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/*
* Copyright (c) 2001, 2022, 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_GC_SHARED_PTRQUEUE_HPP
#define SHARE_GC_SHARED_PTRQUEUE_HPP
#include "gc/shared/freeListAllocator.hpp"
#include "memory/padded.hpp"
#include "utilities/align.hpp"
#include "utilities/debug.hpp"
#include "utilities/globalDefinitions.hpp"
#include "utilities/lockFreeStack.hpp"
#include "utilities/sizes.hpp"
// There are various techniques that require threads to be able to log
// addresses. For example, a generational write barrier might log
// the addresses of modified old-generation objects. This type supports
// this operation.
class BufferNode;
class PtrQueueSet;
class PtrQueue {
friend class VMStructs;
NONCOPYABLE(PtrQueue);
// The (byte) index at which an object was last enqueued. Starts at
// capacity (in bytes) (indicating an empty buffer) and goes towards zero.
// Value is always pointer-size aligned.
size_t _index;
// Size of the current buffer, in bytes.
// Value is always pointer-size aligned.
size_t _capacity_in_bytes;
static const size_t _element_size = sizeof(void*);
// Get the capacity, in bytes. The capacity must have been set.
size_t capacity_in_bytes() const {
assert(_capacity_in_bytes > 0, "capacity not set");
return _capacity_in_bytes;
}
static size_t byte_index_to_index(size_t ind) {
assert(is_aligned(ind, _element_size), "precondition");
return ind / _element_size;
}
static size_t index_to_byte_index(size_t ind) {
return ind * _element_size;
}
protected:
// The buffer.
void** _buf;
// Initialize this queue to contain a null buffer, and be part of the
// given PtrQueueSet.
PtrQueue(PtrQueueSet* qset);
// Requires queue flushed.
~PtrQueue();
public:
void** buffer() const { return _buf; }
void set_buffer(void** buffer) { _buf = buffer; }
size_t index() const {
return byte_index_to_index(_index);
}
void set_index(size_t new_index) {
assert(new_index <= capacity(), "precondition");
_index = index_to_byte_index(new_index);
}
size_t capacity() const {
return byte_index_to_index(capacity_in_bytes());
}
// To support compiler.
protected:
template<typename Derived>
static ByteSize byte_offset_of_index() {
return byte_offset_of(Derived, _index);
}
static constexpr ByteSize byte_width_of_index() { return in_ByteSize(sizeof(size_t)); }
template<typename Derived>
static ByteSize byte_offset_of_buf() {
return byte_offset_of(Derived, _buf);
}
static ByteSize byte_width_of_buf() { return in_ByteSize(_element_size); }
};
class BufferNode {
size_t _index;
BufferNode* volatile _next;
void* _buffer[1]; // Pseudo flexible array member.
BufferNode() : _index(0), _next(NULL) { }
~BufferNode() { }
NONCOPYABLE(BufferNode);
static size_t buffer_offset() {
return offset_of(BufferNode, _buffer);
}
public:
static BufferNode* volatile* next_ptr(BufferNode& bn) { return &bn._next; }
typedef LockFreeStack<BufferNode, &next_ptr> Stack;
BufferNode* next() const { return _next; }
void set_next(BufferNode* n) { _next = n; }
size_t index() const { return _index; }
void set_index(size_t i) { _index = i; }
// Return the BufferNode containing the buffer, after setting its index.
static BufferNode* make_node_from_buffer(void** buffer, size_t index) {
BufferNode* node =
reinterpret_cast<BufferNode*>(
reinterpret_cast<char*>(buffer) - buffer_offset());
node->set_index(index);
return node;
}
// Return the buffer for node.
static void** make_buffer_from_node(BufferNode *node) {
// &_buffer[0] might lead to index out of bounds warnings.
return reinterpret_cast<void**>(
reinterpret_cast<char*>(node) + buffer_offset());
}
class AllocatorConfig;
class Allocator; // Free-list based allocator.
class TestSupport; // Unit test support.
};
// We use BufferNode::AllocatorConfig to set the allocation options for the
// FreeListAllocator.
class BufferNode::AllocatorConfig : public FreeListConfig {
const size_t _buffer_size;
public:
explicit AllocatorConfig(size_t size);
~AllocatorConfig() = default;
void* allocate() override;
void deallocate(void* node) override;
size_t buffer_size() const { return _buffer_size; }
};
class BufferNode::Allocator {
friend class TestSupport;
AllocatorConfig _config;
FreeListAllocator _free_list;
NONCOPYABLE(Allocator);
public:
Allocator(const char* name, size_t buffer_size);
~Allocator() = default;
size_t buffer_size() const { return _config.buffer_size(); }
size_t free_count() const;
BufferNode* allocate();
void release(BufferNode* node);
};
// A PtrQueueSet represents resources common to a set of pointer queues.
// In particular, the individual queues allocate buffers from this shared
// set, and return completed buffers to the set.
class PtrQueueSet {
BufferNode::Allocator* _allocator;
NONCOPYABLE(PtrQueueSet);
protected:
// Create an empty ptr queue set.
PtrQueueSet(BufferNode::Allocator* allocator);
~PtrQueueSet();
// Discard any buffered enqueued data.
void reset_queue(PtrQueue& queue);
// If queue has any buffered enqueued data, transfer it to this qset.
// Otherwise, deallocate queue's buffer.
void flush_queue(PtrQueue& queue);
// Add value to queue's buffer, returning true. If buffer is full
// or if queue doesn't have a buffer, does nothing and returns false.
bool try_enqueue(PtrQueue& queue, void* value);
// Add value to queue's buffer. The queue must have a non-full buffer.
// Used after an initial try_enqueue has failed and the situation resolved.
void retry_enqueue(PtrQueue& queue, void* value);
// Installs a new buffer into queue.
// Returns the old buffer, or null if queue didn't have a buffer.
BufferNode* exchange_buffer_with_new(PtrQueue& queue);
// Installs a new buffer into queue.
void install_new_buffer(PtrQueue& queue);
public:
// Return the associated BufferNode allocator.
BufferNode::Allocator* allocator() const { return _allocator; }
// Return the buffer for a BufferNode of size buffer_size().
void** allocate_buffer();
// Return an empty buffer to the free list. The node is required
// to have been allocated with a size of buffer_size().
void deallocate_buffer(BufferNode* node);
// A completed buffer is a buffer the mutator is finished with, and
// is ready to be processed by the collector. It need not be full.
// Adds node to the completed buffer list.
virtual void enqueue_completed_buffer(BufferNode* node) = 0;
size_t buffer_size() const {
return _allocator->buffer_size();
}
};
#endif // SHARE_GC_SHARED_PTRQUEUE_HPP
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