/*

 * 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/_concurrentZFThread.cpp.incl"

// ======= Concurrent Zero-Fill Thread ========

// The CM thread is created when the G1 garbage collector is used

int ConcurrentZFThread::_region_allocs = 0;

int ConcurrentZFThread::_sync_zfs = 0;

int ConcurrentZFThread::_zf_waits = 0;

int ConcurrentZFThread::_regions_filled = 0;

ConcurrentZFThread::ConcurrentZFThread() :

  ConcurrentGCThread()

{

  create_and_start();

}

void ConcurrentZFThread::wait_for_ZF_completed(HeapRegion* hr) {

  assert(ZF_mon->owned_by_self(), "Precondition.");

  note_zf_wait();

  while (hr->zero_fill_state() == HeapRegion::ZeroFilling) {

    ZF_mon->wait(Mutex::_no_safepoint_check_flag);

  }

}

void ConcurrentZFThread::processHeapRegion(HeapRegion* hr) {

  assert(!Universe::heap()->is_gc_active(),

         "This should not happen during GC.");

  assert(hr != NULL, "Precondition");

  // These are unlocked reads, but if this test is successful, then no

  // other thread will attempt this zero filling.  Only a GC thread can

  // modify the ZF state of a region whose state is zero-filling, and this

  // should only happen while the ZF thread is locking out GC.

  if (hr->zero_fill_state() == HeapRegion::ZeroFilling

      && hr->zero_filler() == Thread::current()) {

    assert(hr->top() == hr->bottom(), "better be empty!");

    assert(!hr->isHumongous(), "Only free regions on unclean list.");

    Copy::fill_to_words(hr->bottom(), hr->capacity()/HeapWordSize);

    note_region_filled();

  }

}

void ConcurrentZFThread::run() {

  initialize_in_thread();

  Thread* thr_self = Thread::current();

  _vtime_start = os::elapsedVTime();

  wait_for_universe_init();

  G1CollectedHeap* g1 = G1CollectedHeap::heap();

  _sts.join();

  while (!_should_terminate) {

    _sts.leave();

    {

      MutexLockerEx x(ZF_mon, Mutex::_no_safepoint_check_flag);

      // This local variable will hold a region being zero-filled.  This

      // region will neither be on the unclean or zero-filled lists, and

      // will not be available for allocation; thus, we might have an

      // allocation fail, causing a full GC, because of this, but this is a

      // price we will pay.  (In future, we might want to make the fact

      // that there's a region being zero-filled apparent to the G1 heap,

      // which could then wait for it in this extreme case...)

      HeapRegion* to_fill;

      while (!g1->should_zf()

             || (to_fill = g1->pop_unclean_region_list_locked()) == NULL)

        ZF_mon->wait(Mutex::_no_safepoint_check_flag);

      while (to_fill->zero_fill_state() == HeapRegion::ZeroFilling)

        ZF_mon->wait(Mutex::_no_safepoint_check_flag);

      // So now to_fill is non-NULL and is not ZeroFilling.  It might be

      // Allocated or ZeroFilled.  (The latter could happen if this thread

      // starts the zero-filling of a region, but a GC intervenes and

      // pushes new regions needing on the front of the filling on the

      // front of the list.)

      switch (to_fill->zero_fill_state()) {

      case HeapRegion::Allocated:

        to_fill = NULL;

        break;

      case HeapRegion::NotZeroFilled:

        to_fill->set_zero_fill_in_progress(thr_self);

        ZF_mon->unlock();

        _sts.join();

        processHeapRegion(to_fill);

        _sts.leave();

        ZF_mon->lock_without_safepoint_check();

        if (to_fill->zero_fill_state() == HeapRegion::ZeroFilling

            && to_fill->zero_filler() == thr_self) {

          to_fill->set_zero_fill_complete();

          (void)g1->put_free_region_on_list_locked(to_fill);

        }

        break;

      case HeapRegion::ZeroFilled:

        (void)g1->put_free_region_on_list_locked(to_fill);

        break;

      case HeapRegion::ZeroFilling:

        ShouldNotReachHere();

        break;

      }

    }

    _vtime_accum = (os::elapsedVTime() - _vtime_start);

    _sts.join();

  }

  _sts.leave();

  assert(_should_terminate, "just checking");

  terminate();

}

bool ConcurrentZFThread::offer_yield() {

  if (_sts.should_yield()) {

    _sts.yield("Concurrent ZF");

    return true;

  } else {

    return false;

  }

}

void ConcurrentZFThread::stop() {

  // it is ok to take late safepoints here, if needed

  MutexLockerEx mu(Terminator_lock);

  _should_terminate = true;

  while (!_has_terminated) {

    Terminator_lock->wait();

  }

}

void ConcurrentZFThread::print() const {

  print_on(tty);

}

void ConcurrentZFThread::print_on(outputStream* st) const {

  st->print("\"G1 Concurrent Zero-Fill Thread\" ");

  Thread::print_on(st);

  st->cr();

}

double ConcurrentZFThread::_vtime_accum;

void ConcurrentZFThread::print_summary_info() {

  gclog_or_tty->print("\nConcurrent Zero-Filling:\n");

  gclog_or_tty->print("  Filled %d regions, used %5.2fs.\n",

                      _regions_filled,

                      vtime_accum());

  gclog_or_tty->print("  Of %d region allocs, %d (%5.2f%%) required sync ZF,\n",

                      _region_allocs, _sync_zfs,

                      (_region_allocs > 0 ?

                       (float)_sync_zfs/(float)_region_allocs*100.0 :

                       0.0));

  gclog_or_tty->print("     and %d (%5.2f%%) required a ZF wait.\n",

                      _zf_waits,

                      (_region_allocs > 0 ?

                       (float)_zf_waits/(float)_region_allocs*100.0 :

                       0.0));

}