diff -r 4ebc2e2fb97c -r 71c04702a3d5 src/hotspot/share/gc/g1/ptrQueue.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/g1/ptrQueue.cpp	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,308 @@
+/*
+ * Copyright (c) 2001, 2017, 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/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"
+
+#include <new>
+
+PtrQueue::PtrQueue(PtrQueueSet* qset, bool permanent, bool active) :
+  _qset(qset),
+  _active(active),
+  _permanent(permanent),
+  _index(0),
+  _capacity_in_bytes(0),
+  _buf(NULL),
+  _lock(NULL)
+{}
+
+PtrQueue::~PtrQueue() {
+  assert(_permanent || (_buf == NULL), "queue must be flushed before delete");
+}
+
+void PtrQueue::flush_impl() {
+  if (_buf != NULL) {
+    BufferNode* node = BufferNode::make_node_from_buffer(_buf, index());
+    if (is_empty()) {
+      // No work to do.
+      qset()->deallocate_buffer(node);
+    } else {
+      qset()->enqueue_complete_buffer(node);
+    }
+    _buf = NULL;
+    set_index(0);
+  }
+}
+
+
+void PtrQueue::enqueue_known_active(void* ptr) {
+  while (_index == 0) {
+    handle_zero_index();
+  }
+
+  assert(_buf != NULL, "postcondition");
+  assert(index() > 0, "postcondition");
+  assert(index() <= capacity(), "invariant");
+  _index -= _element_size;
+  _buf[index()] = ptr;
+}
+
+void PtrQueue::locking_enqueue_completed_buffer(BufferNode* node) {
+  assert(_lock->owned_by_self(), "Required.");
+  qset()->enqueue_complete_buffer(node);
+}
+
+
+BufferNode* BufferNode::allocate(size_t size) {
+  size_t byte_size = size * sizeof(void*);
+  void* data = NEW_C_HEAP_ARRAY(char, buffer_offset() + byte_size, mtGC);
+  return new (data) BufferNode;
+}
+
+void BufferNode::deallocate(BufferNode* node) {
+  node->~BufferNode();
+  FREE_C_HEAP_ARRAY(char, node);
+}
+
+PtrQueueSet::PtrQueueSet(bool notify_when_complete) :
+  _buffer_size(0),
+  _max_completed_queue(0),
+  _cbl_mon(NULL), _fl_lock(NULL),
+  _notify_when_complete(notify_when_complete),
+  _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;
+}
+
+PtrQueueSet::~PtrQueueSet() {
+  // There are presently only a couple (derived) instances ever
+  // created, and they are permanent, so no harm currently done by
+  // doing nothing here.
+}
+
+void PtrQueueSet::initialize(Monitor* cbl_mon,
+                             Mutex* fl_lock,
+                             int process_completed_threshold,
+                             int max_completed_queue,
+                             PtrQueueSet *fl_owner) {
+  _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;
+}
+
+void** PtrQueueSet::allocate_buffer() {
+  BufferNode* node = NULL;
+  {
+    MutexLockerEx x(_fl_owner->_fl_lock, Mutex::_no_safepoint_check_flag);
+    node = _fl_owner->_buf_free_list;
+    if (node != NULL) {
+      _fl_owner->_buf_free_list = node->next();
+      _fl_owner->_buf_free_list_sz--;
+    }
+  }
+  if (node == NULL) {
+    node = BufferNode::allocate(buffer_size());
+  } else {
+    // Reinitialize buffer obtained from free list.
+    node->set_index(0);
+    node->set_next(NULL);
+  }
+  return BufferNode::make_buffer_from_node(node);
+}
+
+void PtrQueueSet::deallocate_buffer(BufferNode* node) {
+  MutexLockerEx x(_fl_owner->_fl_lock, Mutex::_no_safepoint_check_flag);
+  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;
+  for (size_t i = 0; i < n; ++i) {
+    assert(_buf_free_list != NULL,
+           "_buf_free_list_sz is wrong: " SIZE_FORMAT, _buf_free_list_sz);
+    BufferNode* node = _buf_free_list;
+    _buf_free_list = node->next();
+    _buf_free_list_sz--;
+    BufferNode::deallocate(node);
+  }
+}
+
+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.");
+
+      BufferNode* node = BufferNode::make_node_from_buffer(_buf, index());
+      _buf = NULL;         // clear shared _buf field
+
+      locking_enqueue_completed_buffer(node); // enqueue completed buffer
+      assert(_buf == NULL, "multiple enqueuers appear to be racing");
+    } else {
+      BufferNode* node = BufferNode::make_node_from_buffer(_buf, index());
+      if (qset()->process_or_enqueue_complete_buffer(node)) {
+        // Recycle the buffer. No allocation.
+        assert(_buf == BufferNode::make_buffer_from_node(node), "invariant");
+        assert(capacity() == qset()->buffer_size(), "invariant");
+        reset();
+        return;
+      }
+    }
+  }
+  // Set capacity in case this is the first allocation.
+  set_capacity(qset()->buffer_size());
+  // Allocate a new buffer.
+  _buf = qset()->allocate_buffer();
+  reset();
+}
+
+bool PtrQueueSet::process_or_enqueue_complete_buffer(BufferNode* node) {
+  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(node);
+      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(node);
+  return false;
+}
+
+void PtrQueueSet::enqueue_complete_buffer(BufferNode* cbn) {
+  MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
+  cbn->set_next(NULL);
+  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 >= (size_t)_process_completed_threshold) {
+    _process_completed = true;
+    if (_notify_when_complete) {
+      _cbl_mon->notify();
+    }
+  }
+  DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked());
+}
+
+size_t PtrQueueSet::completed_buffers_list_length() {
+  size_t 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(_buffer_size == 0 && sz > 0, "Should be called only once.");
+  _buffer_size = sz;
+}
+
+// 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);
+  assert(_process_completed_threshold >= 0, "_process_completed is negative");
+  if (_n_completed_buffers >= (size_t)_process_completed_threshold || _max_completed_queue == 0) {
+    _process_completed = true;
+    if (_notify_when_complete)
+      _cbl_mon->notify();
+  }
+}