Thu, 26 Jun 2014 11:36:58 +0200
8047818: G1 HeapRegions can no longer be ContiguousSpaces
Summary: Change parent of G1OffsetTableContigSpace to CompactibleSpace, reimplement missing functionality
Reviewed-by: stefank, jmasa, tschatzl
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25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGION_INLINE_HPP
26 #define SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGION_INLINE_HPP
28 #include "gc_implementation/g1/g1BlockOffsetTable.inline.hpp"
29 #include "gc_implementation/g1/g1CollectedHeap.hpp"
30 #include "gc_implementation/g1/heapRegion.hpp"
31 #include "memory/space.hpp"
32 #include "runtime/atomic.inline.hpp"
34 // This version requires locking.
35 inline HeapWord* G1OffsetTableContigSpace::allocate_impl(size_t size,
36 HeapWord* const end_value) {
37 HeapWord* obj = top();
38 if (pointer_delta(end_value, obj) >= size) {
39 HeapWord* new_top = obj + size;
40 set_top(new_top);
41 assert(is_aligned(obj) && is_aligned(new_top), "checking alignment");
42 return obj;
43 } else {
44 return NULL;
45 }
46 }
48 // This version is lock-free.
49 inline HeapWord* G1OffsetTableContigSpace::par_allocate_impl(size_t size,
50 HeapWord* const end_value) {
51 do {
52 HeapWord* obj = top();
53 if (pointer_delta(end_value, obj) >= size) {
54 HeapWord* new_top = obj + size;
55 HeapWord* result = (HeapWord*)Atomic::cmpxchg_ptr(new_top, top_addr(), obj);
56 // result can be one of two:
57 // the old top value: the exchange succeeded
58 // otherwise: the new value of the top is returned.
59 if (result == obj) {
60 assert(is_aligned(obj) && is_aligned(new_top), "checking alignment");
61 return obj;
62 }
63 } else {
64 return NULL;
65 }
66 } while (true);
67 }
69 inline HeapWord* G1OffsetTableContigSpace::allocate(size_t size) {
70 HeapWord* res = allocate_impl(size, end());
71 if (res != NULL) {
72 _offsets.alloc_block(res, size);
73 }
74 return res;
75 }
77 // Because of the requirement of keeping "_offsets" up to date with the
78 // allocations, we sequentialize these with a lock. Therefore, best if
79 // this is used for larger LAB allocations only.
80 inline HeapWord* G1OffsetTableContigSpace::par_allocate(size_t size) {
81 MutexLocker x(&_par_alloc_lock);
82 return allocate(size);
83 }
85 inline HeapWord* G1OffsetTableContigSpace::block_start(const void* p) {
86 return _offsets.block_start(p);
87 }
89 inline HeapWord*
90 G1OffsetTableContigSpace::block_start_const(const void* p) const {
91 return _offsets.block_start_const(p);
92 }
94 inline bool
95 HeapRegion::block_is_obj(const HeapWord* p) const {
96 return p < top();
97 }
99 inline size_t
100 HeapRegion::block_size(const HeapWord *addr) const {
101 const HeapWord* current_top = top();
102 if (addr < current_top) {
103 return oop(addr)->size();
104 } else {
105 assert(addr == current_top, "just checking");
106 return pointer_delta(end(), addr);
107 }
108 }
110 inline HeapWord* HeapRegion::par_allocate_no_bot_updates(size_t word_size) {
111 assert(is_young(), "we can only skip BOT updates on young regions");
112 return par_allocate_impl(word_size, end());
113 }
115 inline HeapWord* HeapRegion::allocate_no_bot_updates(size_t word_size) {
116 assert(is_young(), "we can only skip BOT updates on young regions");
117 return allocate_impl(word_size, end());
118 }
120 inline void HeapRegion::note_start_of_marking() {
121 _next_marked_bytes = 0;
122 _next_top_at_mark_start = top();
123 }
125 inline void HeapRegion::note_end_of_marking() {
126 _prev_top_at_mark_start = _next_top_at_mark_start;
127 _prev_marked_bytes = _next_marked_bytes;
128 _next_marked_bytes = 0;
130 assert(_prev_marked_bytes <=
131 (size_t) pointer_delta(prev_top_at_mark_start(), bottom()) *
132 HeapWordSize, "invariant");
133 }
135 inline void HeapRegion::note_start_of_copying(bool during_initial_mark) {
136 if (is_survivor()) {
137 // This is how we always allocate survivors.
138 assert(_next_top_at_mark_start == bottom(), "invariant");
139 } else {
140 if (during_initial_mark) {
141 // During initial-mark we'll explicitly mark any objects on old
142 // regions that are pointed to by roots. Given that explicit
143 // marks only make sense under NTAMS it'd be nice if we could
144 // check that condition if we wanted to. Given that we don't
145 // know where the top of this region will end up, we simply set
146 // NTAMS to the end of the region so all marks will be below
147 // NTAMS. We'll set it to the actual top when we retire this region.
148 _next_top_at_mark_start = end();
149 } else {
150 // We could have re-used this old region as to-space over a
151 // couple of GCs since the start of the concurrent marking
152 // cycle. This means that [bottom,NTAMS) will contain objects
153 // copied up to and including initial-mark and [NTAMS, top)
154 // will contain objects copied during the concurrent marking cycle.
155 assert(top() >= _next_top_at_mark_start, "invariant");
156 }
157 }
158 }
160 inline void HeapRegion::note_end_of_copying(bool during_initial_mark) {
161 if (is_survivor()) {
162 // This is how we always allocate survivors.
163 assert(_next_top_at_mark_start == bottom(), "invariant");
164 } else {
165 if (during_initial_mark) {
166 // See the comment for note_start_of_copying() for the details
167 // on this.
168 assert(_next_top_at_mark_start == end(), "pre-condition");
169 _next_top_at_mark_start = top();
170 } else {
171 // See the comment for note_start_of_copying() for the details
172 // on this.
173 assert(top() >= _next_top_at_mark_start, "invariant");
174 }
175 }
176 }
178 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGION_INLINE_HPP