1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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24
25 #ifndef SHARE_VM_GC_G1_HEAPREGIONMANAGER_HPP
26 #define SHARE_VM_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
33 class HeapRegion;
34 class HeapRegionClosure;
35 class HeapRegionClaimer;
36 class FreeRegionList;
37 class WorkGang;
38
39 class 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
70 class HeapRegionManager: public CHeapObj<mtGC> {
71 friend class VMStructs;
72 friend class HeapRegionClaimer;
73
74 G1RegionToSpaceMapper* _prev_bitmap_mapper;
75 G1RegionToSpaceMapper* _next_bitmap_mapper;
76 G1RegionToSpaceMapper* _bot_mapper;
77 G1RegionToSpaceMapper* _cardtable_mapper;
78 G1RegionToSpaceMapper* _card_counts_mapper;
79
80 // Each bit in this bitmap indicates that the corresponding region is available
81 // for allocation.
82 CHeapBitMap _available_map;
83
84 // The number of regions committed in the heap.
85 uint _num_committed;
86
87 // Internal only. The highest heap region +1 we allocated a HeapRegion instance for.
88 uint _allocated_heapregions_length;
89
90 HeapWord* heap_bottom() const { return _regions.bottom_address_mapped(); }
91 HeapWord* heap_end() const {return _regions.end_address_mapped(); }
92
93 // Pass down commit calls to the VirtualSpace.
94 void commit_regions(uint index, size_t num_regions = 1, WorkGang* pretouch_gang = NULL);
95
96 // Notify other data structures about change in the heap layout.
97 void update_committed_space(HeapWord* old_end, HeapWord* new_end);
98
99 // Find a contiguous set of empty or uncommitted regions of length num and return
100 // the index of the first region or G1_NO_HRM_INDEX if the search was unsuccessful.
101 // If only_empty is true, only empty regions are considered.
102 // Searches from bottom to top of the heap, doing a first-fit.
103 uint find_contiguous(size_t num, bool only_empty);
104 // Finds the next sequence of unavailable regions starting from start_idx. Returns the
105 // length of the sequence found. If this result is zero, no such sequence could be found,
106 // otherwise res_idx indicates the start index of these regions.
107 uint find_unavailable_from_idx(uint start_idx, uint* res_idx) const;
108 // Finds the next sequence of empty regions starting from start_idx, going backwards in
109 // the heap. Returns the length of the sequence found. If this value is zero, no
110 // sequence could be found, otherwise res_idx contains the start index of this range.
111 uint find_empty_from_idx_reverse(uint start_idx, uint* res_idx) const;
112
113 protected:
114 G1HeapRegionTable _regions;
115 G1RegionToSpaceMapper* _heap_mapper;
116 FreeRegionList _free_list;
117 void make_regions_available(uint index, uint num_regions = 1, WorkGang* pretouch_gang = NULL);
118 void uncommit_regions(uint index, size_t num_regions = 1);
119 // Allocate a new HeapRegion for the given index.
120 HeapRegion* new_heap_region(uint hrm_index);
121 #ifdef ASSERT
122 public:
123 bool is_free(HeapRegion* hr) const;
124 #endif
125 public:
126 // Empty constructor, we'll initialize it with the initialize() method.
127 HeapRegionManager();
128
129 static HeapRegionManager* create_manager(G1CollectedHeap* heap, CollectorPolicy* policy);
130
131 void initialize(G1RegionToSpaceMapper* heap_storage,
132 G1RegionToSpaceMapper* prev_bitmap,
133 G1RegionToSpaceMapper* next_bitmap,
134 G1RegionToSpaceMapper* bot,
135 G1RegionToSpaceMapper* cardtable,
136 G1RegionToSpaceMapper* card_counts);
137
138 // Prepare heap regions before and after full collection.
139 // Nothing to be done in this class.
140 virtual void prepare_for_full_collection_start() {}
141 virtual void prepare_for_full_collection_end() {}
142
143 // Return the "dummy" region used for G1AllocRegion. This is currently a hardwired
144 // new HeapRegion that owns HeapRegion at index 0. Since at the moment we commit
145 // the heap from the lowest address, this region (and its associated data
146 // structures) are available and we do not need to check further.
147 virtual HeapRegion* get_dummy_region() { return new_heap_region(0); }
148
149 // Return the HeapRegion at the given index. Assume that the index
150 // is valid.
151 inline HeapRegion* at(uint index) const;
152
153 // Return the HeapRegion at the given index, NULL if the index
154 // is for an unavailable region.
155 inline HeapRegion* at_or_null(uint index) const;
156
157 // Returns whether the given region is available for allocation.
158 bool is_available(uint region) const;
159
160 // Return the next region (by index) that is part of the same
161 // humongous object that hr is part of.
162 inline HeapRegion* next_region_in_humongous(HeapRegion* hr) const;
163
164 // If addr is within the committed space return its corresponding
165 // HeapRegion, otherwise return NULL.
166 inline HeapRegion* addr_to_region(HeapWord* addr) const;
167
168 // Insert the given region into the free region list.
169 inline void insert_into_free_list(HeapRegion* hr);
170
171 // Insert the given region list into the global free region list.
172 void insert_list_into_free_list(FreeRegionList* list) {
173 _free_list.add_ordered(list);
174 }
175
176 virtual HeapRegion* allocate_free_region(bool is_old) {
177 HeapRegion* hr = _free_list.remove_region(is_old);
178
179 if (hr != NULL) {
180 assert(hr->next() == NULL, "Single region should not have next");
181 assert(is_available(hr->hrm_index()), "Must be committed");
182 }
183 return hr;
184 }
185
186 inline void allocate_free_regions_starting_at(uint first, uint num_regions);
187
188 // Remove all regions from the free list.
189 void remove_all_free_regions() {
190 _free_list.remove_all();
191 }
192
193 // Return the number of committed free regions in the heap.
194 uint num_free_regions() const {
195 return _free_list.length();
196 }
197
198 size_t total_free_bytes() const {
199 return num_free_regions() * HeapRegion::GrainBytes;
200 }
201
202 // Return the number of available (uncommitted) regions.
203 uint available() const { return max_length() - length(); }
204
205 // Return the number of regions that have been committed in the heap.
206 uint length() const { return _num_committed; }
207
208 // Return the maximum number of regions in the heap.
209 uint max_length() const { return (uint)_regions.length(); }
210
211 // Return maximum number of regions that heap can expand to.
212 virtual uint max_expandable_length() const { return (uint)_regions.length(); }
213
214 MemoryUsage get_auxiliary_data_memory_usage() const;
215
216 MemRegion reserved() const { return MemRegion(heap_bottom(), heap_end()); }
217
218 // Expand the sequence to reflect that the heap has grown. Either create new
219 // HeapRegions, or re-use existing ones. Returns the number of regions the
220 // sequence was expanded by. If a HeapRegion allocation fails, the resulting
221 // number of regions might be smaller than what's desired.
222 virtual uint expand_by(uint num_regions, WorkGang* pretouch_workers);
223
224 // Makes sure that the regions from start to start+num_regions-1 are available
225 // for allocation. Returns the number of regions that were committed to achieve
226 // this.
227 virtual uint expand_at(uint start, uint num_regions, WorkGang* pretouch_workers);
228
229 // Find a contiguous set of empty regions of length num. Returns the start index of
230 // that set, or G1_NO_HRM_INDEX.
231 virtual uint find_contiguous_only_empty(size_t num) { return find_contiguous(num, true); }
232 // Find a contiguous set of empty or unavailable regions of length num. Returns the
233 // start index of that set, or G1_NO_HRM_INDEX.
234 virtual uint find_contiguous_empty_or_unavailable(size_t num) { return find_contiguous(num, false); }
235
236 HeapRegion* next_region_in_heap(const HeapRegion* r) const;
237
238 // Find the highest free or uncommitted region in the reserved heap,
239 // and if uncommitted, commit it. If none are available, return G1_NO_HRM_INDEX.
240 // Set the 'expanded' boolean true if a new region was committed.
241 virtual uint find_highest_free(bool* expanded);
242
243 // Allocate the regions that contain the address range specified, committing the
244 // regions if necessary. Return false if any of the regions is already committed
245 // and not free, and return the number of regions newly committed in commit_count.
246 bool allocate_containing_regions(MemRegion range, size_t* commit_count, WorkGang* pretouch_workers);
247
248 // Apply blk->do_heap_region() on all committed regions in address order,
249 // terminating the iteration early if do_heap_region() returns true.
250 void iterate(HeapRegionClosure* blk) const;
251
252 void par_iterate(HeapRegionClosure* blk, HeapRegionClaimer* hrclaimer, const uint start_index) const;
253
254 // Uncommit up to num_regions_to_remove regions that are completely free.
255 // Return the actual number of uncommitted regions.
256 virtual uint shrink_by(uint num_regions_to_remove);
257
258 // Uncommit a number of regions starting at the specified index, which must be available,
259 // empty, and free.
260 void shrink_at(uint index, size_t num_regions);
261
262 virtual void verify();
263
264 // Do some sanity checking.
265 void verify_optional() PRODUCT_RETURN;
266 };
267
268 // The HeapRegionClaimer is used during parallel iteration over heap regions,
269 // allowing workers to claim heap regions, gaining exclusive rights to these regions.
270 class HeapRegionClaimer : public StackObj {
271 uint _n_workers;
272 uint _n_regions;
273 volatile uint* _claims;
274
275 static const uint Unclaimed = 0;
276 static const uint Claimed = 1;
277
278 public:
279 HeapRegionClaimer(uint n_workers);
280 ~HeapRegionClaimer();
281
282 inline uint n_regions() const {
283 return _n_regions;
284 }
285
286 // Return a start offset given a worker id.
287 uint offset_for_worker(uint worker_id) const;
288
289 // Check if region has been claimed with this HRClaimer.
290 bool is_region_claimed(uint region_index) const;
291
292 // Claim the given region, returns true if successfully claimed.
293 bool claim_region(uint region_index);
294 };
295 #endif // SHARE_VM_GC_G1_HEAPREGIONMANAGER_HPP