/*

 * Copyright 2001-2009 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 *

 */

# include "incls/_precompiled.incl"

# include "incls/_taskqueue.cpp.incl"

#ifdef TRACESPINNING

uint ParallelTaskTerminator::_total_yields = 0;

uint ParallelTaskTerminator::_total_spins = 0;

uint ParallelTaskTerminator::_total_peeks = 0;

#endif

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(int 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::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(_offered_termination < _n_threads, "Invariant");

  Atomic::inc(&_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 {

        if (PrintGCDetails && Verbose) {

         gclog_or_tty->print_cr("ParallelTaskTerminator::offer_termination() "

           "thread %d sleeps after %d yields",

           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(&_offered_termination);

        assert(_offered_termination < _n_threads, "Invariant");

        return false;

      }

    }

  }

}

#ifdef TRACESPINNING

void ParallelTaskTerminator::print_termination_counts() {

  gclog_or_tty->print_cr("ParallelTaskTerminator Total yields: %lld  "

    "Total spins: %lld  Total peeks: %lld",

    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;

  }

}

bool RegionTaskQueueWithOverflow::is_empty() {

  return (_region_queue.size() == 0) &&

         (_overflow_stack->length() == 0);

}

bool RegionTaskQueueWithOverflow::stealable_is_empty() {

  return _region_queue.size() == 0;

}

bool RegionTaskQueueWithOverflow::overflow_is_empty() {

  return _overflow_stack->length() == 0;

}

void RegionTaskQueueWithOverflow::initialize() {

  _region_queue.initialize();

  assert(_overflow_stack == 0, "Creating memory leak");

  _overflow_stack =

    new (ResourceObj::C_HEAP) GrowableArray<RegionTask>(10, true);

}

void RegionTaskQueueWithOverflow::save(RegionTask t) {

  if (TraceRegionTasksQueuing && Verbose) {

    gclog_or_tty->print_cr("CTQ: save " PTR_FORMAT, t);

  }

  if(!_region_queue.push(t)) {

    _overflow_stack->push(t);

  }

}

// Note that using this method will retrieve all regions

// that have been saved but that it will always check

// the overflow stack.  It may be more efficient to

// check the stealable queue and the overflow stack

// separately.

bool RegionTaskQueueWithOverflow::retrieve(RegionTask& region_task) {

  bool result = retrieve_from_overflow(region_task);

  if (!result) {

    result = retrieve_from_stealable_queue(region_task);

  }

  if (TraceRegionTasksQueuing && Verbose && result) {

    gclog_or_tty->print_cr("  CTQ: retrieve " PTR_FORMAT, result);

  }

  return result;

}

bool RegionTaskQueueWithOverflow::retrieve_from_stealable_queue(

                                   RegionTask& region_task) {

  bool result = _region_queue.pop_local(region_task);

  if (TraceRegionTasksQueuing && Verbose) {

    gclog_or_tty->print_cr("CTQ: retrieve_stealable " PTR_FORMAT, region_task);

  }

  return result;

}

bool

RegionTaskQueueWithOverflow::retrieve_from_overflow(RegionTask& region_task) {

  bool result;

  if (!_overflow_stack->is_empty()) {

    region_task = _overflow_stack->pop();

    result = true;

  } else {

    region_task = (RegionTask) NULL;

    result = false;

  }

  if (TraceRegionTasksQueuing && Verbose) {

    gclog_or_tty->print_cr("CTQ: retrieve_stealable " PTR_FORMAT, region_task);

  }

  return result;

}