src/share/vm/gc_implementation/g1/ptrQueue.cpp - platform/external/jetbrains/jdk8u_hotspot - Git at Google

 /*
  * Copyright (c) 2001, 2014, 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.
  *
  */

 #include "precompiled.hpp"
 #include "gc_implementation/g1/ptrQueue.hpp"
 #include "memory/allocation.hpp"
 #include "memory/allocation.inline.hpp"
 #include "runtime/mutex.hpp"
 #include "runtime/mutexLocker.hpp"
 #include "runtime/thread.inline.hpp"

 PtrQueue::PtrQueue(PtrQueueSet* qset, bool perm, bool active) :
   _qset(qset), _buf(NULL), _index(0), _sz(0), _active(active),
   _perm(perm), _lock(NULL)
 {}

 PtrQueue::~PtrQueue() {
   assert(_perm || (_buf == NULL), "queue must be flushed before delete");
 }

 void PtrQueue::flush_impl() {
   if (!_perm && _buf != NULL) {
     if (_index == _sz) {
       // No work to do.
       qset()->deallocate_buffer(_buf);
     } else {
       // We must NULL out the unused entries, then enqueue.
       for (size_t i = 0; i < _index; i += oopSize) {
         _buf[byte_index_to_index((int)i)] = NULL;
       }
       qset()->enqueue_complete_buffer(_buf);
     }
     _buf = NULL;
     _index = 0;
   }
 }


 void PtrQueue::enqueue_known_active(void* ptr) {
   assert(0 <= _index && _index <= _sz, "Invariant.");
   assert(_index == 0 || _buf != NULL, "invariant");

   while (_index == 0) {
     handle_zero_index();
   }

   assert(_index > 0, "postcondition");
   _index -= oopSize;
   _buf[byte_index_to_index((int)_index)] = ptr;
   assert(0 <= _index && _index <= _sz, "Invariant.");
 }

 void PtrQueue::locking_enqueue_completed_buffer(void** buf) {
   assert(_lock->owned_by_self(), "Required.");

   // We have to unlock _lock (which may be Shared_DirtyCardQ_lock) before
   // we acquire DirtyCardQ_CBL_mon inside enqeue_complete_buffer as they
   // have the same rank and we may get the "possible deadlock" message
   _lock->unlock();

   qset()->enqueue_complete_buffer(buf);
   // We must relock only because the caller will unlock, for the normal
   // case.
   _lock->lock_without_safepoint_check();
 }


 PtrQueueSet::PtrQueueSet(bool notify_when_complete) :
   _max_completed_queue(0),
   _cbl_mon(NULL), _fl_lock(NULL),
   _notify_when_complete(notify_when_complete),
   _sz(0),
   _completed_buffers_head(NULL),
   _completed_buffers_tail(NULL),
   _n_completed_buffers(0),
   _process_completed_threshold(0), _process_completed(false),
   _buf_free_list(NULL), _buf_free_list_sz(0)
 {
   _fl_owner = this;
 }

 void** PtrQueueSet::allocate_buffer() {
   assert(_sz > 0, "Didn't set a buffer size.");
   MutexLockerEx x(_fl_owner->_fl_lock, Mutex::_no_safepoint_check_flag);
   if (_fl_owner->_buf_free_list != NULL) {
     void** res = BufferNode::make_buffer_from_node(_fl_owner->_buf_free_list);
     _fl_owner->_buf_free_list = _fl_owner->_buf_free_list->next();
     _fl_owner->_buf_free_list_sz--;
     return res;
   } else {
     // Allocate space for the BufferNode in front of the buffer.
     char *b =  NEW_C_HEAP_ARRAY(char, _sz + BufferNode::aligned_size(), mtGC);
     return BufferNode::make_buffer_from_block(b);
   }
 }

 void PtrQueueSet::deallocate_buffer(void** buf) {
   assert(_sz > 0, "Didn't set a buffer size.");
   MutexLockerEx x(_fl_owner->_fl_lock, Mutex::_no_safepoint_check_flag);
   BufferNode *node = BufferNode::make_node_from_buffer(buf);
   node->set_next(_fl_owner->_buf_free_list);
   _fl_owner->_buf_free_list = node;
   _fl_owner->_buf_free_list_sz++;
 }

 void PtrQueueSet::reduce_free_list() {
   assert(_fl_owner == this, "Free list reduction is allowed only for the owner");
   // For now we'll adopt the strategy of deleting half.
   MutexLockerEx x(_fl_lock, Mutex::_no_safepoint_check_flag);
   size_t n = _buf_free_list_sz / 2;
   while (n > 0) {
     assert(_buf_free_list != NULL, "_buf_free_list_sz must be wrong.");
     void* b = BufferNode::make_block_from_node(_buf_free_list);
     _buf_free_list = _buf_free_list->next();
     FREE_C_HEAP_ARRAY(char, b, mtGC);
     _buf_free_list_sz --;
     n--;
   }
 }

 void PtrQueue::handle_zero_index() {
   assert(_index == 0, "Precondition.");

   // This thread records the full buffer and allocates a new one (while
   // holding the lock if there is one).
   if (_buf != NULL) {
     if (!should_enqueue_buffer()) {
       assert(_index > 0, "the buffer can only be re-used if it's not full");
       return;
     }

     if (_lock) {
       assert(_lock->owned_by_self(), "Required.");

       // The current PtrQ may be the shared dirty card queue and
       // may be being manipulated by more than one worker thread
       // during a pause. Since the enqueuing of the completed
       // buffer unlocks the Shared_DirtyCardQ_lock more than one
       // worker thread can 'race' on reading the shared queue attributes
       // (_buf and _index) and multiple threads can call into this
       // routine for the same buffer. This will cause the completed
       // buffer to be added to the CBL multiple times.

       // We "claim" the current buffer by caching value of _buf in
       // a local and clearing the field while holding _lock. When
       // _lock is released (while enqueueing the completed buffer)
       // the thread that acquires _lock will skip this code,
       // preventing the subsequent the multiple enqueue, and
       // install a newly allocated buffer below.

       void** buf = _buf;   // local pointer to completed buffer
       _buf = NULL;         // clear shared _buf field

       locking_enqueue_completed_buffer(buf);  // enqueue completed buffer

       // While the current thread was enqueuing the buffer another thread
       // may have a allocated a new buffer and inserted it into this pointer
       // queue. If that happens then we just return so that the current
       // thread doesn't overwrite the buffer allocated by the other thread
       // and potentially losing some dirtied cards.

       if (_buf != NULL) return;
     } else {
       if (qset()->process_or_enqueue_complete_buffer(_buf)) {
         // Recycle the buffer. No allocation.
         _sz = qset()->buffer_size();
         _index = _sz;
         return;
       }
     }
   }
   // Reallocate the buffer
   _buf = qset()->allocate_buffer();
   _sz = qset()->buffer_size();
   _index = _sz;
   assert(0 <= _index && _index <= _sz, "Invariant.");
 }

 bool PtrQueueSet::process_or_enqueue_complete_buffer(void** buf) {
   if (Thread::current()->is_Java_thread()) {
     // We don't lock. It is fine to be epsilon-precise here.
     if (_max_completed_queue == 0 || _max_completed_queue > 0 &&
         _n_completed_buffers >= _max_completed_queue + _completed_queue_padding) {
       bool b = mut_process_buffer(buf);
       if (b) {
         // True here means that the buffer hasn't been deallocated and the caller may reuse it.
         return true;
       }
     }
   }
   // The buffer will be enqueued. The caller will have to get a new one.
   enqueue_complete_buffer(buf);
   return false;
 }

 void PtrQueueSet::enqueue_complete_buffer(void** buf, size_t index) {
   MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
   BufferNode* cbn = BufferNode::new_from_buffer(buf);
   cbn->set_index(index);
   if (_completed_buffers_tail == NULL) {
     assert(_completed_buffers_head == NULL, "Well-formedness");
     _completed_buffers_head = cbn;
     _completed_buffers_tail = cbn;
   } else {
     _completed_buffers_tail->set_next(cbn);
     _completed_buffers_tail = cbn;
   }
   _n_completed_buffers++;

   if (!_process_completed && _process_completed_threshold >= 0 &&
       _n_completed_buffers >= _process_completed_threshold) {
     _process_completed = true;
     if (_notify_when_complete)
       _cbl_mon->notify();
   }
   debug_only(assert_completed_buffer_list_len_correct_locked());
 }

 int PtrQueueSet::completed_buffers_list_length() {
   int n = 0;
   BufferNode* cbn = _completed_buffers_head;
   while (cbn != NULL) {
     n++;
     cbn = cbn->next();
   }
   return n;
 }

 void PtrQueueSet::assert_completed_buffer_list_len_correct() {
   MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
   assert_completed_buffer_list_len_correct_locked();
 }

 void PtrQueueSet::assert_completed_buffer_list_len_correct_locked() {
   guarantee(completed_buffers_list_length() ==  _n_completed_buffers,
             "Completed buffer length is wrong.");
 }

 void PtrQueueSet::set_buffer_size(size_t sz) {
   assert(_sz == 0 && sz > 0, "Should be called only once.");
   _sz = sz * oopSize;
 }

 // Merge lists of buffers. Notify the processing threads.
 // The source queue is emptied as a result. The queues
 // must share the monitor.
 void PtrQueueSet::merge_bufferlists(PtrQueueSet *src) {
   assert(_cbl_mon == src->_cbl_mon, "Should share the same lock");
   MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
   if (_completed_buffers_tail == NULL) {
     assert(_completed_buffers_head == NULL, "Well-formedness");
     _completed_buffers_head = src->_completed_buffers_head;
     _completed_buffers_tail = src->_completed_buffers_tail;
   } else {
     assert(_completed_buffers_head != NULL, "Well formedness");
     if (src->_completed_buffers_head != NULL) {
       _completed_buffers_tail->set_next(src->_completed_buffers_head);
       _completed_buffers_tail = src->_completed_buffers_tail;
     }
   }
   _n_completed_buffers += src->_n_completed_buffers;

   src->_n_completed_buffers = 0;
   src->_completed_buffers_head = NULL;
   src->_completed_buffers_tail = NULL;

   assert(_completed_buffers_head == NULL && _completed_buffers_tail == NULL ||
          _completed_buffers_head != NULL && _completed_buffers_tail != NULL,
          "Sanity");
 }

 void PtrQueueSet::notify_if_necessary() {
   MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
   if (_n_completed_buffers >= _process_completed_threshold || _max_completed_queue == 0) {
     _process_completed = true;
     if (_notify_when_complete)
       _cbl_mon->notify();
   }
 }
	/*
	* Copyright (c) 2001, 2014, 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.
	*
	*/

	#include "precompiled.hpp"
	#include "gc_implementation/g1/ptrQueue.hpp"
	#include "memory/allocation.hpp"
	#include "memory/allocation.inline.hpp"
	#include "runtime/mutex.hpp"
	#include "runtime/mutexLocker.hpp"
	#include "runtime/thread.inline.hpp"

	PtrQueue::PtrQueue(PtrQueueSet* qset, bool perm, bool active) :
	_qset(qset), _buf(NULL), _index(0), _sz(0), _active(active),
	_perm(perm), _lock(NULL)
	{}

	PtrQueue::~PtrQueue() {
	assert(_perm \|\| (_buf == NULL), "queue must be flushed before delete");
	}

	void PtrQueue::flush_impl() {
	if (!_perm && _buf != NULL) {
	if (_index == _sz) {
	// No work to do.
	qset()->deallocate_buffer(_buf);
	} else {
	// We must NULL out the unused entries, then enqueue.
	for (size_t i = 0; i < _index; i += oopSize) {
	_buf[byte_index_to_index((int)i)] = NULL;
	}
	qset()->enqueue_complete_buffer(_buf);
	}
	_buf = NULL;
	_index = 0;
	}
	}


	void PtrQueue::enqueue_known_active(void* ptr) {
	assert(0 <= _index && _index <= _sz, "Invariant.");
	assert(_index == 0 \|\| _buf != NULL, "invariant");

	while (_index == 0) {
	handle_zero_index();
	}

	assert(_index > 0, "postcondition");
	_index -= oopSize;
	_buf[byte_index_to_index((int)_index)] = ptr;
	assert(0 <= _index && _index <= _sz, "Invariant.");
	}

	void PtrQueue::locking_enqueue_completed_buffer(void** buf) {
	assert(_lock->owned_by_self(), "Required.");

	// We have to unlock _lock (which may be Shared_DirtyCardQ_lock) before
	// we acquire DirtyCardQ_CBL_mon inside enqeue_complete_buffer as they
	// have the same rank and we may get the "possible deadlock" message
	_lock->unlock();

	qset()->enqueue_complete_buffer(buf);
	// We must relock only because the caller will unlock, for the normal
	// case.
	_lock->lock_without_safepoint_check();
	}


	PtrQueueSet::PtrQueueSet(bool notify_when_complete) :
	_max_completed_queue(0),
	_cbl_mon(NULL), _fl_lock(NULL),
	_notify_when_complete(notify_when_complete),
	_sz(0),
	_completed_buffers_head(NULL),
	_completed_buffers_tail(NULL),
	_n_completed_buffers(0),
	_process_completed_threshold(0), _process_completed(false),
	_buf_free_list(NULL), _buf_free_list_sz(0)
	{
	_fl_owner = this;
	}

	void** PtrQueueSet::allocate_buffer() {
	assert(_sz > 0, "Didn't set a buffer size.");
	MutexLockerEx x(_fl_owner->_fl_lock, Mutex::_no_safepoint_check_flag);
	if (_fl_owner->_buf_free_list != NULL) {
	void** res = BufferNode::make_buffer_from_node(_fl_owner->_buf_free_list);
	_fl_owner->_buf_free_list = _fl_owner->_buf_free_list->next();
	_fl_owner->_buf_free_list_sz--;
	return res;
	} else {
	// Allocate space for the BufferNode in front of the buffer.
	char *b = NEW_C_HEAP_ARRAY(char, _sz + BufferNode::aligned_size(), mtGC);
	return BufferNode::make_buffer_from_block(b);
	}
	}

	void PtrQueueSet::deallocate_buffer(void** buf) {
	assert(_sz > 0, "Didn't set a buffer size.");
	MutexLockerEx x(_fl_owner->_fl_lock, Mutex::_no_safepoint_check_flag);
	BufferNode *node = BufferNode::make_node_from_buffer(buf);
	node->set_next(_fl_owner->_buf_free_list);
	_fl_owner->_buf_free_list = node;
	_fl_owner->_buf_free_list_sz++;
	}

	void PtrQueueSet::reduce_free_list() {
	assert(_fl_owner == this, "Free list reduction is allowed only for the owner");
	// For now we'll adopt the strategy of deleting half.
	MutexLockerEx x(_fl_lock, Mutex::_no_safepoint_check_flag);
	size_t n = _buf_free_list_sz / 2;
	while (n > 0) {
	assert(_buf_free_list != NULL, "_buf_free_list_sz must be wrong.");
	void* b = BufferNode::make_block_from_node(_buf_free_list);
	_buf_free_list = _buf_free_list->next();
	FREE_C_HEAP_ARRAY(char, b, mtGC);
	_buf_free_list_sz --;
	n--;
	}
	}

	void PtrQueue::handle_zero_index() {
	assert(_index == 0, "Precondition.");

	// This thread records the full buffer and allocates a new one (while
	// holding the lock if there is one).
	if (_buf != NULL) {
	if (!should_enqueue_buffer()) {
	assert(_index > 0, "the buffer can only be re-used if it's not full");
	return;
	}

	if (_lock) {
	assert(_lock->owned_by_self(), "Required.");

	// The current PtrQ may be the shared dirty card queue and
	// may be being manipulated by more than one worker thread
	// during a pause. Since the enqueuing of the completed
	// buffer unlocks the Shared_DirtyCardQ_lock more than one
	// worker thread can 'race' on reading the shared queue attributes
	// (_buf and _index) and multiple threads can call into this
	// routine for the same buffer. This will cause the completed
	// buffer to be added to the CBL multiple times.

	// We "claim" the current buffer by caching value of _buf in
	// a local and clearing the field while holding _lock. When
	// _lock is released (while enqueueing the completed buffer)
	// the thread that acquires _lock will skip this code,
	// preventing the subsequent the multiple enqueue, and
	// install a newly allocated buffer below.

	void** buf = _buf; // local pointer to completed buffer
	_buf = NULL; // clear shared _buf field

	locking_enqueue_completed_buffer(buf); // enqueue completed buffer

	// While the current thread was enqueuing the buffer another thread
	// may have a allocated a new buffer and inserted it into this pointer
	// queue. If that happens then we just return so that the current
	// thread doesn't overwrite the buffer allocated by the other thread
	// and potentially losing some dirtied cards.

	if (_buf != NULL) return;
	} else {
	if (qset()->process_or_enqueue_complete_buffer(_buf)) {
	// Recycle the buffer. No allocation.
	_sz = qset()->buffer_size();
	_index = _sz;
	return;
	}
	}
	}
	// Reallocate the buffer
	_buf = qset()->allocate_buffer();
	_sz = qset()->buffer_size();
	_index = _sz;
	assert(0 <= _index && _index <= _sz, "Invariant.");
	}

	bool PtrQueueSet::process_or_enqueue_complete_buffer(void** buf) {
	if (Thread::current()->is_Java_thread()) {
	// We don't lock. It is fine to be epsilon-precise here.
	if (_max_completed_queue == 0 \|\| _max_completed_queue > 0 &&
	_n_completed_buffers >= _max_completed_queue + _completed_queue_padding) {
	bool b = mut_process_buffer(buf);
	if (b) {
	// True here means that the buffer hasn't been deallocated and the caller may reuse it.
	return true;
	}
	}
	}
	// The buffer will be enqueued. The caller will have to get a new one.
	enqueue_complete_buffer(buf);
	return false;
	}

	void PtrQueueSet::enqueue_complete_buffer(void** buf, size_t index) {
	MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
	BufferNode* cbn = BufferNode::new_from_buffer(buf);
	cbn->set_index(index);
	if (_completed_buffers_tail == NULL) {
	assert(_completed_buffers_head == NULL, "Well-formedness");
	_completed_buffers_head = cbn;
	_completed_buffers_tail = cbn;
	} else {
	_completed_buffers_tail->set_next(cbn);
	_completed_buffers_tail = cbn;
	}
	_n_completed_buffers++;

	if (!_process_completed && _process_completed_threshold >= 0 &&
	_n_completed_buffers >= _process_completed_threshold) {
	_process_completed = true;
	if (_notify_when_complete)
	_cbl_mon->notify();
	}
	debug_only(assert_completed_buffer_list_len_correct_locked());
	}

	int PtrQueueSet::completed_buffers_list_length() {
	int n = 0;
	BufferNode* cbn = _completed_buffers_head;
	while (cbn != NULL) {
	n++;
	cbn = cbn->next();
	}
	return n;
	}

	void PtrQueueSet::assert_completed_buffer_list_len_correct() {
	MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
	assert_completed_buffer_list_len_correct_locked();
	}

	void PtrQueueSet::assert_completed_buffer_list_len_correct_locked() {
	guarantee(completed_buffers_list_length() == _n_completed_buffers,
	"Completed buffer length is wrong.");
	}

	void PtrQueueSet::set_buffer_size(size_t sz) {
	assert(_sz == 0 && sz > 0, "Should be called only once.");
	_sz = sz * oopSize;
	}

	// Merge lists of buffers. Notify the processing threads.
	// The source queue is emptied as a result. The queues
	// must share the monitor.
	void PtrQueueSet::merge_bufferlists(PtrQueueSet *src) {
	assert(_cbl_mon == src->_cbl_mon, "Should share the same lock");
	MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
	if (_completed_buffers_tail == NULL) {
	assert(_completed_buffers_head == NULL, "Well-formedness");
	_completed_buffers_head = src->_completed_buffers_head;
	_completed_buffers_tail = src->_completed_buffers_tail;
	} else {
	assert(_completed_buffers_head != NULL, "Well formedness");
	if (src->_completed_buffers_head != NULL) {
	_completed_buffers_tail->set_next(src->_completed_buffers_head);
	_completed_buffers_tail = src->_completed_buffers_tail;
	}
	}
	_n_completed_buffers += src->_n_completed_buffers;

	src->_n_completed_buffers = 0;
	src->_completed_buffers_head = NULL;
	src->_completed_buffers_tail = NULL;

	assert(_completed_buffers_head == NULL && _completed_buffers_tail == NULL \|\|
	_completed_buffers_head != NULL && _completed_buffers_tail != NULL,
	"Sanity");
	}

	void PtrQueueSet::notify_if_necessary() {
	MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
	if (_n_completed_buffers >= _process_completed_threshold \|\| _max_completed_queue == 0) {
	_process_completed = true;
	if (_notify_when_complete)
	_cbl_mon->notify();
	}
	}