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 /*

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  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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  * 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_VM_GC_IMPLEMENTATION_G1_PTRQUEUE_HPP

 #define SHARE_VM_GC_IMPLEMENTATION_G1_PTRQUEUE_HPP

 #include "memory/allocation.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.

 // The definition of placement operator new(size_t, void*) in the <new>.

 #include <new>

 class PtrQueueSet;

 class PtrQueue VALUE_OBJ_CLASS_SPEC {

   friend class VMStructs;

 protected:

   // The ptr queue set to which this queue belongs.

   PtrQueueSet* _qset;

   // Whether updates should be logged.

   bool _active;

   // The buffer.

   void** _buf;

   // The index at which an object was last enqueued.  Starts at "_sz"

   // (indicating an empty buffer) and goes towards zero.

   size_t _index;

   // The size of the buffer.

   size_t _sz;

   // If true, the queue is permanent, and doesn't need to deallocate

   // its buffer in the destructor (since that obtains a lock which may not

   // be legally locked by then.

   bool _perm;

   // If there is a lock associated with this buffer, this is that lock.

   Mutex* _lock;

   PtrQueueSet* qset() { return _qset; }

   bool is_permanent() const { return _perm; }

   // Process queue entries and release resources, if not permanent.

   void flush_impl();

 public:

   // Initialize this queue to contain a null buffer, and be part of the

   // given PtrQueueSet.

   PtrQueue(PtrQueueSet* qset, bool perm = false, bool active = false);

   // Requires queue flushed or permanent.

   ~PtrQueue();

   // Associate a lock with a ptr queue.

   void set_lock(Mutex* lock) { _lock = lock; }

   void reset() { if (_buf != NULL) _index = _sz; }

   void enqueue(volatile void* ptr) {

     enqueue((void*)(ptr));

   }

   // Enqueues the given "obj".

   void enqueue(void* ptr) {

     if (!_active) return;

     else enqueue_known_active(ptr);

   }

   // This method is called when we're doing the zero index handling

   // and gives a chance to the queues to do any pre-enqueueing

   // processing they might want to do on the buffer. It should return

   // true if the buffer should be enqueued, or false if enough

   // entries were cleared from it so that it can be re-used. It should

   // not return false if the buffer is still full (otherwise we can

   // get into an infinite loop).

   virtual bool should_enqueue_buffer() { return true; }

   void handle_zero_index();

   void locking_enqueue_completed_buffer(void** buf);

   void enqueue_known_active(void* ptr);

   size_t size() {

     assert(_sz >= _index, "Invariant.");

     return _buf == NULL ? 0 : _sz - _index;

   }

   bool is_empty() {

     return _buf == NULL || _sz == _index;

   }

   // Set the "active" property of the queue to "b".  An enqueue to an

   // inactive thread is a no-op.  Setting a queue to inactive resets its

   // log to the empty state.

   void set_active(bool b) {

     _active = b;

     if (!b && _buf != NULL) {

       _index = _sz;

     } else if (b && _buf != NULL) {

       assert(_index == _sz, "invariant: queues are empty when activated.");

     }

   }

   bool is_active() { return _active; }

   static int byte_index_to_index(int ind) {

     assert((ind % oopSize) == 0, "Invariant.");

     return ind / oopSize;

   }

   static int index_to_byte_index(int byte_ind) {

     return byte_ind * oopSize;

   }

   // To support compiler.

   static ByteSize byte_offset_of_index() {

     return byte_offset_of(PtrQueue, _index);

   }

   static ByteSize byte_width_of_index() { return in_ByteSize(sizeof(size_t)); }

   static ByteSize byte_offset_of_buf() {

     return byte_offset_of(PtrQueue, _buf);

   }

   static ByteSize byte_width_of_buf() { return in_ByteSize(sizeof(void*)); }

   static ByteSize byte_offset_of_active() {

     return byte_offset_of(PtrQueue, _active);

   }

   static ByteSize byte_width_of_active() { return in_ByteSize(sizeof(bool)); }

 };

 class BufferNode {

   size_t _index;

   BufferNode* _next;

 public:

   BufferNode() : _index(0), _next(NULL) { }

   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;    }

   // Align the size of the structure to the size of the pointer

   static size_t aligned_size() {

     static const size_t alignment = round_to(sizeof(BufferNode), sizeof(void*));

     return alignment;

   }

   // BufferNode is allocated before the buffer.

   // The chunk of memory that holds both of them is a block.

   // Produce a new BufferNode given a buffer.

   static BufferNode* new_from_buffer(void** buf) {

     return new (make_block_from_buffer(buf)) BufferNode;

   }

   // The following are the required conversion routines:

   static BufferNode* make_node_from_buffer(void** buf) {

     return (BufferNode*)make_block_from_buffer(buf);

   }

   static void** make_buffer_from_node(BufferNode *node) {

     return make_buffer_from_block(node);

   }

   static void* make_block_from_node(BufferNode *node) {

     return (void*)node;

   }

   static void** make_buffer_from_block(void* p) {

     return (void**)((char*)p + aligned_size());

   }

   static void* make_block_from_buffer(void** p) {

     return (void*)((char*)p - aligned_size());

   }

 };

 // 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.

 // All these variables are are protected by the TLOQ_CBL_mon. XXX ???

 class PtrQueueSet VALUE_OBJ_CLASS_SPEC {

 protected:

   Monitor* _cbl_mon;  // Protects the fields below.

   BufferNode* _completed_buffers_head;

   BufferNode* _completed_buffers_tail;

   int _n_completed_buffers;

   int _process_completed_threshold;

   volatile bool _process_completed;

   // This (and the interpretation of the first element as a "next"

   // pointer) are protected by the TLOQ_FL_lock.

   Mutex* _fl_lock;

   BufferNode* _buf_free_list;

   size_t _buf_free_list_sz;

   // Queue set can share a freelist. The _fl_owner variable

   // specifies the owner. It is set to "this" by default.

   PtrQueueSet* _fl_owner;

   // The size of all buffers in the set.

   size_t _sz;

   bool _all_active;

   // If true, notify_all on _cbl_mon when the threshold is reached.

   bool _notify_when_complete;

   // Maximum number of elements allowed on completed queue: after that,

   // enqueuer does the work itself.  Zero indicates no maximum.

   int _max_completed_queue;

   int _completed_queue_padding;

   int completed_buffers_list_length();

   void assert_completed_buffer_list_len_correct_locked();

   void assert_completed_buffer_list_len_correct();

 protected:

   // A mutator thread does the the work of processing a buffer.

   // Returns "true" iff the work is complete (and the buffer may be

   // deallocated).

   virtual bool mut_process_buffer(void** buf) {

     ShouldNotReachHere();

     return false;

   }

 public:

   // Create an empty ptr queue set.

   PtrQueueSet(bool notify_when_complete = false);

   // Because of init-order concerns, we can't pass these as constructor

   // arguments.

   void initialize(Monitor* cbl_mon, Mutex* fl_lock,

                   int process_completed_threshold,

                   int max_completed_queue,

                   PtrQueueSet *fl_owner = NULL) {

     _max_completed_queue = max_completed_queue;

     _process_completed_threshold = process_completed_threshold;

     _completed_queue_padding = 0;

     assert(cbl_mon != NULL && fl_lock != NULL, "Init order issue?");

     _cbl_mon = cbl_mon;

     _fl_lock = fl_lock;

     _fl_owner = (fl_owner != NULL) ? fl_owner : this;

   }

   // Return an empty oop array of size _sz (required to be non-zero).

   void** allocate_buffer();

   // Return an empty buffer to the free list.  The "buf" argument is

   // required to be a pointer to the head of an array of length "_sz".

   void deallocate_buffer(void** buf);

   // Declares that "buf" is a complete buffer.

   void enqueue_complete_buffer(void** buf, size_t index = 0);

   // To be invoked by the mutator.

   bool process_or_enqueue_complete_buffer(void** buf);

   bool completed_buffers_exist_dirty() {

     return _n_completed_buffers > 0;

   }

   bool process_completed_buffers() { return _process_completed; }

   void set_process_completed(bool x) { _process_completed = x; }

   bool is_active() { return _all_active; }

   // Set the buffer size.  Should be called before any "enqueue" operation

   // can be called.  And should only be called once.

   void set_buffer_size(size_t sz);

   // Get the buffer size.

   size_t buffer_size() { return _sz; }

   // Get/Set the number of completed buffers that triggers log processing.

   void set_process_completed_threshold(int sz) { _process_completed_threshold = sz; }

   int process_completed_threshold() const { return _process_completed_threshold; }

   // Must only be called at a safe point.  Indicates that the buffer free

   // list size may be reduced, if that is deemed desirable.

   void reduce_free_list();

   int completed_buffers_num() { return _n_completed_buffers; }

   void merge_bufferlists(PtrQueueSet* src);

   void set_max_completed_queue(int m) { _max_completed_queue = m; }

   int max_completed_queue() { return _max_completed_queue; }

   void set_completed_queue_padding(int padding) { _completed_queue_padding = padding; }

   int completed_queue_padding() { return _completed_queue_padding; }

   // Notify the consumer if the number of buffers crossed the threshold

   void notify_if_necessary();

 };

 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_PTRQUEUE_HPP