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/*
* Copyright (c) 2012, Oracle and/or its affiliates. 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
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/
#ifndef SHARE_VM_MEMORY_METACHUNK_HPP
#define SHARE_VM_MEMORY_METACHUNK_HPP
// Metachunk - Quantum of allocation from a Virtualspace
// Metachunks are reused (when freed are put on a global freelist) and
// have no permanent association to a SpaceManager.
// +--------------+ <- end
// | | --+ ---+
// | | | free |
// | | | |
// | | | | capacity
// | | | |
// | | <- top --+ |
// | | ---+ |
// | | | used |
// | | | |
// | | | |
// +--------------+ <- bottom ---+ ---+
class Metachunk VALUE_OBJ_CLASS_SPEC {
// link to support lists of chunks
Metachunk* _next;
Metachunk* _prev;
MetaWord* _bottom;
MetaWord* _end;
MetaWord* _top;
size_t _word_size;
// Used in a guarantee() so included in the Product builds
// even through it is only for debugging.
bool _is_free;
// Metachunks are allocated out of a MetadataVirtualSpace and
// and use some of its space to describe itself (plus alignment
// considerations). Metadata is allocated in the rest of the chunk.
// This size is the overhead of maintaining the Metachunk within
// the space.
static size_t _overhead;
void set_bottom(MetaWord* v) { _bottom = v; }
void set_end(MetaWord* v) { _end = v; }
void set_top(MetaWord* v) { _top = v; }
void set_word_size(size_t v) { _word_size = v; }
public:
#ifdef ASSERT
Metachunk() : _bottom(NULL), _end(NULL), _top(NULL), _is_free(false) {}
#else
Metachunk() : _bottom(NULL), _end(NULL), _top(NULL) {}
#endif
// Used to add a Metachunk to a list of Metachunks
void set_next(Metachunk* v) { _next = v; assert(v != this, "Boom");}
void set_prev(Metachunk* v) { _prev = v; assert(v != this, "Boom");}
MetaWord* allocate(size_t word_size);
static Metachunk* initialize(MetaWord* ptr, size_t word_size);
// Accessors
Metachunk* next() const { return _next; }
Metachunk* prev() const { return _prev; }
MetaWord* bottom() const { return _bottom; }
MetaWord* end() const { return _end; }
MetaWord* top() const { return _top; }
size_t word_size() const { return _word_size; }
size_t size() const volatile { return _word_size; }
void set_size(size_t v) { _word_size = v; }
bool is_free() { return _is_free; }
void set_is_free(bool v) { _is_free = v; }
static size_t overhead() { return _overhead; }
void clear_next() { set_next(NULL); }
void link_prev(Metachunk* ptr) { set_prev(ptr); }
uintptr_t* end() { return ((uintptr_t*) this) + size(); }
bool cantCoalesce() const { return false; }
void link_next(Metachunk* ptr) { set_next(ptr); }
void link_after(Metachunk* ptr){
link_next(ptr);
if (ptr != NULL) ptr->link_prev(this);
}
// Reset top to bottom so chunk can be reused.
void reset_empty() { _top = (_bottom + _overhead); }
bool is_empty() { return _top == (_bottom + _overhead); }
// used (has been allocated)
// free (available for future allocations)
// capacity (total size of chunk)
size_t used_word_size();
size_t free_word_size();
size_t capacity_word_size();
// Debug support
#ifdef ASSERT
void* prev_addr() const { return (void*)&_prev; }
void* next_addr() const { return (void*)&_next; }
void* size_addr() const { return (void*)&_word_size; }
#endif
bool verify_chunk_in_free_list(Metachunk* tc) const { return true; }
bool verify_par_locked() { return true; }
void assert_is_mangled() const {/* Don't check "\*/}
#ifdef ASSERT
void mangle();
#endif // ASSERT
void print_on(outputStream* st) const;
void verify();
};
#endif // SHARE_VM_MEMORY_METACHUNK_HPP
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