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24
25#ifndef SHARE_GC_G1_HEAPREGIONMANAGER_HPP
26#define SHARE_GC_G1_HEAPREGIONMANAGER_HPP
27
28#include "gc/g1/g1BiasedArray.hpp"
29#include "gc/g1/g1RegionToSpaceMapper.hpp"
30#include "gc/g1/heapRegionSet.hpp"
31#include "services/memoryUsage.hpp"
32
33class HeapRegion;
34class HeapRegionClosure;
35class HeapRegionClaimer;
36class FreeRegionList;
37class WorkGang;
38
39class G1HeapRegionTable : public G1BiasedMappedArray<HeapRegion*> {
40 protected:
41 virtual HeapRegion* default_value() const { return NULL; }
42};
43
44// This class keeps track of the actual heap memory, auxiliary data
45// and its metadata (i.e., HeapRegion instances) and the list of free regions.
46//
47// This allows maximum flexibility for deciding what to commit or uncommit given
48// a request from outside.
49//
50// HeapRegions are kept in the _regions array in address order. A region's
51// index in the array corresponds to its index in the heap (i.e., 0 is the
52// region at the bottom of the heap, 1 is the one after it, etc.). Two
53// regions that are consecutive in the array should also be adjacent in the
54// address space (i.e., region(i).end() == region(i+1).bottom().
55//
56// We create a HeapRegion when we commit the region's address space
57// for the first time. When we uncommit the address space of a
58// region we retain the HeapRegion to be able to re-use it in the
59// future (in case we recommit it).
60//
61// We keep track of three lengths:
62//
63// * _num_committed (returned by length()) is the number of currently
64// committed regions. These may not be contiguous.
65// * _allocated_heapregions_length (not exposed outside this class) is the
66// number of regions+1 for which we have HeapRegions.
67// * max_length() returns the maximum number of regions the heap can have.
68//
69
70class HeapRegionManager: public CHeapObj<mtGC> {
71 friend class VMStructs;
72 friend class HeapRegionClaimer;
73
74 G1RegionToSpaceMapper* _bot_mapper;
75 G1RegionToSpaceMapper* _cardtable_mapper;
76 G1RegionToSpaceMapper* _card_counts_mapper;
77
78 // Each bit in this bitmap indicates that the corresponding region is available
79 // for allocation.
80 CHeapBitMap _available_map;
81
82 // The number of regions committed in the heap.
83 uint _num_committed;
84
85 // Internal only. The highest heap region +1 we allocated a HeapRegion instance for.
86 uint _allocated_heapregions_length;
87
88 HeapWord* heap_bottom() const { return _regions.bottom_address_mapped(); }
89 HeapWord* heap_end() const {return _regions.end_address_mapped(); }
90
91 // Pass down commit calls to the VirtualSpace.
92 void commit_regions(uint index, size_t num_regions = 1, WorkGang* pretouch_gang = NULL);
93
94 // Notify other data structures about change in the heap layout.
95 void update_committed_space(HeapWord* old_end, HeapWord* new_end);
96
97 // Find a contiguous set of empty or uncommitted regions of length num and return
98 // the index of the first region or G1_NO_HRM_INDEX if the search was unsuccessful.
99 // If only_empty is true, only empty regions are considered.
100 // Searches from bottom to top of the heap, doing a first-fit.
101 uint find_contiguous(size_t num, bool only_empty);
102 // Finds the next sequence of unavailable regions starting from start_idx. Returns the
103 // length of the sequence found. If this result is zero, no such sequence could be found,
104 // otherwise res_idx indicates the start index of these regions.
105 uint find_unavailable_from_idx(uint start_idx, uint* res_idx) const;
106 // Finds the next sequence of empty regions starting from start_idx, going backwards in
107 // the heap. Returns the length of the sequence found. If this value is zero, no
108 // sequence could be found, otherwise res_idx contains the start index of this range.
109 uint find_empty_from_idx_reverse(uint start_idx, uint* res_idx) const;
110
111protected:
112 G1HeapRegionTable _regions;
113 G1RegionToSpaceMapper* _heap_mapper;
114 G1RegionToSpaceMapper* _prev_bitmap_mapper;
115 G1RegionToSpaceMapper* _next_bitmap_mapper;
116 FreeRegionList _free_list;
117
118 void make_regions_available(uint index, uint num_regions = 1, WorkGang* pretouch_gang = NULL);
119 void uncommit_regions(uint index, size_t num_regions = 1);
120 // Allocate a new HeapRegion for the given index.
121 HeapRegion* new_heap_region(uint hrm_index);
122#ifdef ASSERT
123public:
124 bool is_free(HeapRegion* hr) const;
125#endif
126public:
127 // Empty constructor, we'll initialize it with the initialize() method.
128 HeapRegionManager();
129
130 static HeapRegionManager* create_manager(G1CollectedHeap* heap);
131
132 virtual void initialize(G1RegionToSpaceMapper* heap_storage,
133 G1RegionToSpaceMapper* prev_bitmap,
134 G1RegionToSpaceMapper* next_bitmap,
135 G1RegionToSpaceMapper* bot,
136 G1RegionToSpaceMapper* cardtable,
137 G1RegionToSpaceMapper* card_counts);
138
139 // Prepare heap regions before and after full collection.
140 // Nothing to be done in this class.
141 virtual void prepare_for_full_collection_start() {}
142 virtual void prepare_for_full_collection_end() {}
143
144 // Return the "dummy" region used for G1AllocRegion. This is currently a hardwired
145 // new HeapRegion that owns HeapRegion at index 0. Since at the moment we commit
146 // the heap from the lowest address, this region (and its associated data
147 // structures) are available and we do not need to check further.
148 virtual HeapRegion* get_dummy_region() { return new_heap_region(0); }
149
150 // Return the HeapRegion at the given index. Assume that the index
151 // is valid.
152 inline HeapRegion* at(uint index) const;
153
154 // Return the HeapRegion at the given index, NULL if the index
155 // is for an unavailable region.
156 inline HeapRegion* at_or_null(uint index) const;
157
158 // Returns whether the given region is available for allocation.
159 bool is_available(uint region) const;
160
161 // Return the next region (by index) that is part of the same
162 // humongous object that hr is part of.
163 inline HeapRegion* next_region_in_humongous(HeapRegion* hr) const;
164
165 // If addr is within the committed space return its corresponding
166 // HeapRegion, otherwise return NULL.
167 inline HeapRegion* addr_to_region(HeapWord* addr) const;
168
169 // Insert the given region into the free region list.
170 inline void insert_into_free_list(HeapRegion* hr);
171
172 // Insert the given region list into the global free region list.
173 void insert_list_into_free_list(FreeRegionList* list) {
174 _free_list.add_ordered(list);
175 }
176
177 virtual HeapRegion* allocate_free_region(HeapRegionType type) {
178 HeapRegion* hr = _free_list.remove_region(!type.is_young());
179
180 if (hr != NULL) {
181 assert(hr->next() == NULL, "Single region should not have next");
182 assert(is_available(hr->hrm_index()), "Must be committed");
183 }
184 return hr;
185 }
186
187 inline void allocate_free_regions_starting_at(uint first, uint num_regions);
188
189 // Remove all regions from the free list.
190 void remove_all_free_regions() {
191 _free_list.remove_all();
192 }
193
194 // Return the number of committed free regions in the heap.
195 uint num_free_regions() const {
196 return _free_list.length();
197 }
198
199 size_t total_free_bytes() const {
200 return num_free_regions() * HeapRegion::GrainBytes;
201 }
202
203 // Return the number of available (uncommitted) regions.
204 uint available() const { return max_length() - length(); }
205
206 // Return the number of regions that have been committed in the heap.
207 uint length() const { return _num_committed; }
208
209 // Return the maximum number of regions in the heap.
210 uint max_length() const { return (uint)_regions.length(); }
211
212 // Return maximum number of regions that heap can expand to.
213 virtual uint max_expandable_length() const { return (uint)_regions.length(); }
214
215 MemoryUsage get_auxiliary_data_memory_usage() const;
216
217 MemRegion reserved() const { return MemRegion(heap_bottom(), heap_end()); }
218
219 // Expand the sequence to reflect that the heap has grown. Either create new
220 // HeapRegions, or re-use existing ones. Returns the number of regions the
221 // sequence was expanded by. If a HeapRegion allocation fails, the resulting
222 // number of regions might be smaller than what's desired.
223 virtual uint expand_by(uint num_regions, WorkGang* pretouch_workers);
224
225 // Makes sure that the regions from start to start+num_regions-1 are available
226 // for allocation. Returns the number of regions that were committed to achieve
227 // this.
228 virtual uint expand_at(uint start, uint num_regions, WorkGang* pretouch_workers);
229
230 // Find a contiguous set of empty regions of length num. Returns the start index of
231 // that set, or G1_NO_HRM_INDEX.
232 virtual uint find_contiguous_only_empty(size_t num) { return find_contiguous(num, true); }
233 // Find a contiguous set of empty or unavailable regions of length num. Returns the
234 // start index of that set, or G1_NO_HRM_INDEX.
235 virtual uint find_contiguous_empty_or_unavailable(size_t num) { return find_contiguous(num, false); }
236
237 HeapRegion* next_region_in_heap(const HeapRegion* r) const;
238
239 // Find the highest free or uncommitted region in the reserved heap,
240 // and if uncommitted, commit it. If none are available, return G1_NO_HRM_INDEX.
241 // Set the 'expanded' boolean true if a new region was committed.
242 virtual uint find_highest_free(bool* expanded);
243
244 // Allocate the regions that contain the address range specified, committing the
245 // regions if necessary. Return false if any of the regions is already committed
246 // and not free, and return the number of regions newly committed in commit_count.
247 bool allocate_containing_regions(MemRegion range, size_t* commit_count, WorkGang* pretouch_workers);
248
249 // Apply blk->do_heap_region() on all committed regions in address order,
250 // terminating the iteration early if do_heap_region() returns true.
251 void iterate(HeapRegionClosure* blk) const;
252
253 void par_iterate(HeapRegionClosure* blk, HeapRegionClaimer* hrclaimer, const uint start_index) const;
254
255 // Uncommit up to num_regions_to_remove regions that are completely free.
256 // Return the actual number of uncommitted regions.
257 virtual uint shrink_by(uint num_regions_to_remove);
258
259 // Uncommit a number of regions starting at the specified index, which must be available,
260 // empty, and free.
261 void shrink_at(uint index, size_t num_regions);
262
263 virtual void verify();
264
265 // Do some sanity checking.
266 void verify_optional() PRODUCT_RETURN;
267};
268
269// The HeapRegionClaimer is used during parallel iteration over heap regions,
270// allowing workers to claim heap regions, gaining exclusive rights to these regions.
271class HeapRegionClaimer : public StackObj {
272 uint _n_workers;
273 uint _n_regions;
274 volatile uint* _claims;
275
276 static const uint Unclaimed = 0;
277 static const uint Claimed = 1;
278
279 public:
280 HeapRegionClaimer(uint n_workers);
281 ~HeapRegionClaimer();
282
283 inline uint n_regions() const {
284 return _n_regions;
285 }
286
287 // Return a start offset given a worker id.
288 uint offset_for_worker(uint worker_id) const;
289
290 // Check if region has been claimed with this HRClaimer.
291 bool is_region_claimed(uint region_index) const;
292
293 // Claim the given region, returns true if successfully claimed.
294 bool claim_region(uint region_index);
295};
296#endif // SHARE_GC_G1_HEAPREGIONMANAGER_HPP
297