Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * Copyright (c) 2001, 2010, 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_implementation/g1/concurrentZFThread.hpp"

 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"

 #include "gc_implementation/g1/heapRegion.hpp"

 #include "memory/space.inline.hpp"

 #include "runtime/mutexLocker.hpp"

 #include "utilities/copy.hpp"

 // ======= 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));

 }