/*
 * Copyright (c) 2018, 2019, Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 2018, 2019 SAP SE. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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#ifndef SHARE_MEMORY_METASPACE_VIRTUALSPACENODE_HPP
#define SHARE_MEMORY_METASPACE_VIRTUALSPACENODE_HPP


#include <memory/metaspace/settings.hpp>
#include "memory/allocation.hpp"
#include "memory/metaspace/counter.hpp"
#include "memory/metaspace/commitMask.hpp"
#include "memory/metaspace/rootChunkArea.hpp"
#include "memory/virtualspace.hpp"
#include "memory/memRegion.hpp"
#include "utilities/debug.hpp"
#include "utilities/bitMap.hpp"
#include "utilities/globalDefinitions.hpp"


class outputStream;

namespace metaspace {

class CommitLimiter;
class MetachunkListCluster;

// VirtualSpaceNode manages a single address range of the Metaspace.
//
// That address range may contain interleaved committed and uncommitted
// regions. It keeps track of which regions have committed and offers
// functions to commit and uncommit regions.
//
// It allocates and hands out memory ranges, starting at the bottom.
//
// Address range must be aligned to root chunk size.
//
class VirtualSpaceNode : public CHeapObj<mtClass> {

  // Link to next VirtualSpaceNode
  VirtualSpaceNode* _next;

  ReservedSpace _rs;

  // Start pointer of the area.
  MetaWord* const _base;

  // Size, in words, of the whole node
  const size_t _word_size;

  // Size, in words, of the range of this node which has been handed out in
  // the form of chunks.
  size_t _used_words;

  // The bitmap describing the commit state of the region:
  // Each bit covers a region of 64K (see constants::commit_granule_size).
  CommitMask _commit_mask;

  // An array/LUT of RootChunkArea objects. Each one describes
  // fragmentation inside a root chunk.
  RootChunkAreaLUT _root_chunk_area_lut;

  // Limiter object to ask before expanding the committed size of this node.
  CommitLimiter* const _commit_limiter;

  // Points to outside size counters which we are to increase/decrease when we commit/uncommit
  // space from this node.
  SizeCounter* const _total_reserved_words_counter;
  SizeCounter* const _total_committed_words_counter;

  // For debug and tracing purposes
  const int _node_id;

  /// committing, uncommitting ///

  // Given a pointer into this node, calculate the start of the commit granule
  // the pointer points into.
  MetaWord* calc_start_of_granule(MetaWord* p) const {
    DEBUG_ONLY(check_pointer(p));
    return align_down(p, Settings::commit_granule_bytes());
  }

  // Given an address range, ensure it is committed.
  //
  // The range has to be aligned to granule size.
  //
  // Function will:
  // - check how many granules in that region are uncommitted; If all are committed, it
  //    returns true immediately.
  // - check if committing those uncommitted granules would bring us over the commit limit
  //    (GC threshold, MaxMetaspaceSize). If true, it returns false.
  // - commit the memory.
  // - mark the range as committed in the commit mask
  //
  // Returns true if success, false if it did hit a commit limit.
  bool commit_range(MetaWord* p, size_t word_size);

  //// creation ////

  // Create a new empty node spanning the given reserved space.
  VirtualSpaceNode(int node_id,
                   ReservedSpace rs,
                   CommitLimiter* limiter,
                   SizeCounter* reserve_counter,
                   SizeCounter* commit_counter);

  MetaWord* base() const        { return _base; }

public:

  // Create a node of a given size
  static VirtualSpaceNode* create_node(int node_id,
                                       size_t word_size,
                                       CommitLimiter* limiter,
                                       SizeCounter* reserve_words_counter,
                                       SizeCounter* commit_words_counter);

  // Create a node over an existing space
  static VirtualSpaceNode* create_node(int node_id,
                                       ReservedSpace rs,
                                       CommitLimiter* limiter,
                                       SizeCounter* reserve_words_counter,
                                       SizeCounter* commit_words_counter);

  ~VirtualSpaceNode();


  // Reserved size of the whole node.
  size_t word_size() const      { return _word_size; }

  //// Chunk allocation, splitting, merging /////

  // Allocate a root chunk from this node. Will fail and return NULL
  // if the node is full.
  // Note: this just returns a chunk whose memory is reserved; no memory is committed yet.
  // Hence, before using this chunk, it must be committed.
  // Also, no limits are checked, since no committing takes place.
  Metachunk* allocate_root_chunk();

  // Given a chunk c, split it recursively until you get a chunk of the given target_level.
  //
  // The original chunk must not be part of a freelist.
  //
  // Returns pointer to the result chunk; the splitted-off chunks are added as
  //  free chunks to the freelists.
  //
  // Returns NULL if chunk cannot be split at least once.
  Metachunk* split(chklvl_t target_level, Metachunk* c, MetachunkListCluster* freelists);

  // Given a chunk, attempt to merge it recursively with its neighboring chunks.
  //
  // If successful (merged at least once), returns address of
  // the merged chunk; NULL otherwise.
  //
  // The merged chunks are removed from the freelists.
  //
  // !!! Please note that if this method returns a non-NULL value, the
  // original chunk will be invalid and should not be accessed anymore! !!!
  Metachunk* merge(Metachunk* c, MetachunkListCluster* freelists);

  // Given a chunk c, which must be "in use" and must not be a root chunk, attempt to
  // enlarge it in place by claiming its trailing buddy.
  //
  // This will only work if c is the leader of the buddy pair and the trailing buddy is free.
  //
  // If successful, the follower chunk will be removed from the freelists, the leader chunk c will
  // double in size (level decreased by one).
  //
  // On success, true is returned, false otherwise.
  bool attempt_enlarge_chunk(Metachunk* c, MetachunkListCluster* freelists);

  // Attempts to purge the node:
  //
  // If all chunks living in this node are free, they will all be removed from their freelists
  //   and deletes the node.
  //
  // Returns true if the node has been deleted, false if not.
  // !! If this returns true, do not access the node from this point on. !!
  bool attempt_purge(MetachunkListCluster* freelists);

  // Attempts to uncommit free areas according to the rules set in settings.
  // Returns number of words uncommitted.
  size_t uncommit_free_areas();

  /// misc /////

  // Returns size, in words, of the used space in this node alone.
  // (Notes:
  //  - This is the space handed out to the ChunkManager, so it is "used" from the viewpoint of this node,
  //    but not necessarily used for Metadata.
  //  - This may or may not be committed memory.
  size_t used_words() const             { return _used_words; }

  // Returns size, in words, of how much space is left in this node alone.
  size_t free_words() const             { return _word_size - _used_words; }

  // Returns size, in words, of committed space in this node alone.
  // Note: iterates over commit mask and hence may be a tad expensive on large nodes.
  size_t committed_words() const;

  //// Committing/uncommitting memory /////

  // Given an address range, ensure it is committed.
  //
  // The range does not have to be aligned to granule size. However, the function will always commit
  // whole granules.
  //
  // Function will:
  // - check how many granules in that region are uncommitted; If all are committed, it
  //    returns true immediately.
  // - check if committing those uncommitted granules would bring us over the commit limit
  //    (GC threshold, MaxMetaspaceSize). If true, it returns false.
  // - commit the memory.
  // - mark the range as committed in the commit mask
  //
  // Returns true if success, false if it did hit a commit limit.
  bool ensure_range_is_committed(MetaWord* p, size_t word_size);

  // Given an address range (which has to be aligned to commit granule size):
  //  - uncommit it
  //  - mark it as uncommitted in the commit mask
  void uncommit_range(MetaWord* p, size_t word_size);

  //// List stuff ////
  VirtualSpaceNode* next() const        { return _next; }
  void set_next(VirtualSpaceNode* vsn)  { _next = vsn; }


  /// Debug stuff ////

  // Print a description about this node.
  void print_on(outputStream* st) const;

  // Verify counters and basic structure. Slow mode: verify all chunks in depth
  bool contains(const MetaWord* p) const {
    return p >= _base && p < _base + _used_words;
  }

#ifdef ASSERT
  void check_pointer(const MetaWord* p) const {
    assert(contains(p), "invalid pointer");
  }
  void verify(bool slow) const;
#endif

};


} // namespace metaspace

#endif // SHARE_MEMORY_METASPACE_VIRTUALSPACENODE_HPP