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 /*

  * Copyright (c) 2001, 2009, 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 "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;

   }

 }

 #ifdef ASSERT

 bool ObjArrayTask::is_valid() const {

   return _obj != NULL && _obj->is_objArray() && _index > 0 &&

     _index < objArrayOop(_obj)->length();

 }

 #endif // ASSERT

 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;

 }