Tue, 19 Aug 2014 02:05:49 -0700
8044406: JVM crash with JDK8 (build 1.8.0-b132) with G1 GC
Summary: Fill the last card that has been allocated into with a dummy object
Reviewed-by: tschatzl, mgerdin
1 /*
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25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP
28 #include "gc_implementation/g1/g1BiasedArray.hpp"
30 class HeapRegion;
31 class HeapRegionClosure;
32 class FreeRegionList;
34 class G1HeapRegionTable : public G1BiasedMappedArray<HeapRegion*> {
35 protected:
36 virtual HeapRegion* default_value() const { return NULL; }
37 };
39 // This class keeps track of the region metadata (i.e., HeapRegion
40 // instances). They are kept in the _regions array in address
41 // order. A region's index in the array corresponds to its index in
42 // the heap (i.e., 0 is the region at the bottom of the heap, 1 is
43 // the one after it, etc.). Two regions that are consecutive in the
44 // array should also be adjacent in the address space (i.e.,
45 // region(i).end() == region(i+1).bottom().
46 //
47 // We create a HeapRegion when we commit the region's address space
48 // for the first time. When we uncommit the address space of a
49 // region we retain the HeapRegion to be able to re-use it in the
50 // future (in case we recommit it).
51 //
52 // We keep track of three lengths:
53 //
54 // * _committed_length (returned by length()) is the number of currently
55 // committed regions.
56 // * _allocated_length (not exposed outside this class) is the
57 // number of regions for which we have HeapRegions.
58 // * max_length() returns the maximum number of regions the heap can have.
59 //
60 // and maintain that: _committed_length <= _allocated_length <= max_length()
62 class HeapRegionSeq: public CHeapObj<mtGC> {
63 friend class VMStructs;
65 G1HeapRegionTable _regions;
67 // The number of regions committed in the heap.
68 uint _committed_length;
70 // A hint for which index to start searching from for humongous
71 // allocations.
72 uint _next_search_index;
74 // The number of regions for which we have allocated HeapRegions for.
75 uint _allocated_length;
77 // Find a contiguous set of empty regions of length num, starting
78 // from the given index.
79 uint find_contiguous_from(uint from, uint num);
81 void increment_allocated_length() {
82 assert(_allocated_length < max_length(), "pre-condition");
83 _allocated_length++;
84 }
86 void increment_length() {
87 assert(length() < max_length(), "pre-condition");
88 _committed_length++;
89 }
91 void decrement_length() {
92 assert(length() > 0, "pre-condition");
93 _committed_length--;
94 }
96 HeapWord* heap_bottom() const { return _regions.bottom_address_mapped(); }
97 HeapWord* heap_end() const {return _regions.end_address_mapped(); }
99 public:
100 // Empty contructor, we'll initialize it with the initialize() method.
101 HeapRegionSeq() : _regions(), _committed_length(0), _next_search_index(0), _allocated_length(0) { }
103 void initialize(HeapWord* bottom, HeapWord* end);
105 // Return the HeapRegion at the given index. Assume that the index
106 // is valid.
107 inline HeapRegion* at(uint index) const;
109 // If addr is within the committed space return its corresponding
110 // HeapRegion, otherwise return NULL.
111 inline HeapRegion* addr_to_region(HeapWord* addr) const;
113 // Return the HeapRegion that corresponds to the given
114 // address. Assume the address is valid.
115 inline HeapRegion* addr_to_region_unsafe(HeapWord* addr) const;
117 // Return the number of regions that have been committed in the heap.
118 uint length() const { return _committed_length; }
120 // Return the maximum number of regions in the heap.
121 uint max_length() const { return (uint)_regions.length(); }
123 // Expand the sequence to reflect that the heap has grown from
124 // old_end to new_end. Either create new HeapRegions, or re-use
125 // existing ones, and return them in the given list. Returns the
126 // memory region that covers the newly-created regions. If a
127 // HeapRegion allocation fails, the result memory region might be
128 // smaller than the desired one.
129 MemRegion expand_by(HeapWord* old_end, HeapWord* new_end,
130 FreeRegionList* list);
132 // Return the number of contiguous regions at the end of the sequence
133 // that are available for allocation.
134 uint free_suffix();
136 // Find a contiguous set of empty regions of length num and return
137 // the index of the first region or G1_NULL_HRS_INDEX if the
138 // search was unsuccessful.
139 uint find_contiguous(uint num);
141 // Apply blk->doHeapRegion() on all committed regions in address order,
142 // terminating the iteration early if doHeapRegion() returns true.
143 void iterate(HeapRegionClosure* blk) const;
145 // As above, but start the iteration from hr and loop around. If hr
146 // is NULL, we start from the first region in the heap.
147 void iterate_from(HeapRegion* hr, HeapRegionClosure* blk) const;
149 // Tag as uncommitted as many regions that are completely free as
150 // possible, up to num_regions_to_remove, from the suffix of the committed
151 // sequence. Return the actual number of removed regions.
152 uint shrink_by(uint num_regions_to_remove);
154 // Do some sanity checking.
155 void verify_optional() PRODUCT_RETURN;
156 };
158 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP