hotspot/src/share/vm/gc_implementation/g1/concurrentZFThread.cpp - platform/libcore - Git at Google

 /*
  * 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));

 }
	/*
	* 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));

	}