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
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  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_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   G1HeapRegionTable _regions;
  75 
  76   G1RegionToSpaceMapper* _heap_mapper;
  77   G1RegionToSpaceMapper* _prev_bitmap_mapper;
  78   G1RegionToSpaceMapper* _next_bitmap_mapper;
  79   G1RegionToSpaceMapper* _bot_mapper;
  80   G1RegionToSpaceMapper* _cardtable_mapper;
  81   G1RegionToSpaceMapper* _card_counts_mapper;
  82 
  83   FreeRegionList _free_list;
  84 
  85   // Each bit in this bitmap indicates that the corresponding region is available
  86   // for allocation.
  87   CHeapBitMap _available_map;
  88 
  89    // The number of regions committed in the heap.
  90   uint _num_committed;
  91 
  92   // Internal only. The highest heap region +1 we allocated a HeapRegion instance for.
  93   uint _allocated_heapregions_length;
  94 
  95   HeapWord* heap_bottom() const { return _regions.bottom_address_mapped(); }
  96   HeapWord* heap_end() const {return _regions.end_address_mapped(); }
  97 
  98   void make_regions_available(uint index, uint num_regions = 1, WorkGang* pretouch_gang = NULL);
  99 
 100   // Pass down commit calls to the VirtualSpace.
 101   void commit_regions(uint index, size_t num_regions = 1, WorkGang* pretouch_gang = NULL);
 102   void uncommit_regions(uint index, size_t num_regions = 1);
 103 
 104   // Notify other data structures about change in the heap layout.
 105   void update_committed_space(HeapWord* old_end, HeapWord* new_end);
 106 
 107   // Find a contiguous set of empty or uncommitted regions of length num and return
 108   // the index of the first region or G1_NO_HRM_INDEX if the search was unsuccessful.
 109   // If only_empty is true, only empty regions are considered.
 110   // Searches from bottom to top of the heap, doing a first-fit.
 111   uint find_contiguous(size_t num, bool only_empty);
 112   // Finds the next sequence of unavailable regions starting from start_idx. Returns the
 113   // length of the sequence found. If this result is zero, no such sequence could be found,
 114   // otherwise res_idx indicates the start index of these regions.
 115   uint find_unavailable_from_idx(uint start_idx, uint* res_idx) const;
 116   // Finds the next sequence of empty regions starting from start_idx, going backwards in
 117   // the heap. Returns the length of the sequence found. If this value is zero, no
 118   // sequence could be found, otherwise res_idx contains the start index of this range.
 119   uint find_empty_from_idx_reverse(uint start_idx, uint* res_idx) const;
 120   // Allocate a new HeapRegion for the given index.
 121   HeapRegion* new_heap_region(uint hrm_index);
 122 #ifdef ASSERT
 123 public:
 124   bool is_free(HeapRegion* hr) const;
 125 #endif
 126   // Returns whether the given region is available for allocation.
 127   bool is_available(uint region) const;
 128 
 129  public:
 130   // Empty constructor, we'll initialize it with the initialize() method.
 131   HeapRegionManager() : _regions(), _heap_mapper(NULL), _num_committed(0),
 132                     _next_bitmap_mapper(NULL), _prev_bitmap_mapper(NULL), _bot_mapper(NULL),
 133                     _allocated_heapregions_length(0), _available_map(),
 134                     _free_list("Free list", new MasterFreeRegionListMtSafeChecker())
 135   { }
 136 
 137   void initialize(G1RegionToSpaceMapper* heap_storage,
 138                   G1RegionToSpaceMapper* prev_bitmap,
 139                   G1RegionToSpaceMapper* next_bitmap,
 140                   G1RegionToSpaceMapper* bot,
 141                   G1RegionToSpaceMapper* cardtable,
 142                   G1RegionToSpaceMapper* card_counts);
 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   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 next region (by index) that is part of the same
 155   // humongous object that hr is part of.
 156   inline HeapRegion* next_region_in_humongous(HeapRegion* hr) const;
 157 
 158   // If addr is within the committed space return its corresponding
 159   // HeapRegion, otherwise return NULL.
 160   inline HeapRegion* addr_to_region(HeapWord* addr) const;
 161 
 162   // Insert the given region into the free region list.
 163   inline void insert_into_free_list(HeapRegion* hr);
 164 
 165   // Insert the given region list into the global free region list.
 166   void insert_list_into_free_list(FreeRegionList* list) {
 167     _free_list.add_ordered(list);
 168   }
 169 
 170   HeapRegion* allocate_free_region(bool is_old) {
 171     HeapRegion* hr = _free_list.remove_region(is_old);
 172 
 173     if (hr != NULL) {
 174       assert(hr->next() == NULL, "Single region should not have next");
 175       assert(is_available(hr->hrm_index()), "Must be committed");
 176     }
 177     return hr;
 178   }
 179 
 180   inline void allocate_free_regions_starting_at(uint first, uint num_regions);
 181 
 182   // Remove all regions from the free list.
 183   void remove_all_free_regions() {
 184     _free_list.remove_all();
 185   }
 186 
 187   // Return the number of committed free regions in the heap.
 188   uint num_free_regions() const {
 189     return _free_list.length();
 190   }
 191 
 192   size_t total_capacity_bytes() const {
 193     return num_free_regions() * HeapRegion::GrainBytes;
 194   }
 195 
 196   // Return the number of available (uncommitted) regions.
 197   uint available() const { return max_length() - length(); }
 198 
 199   // Return the number of regions that have been committed in the heap.
 200   uint length() const { return _num_committed; }
 201 
 202   // Return the maximum number of regions in the heap.
 203   uint max_length() const { return (uint)_regions.length(); }
 204 
 205   MemoryUsage get_auxiliary_data_memory_usage() const;
 206 
 207   MemRegion reserved() const { return MemRegion(heap_bottom(), heap_end()); }
 208 
 209   // Expand the sequence to reflect that the heap has grown. Either create new
 210   // HeapRegions, or re-use existing ones. Returns the number of regions the
 211   // sequence was expanded by. If a HeapRegion allocation fails, the resulting
 212   // number of regions might be smaller than what's desired.
 213   uint expand_by(uint num_regions, WorkGang* pretouch_workers);
 214 
 215   // Makes sure that the regions from start to start+num_regions-1 are available
 216   // for allocation. Returns the number of regions that were committed to achieve
 217   // this.
 218   uint expand_at(uint start, uint num_regions, WorkGang* pretouch_workers);
 219 
 220   // Find a contiguous set of empty regions of length num. Returns the start index of
 221   // that set, or G1_NO_HRM_INDEX.
 222   uint find_contiguous_only_empty(size_t num) { return find_contiguous(num, true); }
 223   // Find a contiguous set of empty or unavailable regions of length num. Returns the
 224   // start index of that set, or G1_NO_HRM_INDEX.
 225   uint find_contiguous_empty_or_unavailable(size_t num) { return find_contiguous(num, false); }
 226 
 227   HeapRegion* next_region_in_heap(const HeapRegion* r) const;
 228 
 229   // Find the highest free or uncommitted region in the reserved heap,
 230   // and if uncommitted, commit it. If none are available, return G1_NO_HRM_INDEX.
 231   // Set the 'expanded' boolean true if a new region was committed.
 232   uint find_highest_free(bool* expanded);
 233 
 234   // Allocate the regions that contain the address range specified, committing the
 235   // regions if necessary. Return false if any of the regions is already committed
 236   // and not free, and return the number of regions newly committed in commit_count.
 237   bool allocate_containing_regions(MemRegion range, size_t* commit_count, WorkGang* pretouch_workers);
 238 
 239   // Apply blk->doHeapRegion() on all committed regions in address order,
 240   // terminating the iteration early if doHeapRegion() returns true.
 241   void iterate(HeapRegionClosure* blk) const;
 242 
 243   void par_iterate(HeapRegionClosure* blk, uint worker_id, HeapRegionClaimer* hrclaimer, bool concurrent) const;
 244 
 245   // Uncommit up to num_regions_to_remove regions that are completely free.
 246   // Return the actual number of uncommitted regions.
 247   uint shrink_by(uint num_regions_to_remove);
 248 
 249   // Uncommit a number of regions starting at the specified index, which must be available,
 250   // empty, and free.
 251   void shrink_at(uint index, size_t num_regions);
 252 
 253   void verify();
 254 
 255   // Do some sanity checking.
 256   void verify_optional() PRODUCT_RETURN;
 257 };
 258 
 259 // The HeapRegionClaimer is used during parallel iteration over heap regions,
 260 // allowing workers to claim heap regions, gaining exclusive rights to these regions.
 261 class HeapRegionClaimer : public StackObj {
 262   uint           _n_workers;
 263   uint           _n_regions;
 264   volatile uint* _claims;
 265 
 266   static const uint Unclaimed = 0;
 267   static const uint Claimed   = 1;
 268 
 269  public:
 270   HeapRegionClaimer(uint n_workers);
 271   ~HeapRegionClaimer();
 272 
 273   inline uint n_regions() const {
 274     return _n_regions;
 275   }
 276 
 277   // Calculate the starting region for given worker so
 278   // that they do not all start from the same region.
 279   uint start_region_for_worker(uint worker_id) const;
 280 
 281   // Check if region has been claimed with this HRClaimer.
 282   bool is_region_claimed(uint region_index) const;
 283 
 284   // Claim the given region, returns true if successfully claimed.
 285   bool claim_region(uint region_index);
 286 };
 287 #endif // SHARE_VM_GC_G1_HEAPREGIONMANAGER_HPP