src/hotspot/share/memory/metaspace/chunkHeaderPool.cpp

/*
 * Copyright (c) 2020, 2025, Oracle and/or its affiliates. All rights reserved.
 * Copyright (c) 2020 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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#include "memory/metaspace/chunkHeaderPool.hpp"
#include "runtime/os.hpp"
#include "utilities/debug.hpp"
#include "utilities/globalDefinitions.hpp"

namespace metaspace {

// Returns reference to the one global chunk header pool.
ChunkHeaderPool* ChunkHeaderPool::_chunkHeaderPool = nullptr;

ChunkHeaderPool::ChunkHeaderPool() :
  _num_slabs(),
  _first_slab(nullptr),
  _current_slab(nullptr)
{}

// Note: the global chunk header pool gets never deleted; so this destructor only
// exists for the sake of tests.
ChunkHeaderPool::~ChunkHeaderPool() {
  Slab* s = _first_slab;
  while (s != nullptr) {
    Slab* next_slab = s->_next;
    os::free(s);
     s = next_slab;
  }
}

void ChunkHeaderPool::allocate_new_slab() {
  Slab* slab = new Slab();
  if (_current_slab != nullptr) {
    _current_slab->_next = slab;
  }
  _current_slab = slab;
  if (_first_slab == nullptr) {
    _first_slab = slab;
  }
  _num_slabs.increment();
}

// Returns size of memory used.
size_t ChunkHeaderPool::memory_footprint_words() const {
  return (_num_slabs.get() * sizeof(Slab)) / BytesPerWord;
}

void ChunkHeaderPool::initialize() {
  assert(_chunkHeaderPool == nullptr, "only once");
  _chunkHeaderPool = new ChunkHeaderPool();
}

#ifdef ASSERT
void ChunkHeaderPool::verify() const {
  const Slab* s = _first_slab;
  int num = 0;
  while (s != nullptr) {
    assert(s->_top >= 0 && s->_top <= SlabCapacity,
           "invalid slab at " PTR_FORMAT ", top: %d, slab cap: %d",
           p2i(s), s->_top, SlabCapacity );
    s = s->_next;
    num++;
  }
  _num_slabs.check(num);
}
#endif

} // namespace metaspace