22 Sep 2011 10:57:37 -0700
6484982: G1: process references during evacuation pauses
Summary: G1 now uses two reference processors - one is used by concurrent marking and the other is used by STW GCs (both full and incremental evacuation pauses). In an evacuation pause, the reference processor is embedded into the closures used to scan objects. Doing so causes causes reference objects to be 'discovered' by the reference processor. At the end of the evacuation pause, these discovered reference objects are processed - preserving (and copying) referent objects (and their reachable graphs) as appropriate.
Reviewed-by: ysr, jwilhelm, brutisso, stefank, tonyp
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25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_COLLECTIONSETCHOOSER_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_G1_COLLECTIONSETCHOOSER_HPP
28 #include "gc_implementation/g1/heapRegion.hpp"
29 #include "utilities/growableArray.hpp"
31 // We need to sort heap regions by collection desirability.
33 class CSetChooserCache VALUE_OBJ_CLASS_SPEC {
34 private:
35 enum {
36 CacheLength = 16
37 } PrivateConstants;
39 HeapRegion* _cache[CacheLength];
40 int _occupancy; // number of region in cache
41 int _first; // "first" region in the cache
43 // adding CacheLength to deal with negative values
44 inline int trim_index(int index) {
45 return (index + CacheLength) % CacheLength;
46 }
48 inline int get_sort_index(int index) {
49 return -index-2;
50 }
51 inline int get_index(int sort_index) {
52 return -sort_index-2;
53 }
55 public:
56 CSetChooserCache(void);
58 inline int occupancy(void) { return _occupancy; }
59 inline bool is_full() { return _occupancy == CacheLength; }
60 inline bool is_empty() { return _occupancy == 0; }
62 void clear(void);
63 void insert(HeapRegion *hr);
64 HeapRegion *remove_first(void);
65 void remove (HeapRegion *hr);
66 inline HeapRegion *get_first(void) {
67 return _cache[_first];
68 }
70 #ifndef PRODUCT
71 bool verify (void);
72 bool region_in_cache(HeapRegion *hr) {
73 int sort_index = hr->sort_index();
74 if (sort_index < -1) {
75 int index = get_index(sort_index);
76 guarantee(index < CacheLength, "should be within bounds");
77 return _cache[index] == hr;
78 } else
79 return 0;
80 }
81 #endif // PRODUCT
82 };
84 class CollectionSetChooser: public CHeapObj {
86 GrowableArray<HeapRegion*> _markedRegions;
87 int _curMarkedIndex;
88 int _numMarkedRegions;
89 CSetChooserCache _cache;
91 // True iff last collection pause ran of out new "age 0" regions, and
92 // returned an "age 1" region.
93 bool _unmarked_age_1_returned_as_new;
95 jint _first_par_unreserved_idx;
97 public:
99 HeapRegion* getNextMarkedRegion(double time_so_far, double avg_prediction);
101 CollectionSetChooser();
103 void sortMarkedHeapRegions();
104 void fillCache();
105 bool addRegionToCache(void);
106 void addMarkedHeapRegion(HeapRegion *hr);
108 // Must be called before calls to getParMarkedHeapRegionChunk.
109 // "n_regions" is the number of regions, "chunkSize" the chunk size.
110 void prepareForAddMarkedHeapRegionsPar(size_t n_regions, size_t chunkSize);
111 // Returns the first index in a contiguous chunk of "n_regions" indexes
112 // that the calling thread has reserved. These must be set by the
113 // calling thread using "setMarkedHeapRegion" (to NULL if necessary).
114 jint getParMarkedHeapRegionChunk(jint n_regions);
115 // Set the marked array entry at index to hr. Careful to claim the index
116 // first if in parallel.
117 void setMarkedHeapRegion(jint index, HeapRegion* hr);
118 // Atomically increment the number of claimed regions by "inc_by".
119 void incNumMarkedHeapRegions(jint inc_by);
121 void clearMarkedHeapRegions();
123 void updateAfterFullCollection();
125 // Ensure that "hr" is not a member of the marked region array or the cache
126 void removeRegion(HeapRegion* hr);
128 bool unmarked_age_1_returned_as_new() { return _unmarked_age_1_returned_as_new; }
130 // Returns true if the used portion of "_markedRegions" is properly
131 // sorted, otherwise asserts false.
132 #ifndef PRODUCT
133 bool verify(void);
134 bool regionProperlyOrdered(HeapRegion* r) {
135 int si = r->sort_index();
136 return (si == -1) ||
137 (si > -1 && _markedRegions.at(si) == r) ||
138 (si < -1 && _cache.region_in_cache(r));
139 }
140 #endif
142 };
144 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_COLLECTIONSETCHOOSER_HPP