--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/shared/taskqueue.cpp	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,267 @@
+/*
+ * Copyright (c) 2001, 2016, 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/shared/taskqueue.hpp"
+#include "oops/oop.inline.hpp"
+#include "logging/log.hpp"
+#include "runtime/atomic.hpp"
+#include "runtime/os.hpp"
+#include "runtime/thread.inline.hpp"
+#include "utilities/debug.hpp"
+#include "utilities/stack.inline.hpp"
+
+#ifdef TRACESPINNING
+uint ParallelTaskTerminator::_total_yields = 0;
+uint ParallelTaskTerminator::_total_spins = 0;
+uint ParallelTaskTerminator::_total_peeks = 0;
+#endif
+
+#if TASKQUEUE_STATS
+const char * const TaskQueueStats::_names[last_stat_id] = {
+  "qpush", "qpop", "qpop-s", "qattempt", "qsteal", "opush", "omax"
+};
+
+TaskQueueStats & TaskQueueStats::operator +=(const TaskQueueStats & addend)
+{
+  for (unsigned int i = 0; i < last_stat_id; ++i) {
+    _stats[i] += addend._stats[i];
+  }
+  return *this;
+}
+
+void TaskQueueStats::print_header(unsigned int line, outputStream* const stream,
+                                  unsigned int width)
+{
+  // Use a width w: 1 <= w <= max_width
+  const unsigned int max_width = 40;
+  const unsigned int w = MAX2(MIN2(width, max_width), 1U);
+
+  if (line == 0) { // spaces equal in width to the header
+    const unsigned int hdr_width = w * last_stat_id + last_stat_id - 1;
+    stream->print("%*s", hdr_width, " ");
+  } else if (line == 1) { // labels
+    stream->print("%*s", w, _names[0]);
+    for (unsigned int i = 1; i < last_stat_id; ++i) {
+      stream->print(" %*s", w, _names[i]);
+    }
+  } else if (line == 2) { // dashed lines
+    char dashes[max_width + 1];
+    memset(dashes, '-', w);
+    dashes[w] = '\0';
+    stream->print("%s", dashes);
+    for (unsigned int i = 1; i < last_stat_id; ++i) {
+      stream->print(" %s", dashes);
+    }
+  }
+}
+
+void TaskQueueStats::print(outputStream* stream, unsigned int width) const
+{
+  #define FMT SIZE_FORMAT_W(*)
+  stream->print(FMT, width, _stats[0]);
+  for (unsigned int i = 1; i < last_stat_id; ++i) {
+    stream->print(" " FMT, width, _stats[i]);
+  }
+  #undef FMT
+}
+
+#ifdef ASSERT
+// Invariants which should hold after a TaskQueue has been emptied and is
+// quiescent; they do not hold at arbitrary times.
+void TaskQueueStats::verify() const
+{
+  assert(get(push) == get(pop) + get(steal),
+         "push=" SIZE_FORMAT " pop=" SIZE_FORMAT " steal=" SIZE_FORMAT,
+         get(push), get(pop), get(steal));
+  assert(get(pop_slow) <= get(pop),
+         "pop_slow=" SIZE_FORMAT " pop=" SIZE_FORMAT,
+         get(pop_slow), get(pop));
+  assert(get(steal) <= get(steal_attempt),
+         "steal=" SIZE_FORMAT " steal_attempt=" SIZE_FORMAT,
+         get(steal), get(steal_attempt));
+  assert(get(overflow) == 0 || get(push) != 0,
+         "overflow=" SIZE_FORMAT " push=" SIZE_FORMAT,
+         get(overflow), get(push));
+  assert(get(overflow_max_len) == 0 || get(overflow) != 0,
+         "overflow_max_len=" SIZE_FORMAT " overflow=" SIZE_FORMAT,
+         get(overflow_max_len), get(overflow));
+}
+#endif // ASSERT
+#endif // TASKQUEUE_STATS
+
+int TaskQueueSetSuper::randomParkAndMiller(int *seed0) {
+  const int a =      16807;
+  const int m = 2147483647;
+  const int q =     127773;  /* m div a */
+  const int r =       2836;  /* m mod a */
+  assert(sizeof(int) == 4, "I think this relies on that");
+  int seed = *seed0;
+  int hi   = seed / q;
+  int lo   = seed % q;
+  int test = a * lo - r * hi;
+  if (test > 0)
+    seed = test;
+  else
+    seed = test + m;
+  *seed0 = seed;
+  return seed;
+}
+
+ParallelTaskTerminator::
+ParallelTaskTerminator(uint n_threads, TaskQueueSetSuper* queue_set) :
+  _n_threads(n_threads),
+  _queue_set(queue_set),
+  _offered_termination(0) {}
+
+bool ParallelTaskTerminator::peek_in_queue_set() {
+  return _queue_set->peek();
+}
+
+void ParallelTaskTerminator::yield() {
+  assert(_offered_termination <= _n_threads, "Invariant");
+  os::naked_yield();
+}
+
+void ParallelTaskTerminator::sleep(uint millis) {
+  assert(_offered_termination <= _n_threads, "Invariant");
+  os::sleep(Thread::current(), millis, false);
+}
+
+bool
+ParallelTaskTerminator::offer_termination(TerminatorTerminator* terminator) {
+  assert(_n_threads > 0, "Initialization is incorrect");
+  assert(_offered_termination < _n_threads, "Invariant");
+  Atomic::inc((int *)&_offered_termination);
+
+  uint yield_count = 0;
+  // Number of hard spin loops done since last yield
+  uint hard_spin_count = 0;
+  // Number of iterations in the hard spin loop.
+  uint hard_spin_limit = WorkStealingHardSpins;
+
+  // If WorkStealingSpinToYieldRatio is 0, no hard spinning is done.
+  // If it is greater than 0, then start with a small number
+  // of spins and increase number with each turn at spinning until
+  // the count of hard spins exceeds WorkStealingSpinToYieldRatio.
+  // Then do a yield() call and start spinning afresh.
+  if (WorkStealingSpinToYieldRatio > 0) {
+    hard_spin_limit = WorkStealingHardSpins >> WorkStealingSpinToYieldRatio;
+    hard_spin_limit = MAX2(hard_spin_limit, 1U);
+  }
+  // Remember the initial spin limit.
+  uint hard_spin_start = hard_spin_limit;
+
+  // Loop waiting for all threads to offer termination or
+  // more work.
+  while (true) {
+    assert(_offered_termination <= _n_threads, "Invariant");
+    // Are all threads offering termination?
+    if (_offered_termination == _n_threads) {
+      return true;
+    } else {
+      // Look for more work.
+      // Periodically sleep() instead of yield() to give threads
+      // waiting on the cores the chance to grab this code
+      if (yield_count <= WorkStealingYieldsBeforeSleep) {
+        // Do a yield or hardspin.  For purposes of deciding whether
+        // to sleep, count this as a yield.
+        yield_count++;
+
+        // Periodically call yield() instead spinning
+        // After WorkStealingSpinToYieldRatio spins, do a yield() call
+        // and reset the counts and starting limit.
+        if (hard_spin_count > WorkStealingSpinToYieldRatio) {
+          yield();
+          hard_spin_count = 0;
+          hard_spin_limit = hard_spin_start;
+#ifdef TRACESPINNING
+          _total_yields++;
+#endif
+        } else {
+          // Hard spin this time
+          // Increase the hard spinning period but only up to a limit.
+          hard_spin_limit = MIN2(2*hard_spin_limit,
+                                 (uint) WorkStealingHardSpins);
+          for (uint j = 0; j < hard_spin_limit; j++) {
+            SpinPause();
+          }
+          hard_spin_count++;
+#ifdef TRACESPINNING
+          _total_spins++;
+#endif
+        }
+      } else {
+        log_develop_trace(gc, task)("ParallelTaskTerminator::offer_termination() thread " PTR_FORMAT " sleeps after %u yields",
+                                    p2i(Thread::current()), yield_count);
+        yield_count = 0;
+        // A sleep will cause this processor to seek work on another processor's
+        // runqueue, if it has nothing else to run (as opposed to the yield
+        // which may only move the thread to the end of the this processor's
+        // runqueue).
+        sleep(WorkStealingSleepMillis);
+      }
+
+#ifdef TRACESPINNING
+      _total_peeks++;
+#endif
+      if (peek_in_queue_set() ||
+          (terminator != NULL && terminator->should_exit_termination())) {
+        Atomic::dec((int *)&_offered_termination);
+        assert(_offered_termination < _n_threads, "Invariant");
+        return false;
+      }
+    }
+  }
+}
+
+#ifdef TRACESPINNING
+void ParallelTaskTerminator::print_termination_counts() {
+  log_trace(gc, task)("ParallelTaskTerminator Total yields: %u"
+    " Total spins: %u Total peeks: %u",
+    total_yields(),
+    total_spins(),
+    total_peeks());
+}
+#endif
+
+void ParallelTaskTerminator::reset_for_reuse() {
+  if (_offered_termination != 0) {
+    assert(_offered_termination == _n_threads,
+           "Terminator may still be in use");
+    _offered_termination = 0;
+  }
+}
+
+#ifdef ASSERT
+bool ObjArrayTask::is_valid() const {
+  return _obj != NULL && _obj->is_objArray() && _index >= 0 &&
+      _index < objArrayOop(_obj)->length();
+}
+#endif // ASSERT
+
+void ParallelTaskTerminator::reset_for_reuse(uint n_threads) {
+  reset_for_reuse();
+  _n_threads = n_threads;
+}