1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
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  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
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  24 
  25 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP
  26 #define SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP
  27 
  28 #include "gc_implementation/g1/g1BiasedArray.hpp"
  29 #include "gc_implementation/g1/g1RegionToSpaceMapper.hpp"
  30 #include "gc_implementation/g1/heapRegionSet.hpp"
  31 
  32 class HeapRegion;
  33 class HeapRegionClosure;
  34 class FreeRegionList;
  35 
  36 class G1HeapRegionTable : public G1BiasedMappedArray<HeapRegion*> {
  37  protected:
  38   virtual HeapRegion* default_value() const { return NULL; }
  39 };
  40 
  41 // This class keeps track of the actual heap memory, auxiliary data
  42 // and its metadata (i.e., HeapRegion instances) and the list of free regions.
  43 //
  44 // This allows maximum flexibility for deciding what to commit or uncommit given
  45 // a request from outside.
  46 //
  47 // HeapRegions are kept in the _regions array in address order. A region's
  48 // index in the array corresponds to its index in the heap (i.e., 0 is the
  49 // region at the bottom of the heap, 1 is the one after it, etc.). Two
  50 // regions that are consecutive in the array should also be adjacent in the
  51 // address space (i.e., region(i).end() == region(i+1).bottom().
  52 //
  53 // We create a HeapRegion when we commit the region's address space
  54 // for the first time. When we uncommit the address space of a
  55 // region we retain the HeapRegion to be able to re-use it in the
  56 // future (in case we recommit it).
  57 //
  58 // We keep track of three lengths:
  59 //
  60 // * _num_committed (returned by length()) is the number of currently
  61 //   committed regions. These may not be contiguous.
  62 // * _allocated_heapregions_length (not exposed outside this class) is the
  63 //   number of regions+1 for which we have HeapRegions.
  64 // * max_length() returns the maximum number of regions the heap can have.
  65 //
  66 
  67 class HeapRegionSeq: public CHeapObj<mtGC> {
  68   friend class VMStructs;
  69 
  70   G1HeapRegionTable _regions;
  71 
  72   G1RegionToSpaceMapper* _heap_mapper;
  73   G1RegionToSpaceMapper* _prev_bitmap_mapper;
  74   G1RegionToSpaceMapper* _next_bitmap_mapper;
  75   G1RegionToSpaceMapper* _bot_mapper;
  76   G1RegionToSpaceMapper* _cardtable_mapper;
  77   G1RegionToSpaceMapper* _card_counts_mapper;
  78 
  79   FreeRegionList _free_list;
  80 
  81   // Each bit in this bitmap indicates that the corresponding region is available
  82   // for allocation.
  83   BitMap _available_map;
  84 
  85    // The number of regions committed in the heap.
  86   uint _num_committed;
  87 
  88   // Internal only. The highest heap region +1 we allocated a HeapRegion instance for.
  89   uint _allocated_heapregions_length;
  90 
  91   HeapWord* heap_bottom() const { return _regions.bottom_address_mapped(); }
  92   HeapWord* heap_end() const {return _regions.end_address_mapped(); }
  93 
  94   void make_regions_available(uint index, uint num_regions = 1);
  95 
  96   // Pass down commit calls to the VirtualSpace.
  97   void commit_regions(uint index, size_t num_regions = 1);
  98   void uncommit_regions(uint index, size_t num_regions = 1);
  99 
 100   // Notify other data structures about change in the heap layout.
 101   void update_committed_space(HeapWord* old_end, HeapWord* new_end);
 102   // Calculate the starting region for each worker during parallel iteration so
 103   // that they do not all start from the same region.
 104   uint start_region_for_worker(uint worker_i, uint num_workers, uint num_regions) const;
 105 
 106   // Find a contiguous set of empty or uncommitted regions of length num and return
 107   // the index of the first region or G1_NO_HRS_INDEX if the search was unsuccessful.
 108   // If only_empty is true, only empty regions are considered.
 109   // Searches from bottom to top of the heap, doing a first-fit.
 110   uint find_contiguous(size_t num, bool only_empty);
 111   // Finds the next sequence of unavailable regions starting from start_idx. Returns the
 112   // length of the sequence found. If this result is zero, no such sequence could be found,
 113   // otherwise res_idx indicates the start index of these regions.
 114   uint find_unavailable_from_idx(uint start_idx, uint* res_idx) const;
 115   // Finds the next sequence of empty regions starting from start_idx, going backwards in
 116   // the heap. Returns the length of the sequence found. If this value is zero, no
 117   // sequence could be found, otherwise res_idx contains the start index of this range.
 118   uint find_empty_from_idx_reverse(uint start_idx, uint* res_idx) const;
 119   // Allocate a new HeapRegion for the given index.
 120   HeapRegion* new_heap_region(uint hrs_index);
 121 #ifdef ASSERT
 122 public:
 123   bool is_free(HeapRegion* hr) const;
 124 #endif
 125   // Returns whether the given region is available for allocation.
 126   bool is_available(uint region) const;
 127 
 128  public:
 129   // Empty constructor, we'll initialize it with the initialize() method.
 130   HeapRegionSeq() : _regions(), _heap_mapper(NULL), _num_committed(0),
 131                     _next_bitmap_mapper(NULL), _prev_bitmap_mapper(NULL), _bot_mapper(NULL),
 132                     _allocated_heapregions_length(0), _available_map(),
 133                     _free_list("Free list", new MasterFreeRegionListMtSafeChecker())
 134   { }
 135 
 136   void initialize(G1RegionToSpaceMapper* heap_storage,
 137                   G1RegionToSpaceMapper* prev_bitmap,
 138                   G1RegionToSpaceMapper* next_bitmap,
 139                   G1RegionToSpaceMapper* bot,
 140                   G1RegionToSpaceMapper* cardtable,
 141                   G1RegionToSpaceMapper* card_counts);
 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   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   // If addr is within the committed space return its corresponding
 154   // HeapRegion, otherwise return NULL.
 155   inline HeapRegion* addr_to_region(HeapWord* addr) const;
 156 
 157   // Insert the given region into the free region list.
 158   inline void insert_into_free_list(HeapRegion* hr);
 159 
 160   // Insert the given region list into the global free region list.
 161   void insert_list_into_free_list(FreeRegionList* list) {
 162     _free_list.add_ordered(list);
 163   }
 164 
 165   HeapRegion* allocate_free_region(bool is_old) {
 166     HeapRegion* hr = _free_list.remove_region(is_old);
 167 
 168     if (hr != NULL) {
 169       assert(hr->next() == NULL, "Single region should not have next");
 170       assert(is_available(hr->hrs_index()), "Must be committed");
 171     }
 172     return hr;
 173   }
 174 
 175   inline void allocate_free_regions_starting_at(uint first, uint num_regions);
 176 
 177   // Remove all regions from the free list.
 178   void remove_all_free_regions() {
 179     _free_list.remove_all();
 180   }
 181 
 182   // Return the number of committed free regions in the heap.
 183   uint num_free_regions() const {
 184     return _free_list.length();
 185   }
 186 
 187   size_t total_capacity_bytes() const {
 188     return num_free_regions() * HeapRegion::GrainBytes;
 189   }
 190 
 191   // Return the number of available (uncommitted) regions.
 192   uint available() const { return max_length() - length(); }
 193 
 194   // Return the number of regions that have been committed in the heap.
 195   uint length() const { return _num_committed; }
 196 
 197   // Return the maximum number of regions in the heap.
 198   uint max_length() const { return (uint)_regions.length(); }
 199 
 200   MemRegion reserved() const { return MemRegion(heap_bottom(), heap_end()); }
 201 
 202   // Expand the sequence to reflect that the heap has grown. Either create new
 203   // HeapRegions, or re-use existing ones. Returns the number of regions the
 204   // sequence was expanded by. If a HeapRegion allocation fails, the resulting
 205   // number of regions might be smaller than what's desired.
 206   uint expand_by(uint num_regions);
 207 
 208   // Makes sure that the regions from start to start+num_regions-1 are available
 209   // for allocation. Returns the number of regions that were committed to achieve
 210   // this.
 211   uint expand_at(uint start, uint num_regions);
 212 
 213   // Find a contiguous set of empty regions of length num. Returns the start index of
 214   // that set, or G1_NO_HRS_INDEX.
 215   uint find_contiguous_only_empty(size_t num) { return find_contiguous(num, true); }
 216   // Find a contiguous set of empty or unavailable regions of length num. Returns the
 217   // start index of that set, or G1_NO_HRS_INDEX.
 218   uint find_contiguous_empty_or_unavailable(size_t num) { return find_contiguous(num, false); }
 219 
 220   HeapRegion* next_region_in_heap(const HeapRegion* r) const;
 221 
 222   // Apply blk->doHeapRegion() on all committed regions in address order,
 223   // terminating the iteration early if doHeapRegion() returns true.
 224   void iterate(HeapRegionClosure* blk) const;
 225   void iterate_range(HeapRegionClosure* blk, uint start, uint end) const;
 226 
 227   void par_iterate(HeapRegionClosure* blk, uint worker_id, uint no_of_par_workers, jint claim_value) const;
 228 
 229   // Uncommit up to num_regions_to_remove regions that are completely free.
 230   // Return the actual number of uncommitted regions.
 231   uint shrink_by(uint num_regions_to_remove);
 232 
 233   void verify();
 234 
 235   // Do some sanity checking.
 236   void verify_optional() PRODUCT_RETURN;
 237 };
 238 
 239 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_HEAPREGIONSEQ_HPP
 240