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

 /*
  * Copyright (c) 2001, 2011, 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/g1CollectedHeap.inline.hpp"
 #include "gc_implementation/g1/satbQueue.hpp"
 #include "memory/allocation.inline.hpp"
 #include "memory/sharedHeap.hpp"
 #include "runtime/mutexLocker.hpp"
 #include "runtime/thread.hpp"
 #include "runtime/vmThread.hpp"

 // This method removes entries from an SATB buffer that will not be
 // useful to the concurrent marking threads. An entry is removed if it
 // satisfies one of the following conditions:
 //
 // * it points to an object outside the G1 heap (G1's concurrent
 //     marking only visits objects inside the G1 heap),
 // * it points to an object that has been allocated since marking
 //     started (according to SATB those objects do not need to be
 //     visited during marking), or
 // * it points to an object that has already been marked (no need to
 //     process it again).
 //
 // The rest of the entries will be retained and are compacted towards
 // the top of the buffer. If with this filtering we clear a large
 // enough chunk of the buffer we can re-use it (instead of enqueueing
 // it) and we can just allow the mutator to carry on executing.

 bool ObjPtrQueue::should_enqueue_buffer() {
   assert(_lock == NULL || _lock->owned_by_self(),
          "we should have taken the lock before calling this");

   // A value of 0 means "don't filter SATB buffers".
   if (G1SATBBufferEnqueueingThresholdPercent == 0) {
     return true;
   }

   G1CollectedHeap* g1h = G1CollectedHeap::heap();

   // This method should only be called if there is a non-NULL buffer
   // that is full.
   assert(_index == 0, "pre-condition");
   assert(_buf != NULL, "pre-condition");

   void** buf = _buf;
   size_t sz = _sz;

   // Used for sanity checking at the end of the loop.
   debug_only(size_t entries = 0; size_t retained = 0;)

   size_t i = sz;
   size_t new_index = sz;

   // Given that we are expecting _index == 0, we could have changed
   // the loop condition to (i > 0). But we are using _index for
   // generality.
   while (i > _index) {
     assert(i > 0, "we should have at least one more entry to process");
     i -= oopSize;
     debug_only(entries += 1;)
     oop* p = (oop*) &buf[byte_index_to_index((int) i)];
     oop obj = *p;
     // NULL the entry so that unused parts of the buffer contain NULLs
     // at the end. If we are going to retain it we will copy it to its
     // final place. If we have retained all entries we have visited so
     // far, we'll just end up copying it to the same place.
     *p = NULL;

     bool retain = g1h->is_obj_ill(obj);
     if (retain) {
       assert(new_index > 0, "we should not have already filled up the buffer");
       new_index -= oopSize;
       assert(new_index >= i,
              "new_index should never be below i, as we alwaysr compact 'up'");
       oop* new_p = (oop*) &buf[byte_index_to_index((int) new_index)];
       assert(new_p >= p, "the destination location should never be below "
              "the source as we always compact 'up'");
       assert(*new_p == NULL,
              "we should have already cleared the destination location");
       *new_p = obj;
       debug_only(retained += 1;)
     }
   }
   size_t entries_calc = (sz - _index) / oopSize;
   assert(entries == entries_calc, "the number of entries we counted "
          "should match the number of entries we calculated");
   size_t retained_calc = (sz - new_index) / oopSize;
   assert(retained == retained_calc, "the number of retained entries we counted "
          "should match the number of retained entries we calculated");
   size_t perc = retained_calc * 100 / entries_calc;
   bool should_enqueue = perc > (size_t) G1SATBBufferEnqueueingThresholdPercent;
   _index = new_index;

   return should_enqueue;
 }

 void ObjPtrQueue::apply_closure(ObjectClosure* cl) {
   if (_buf != NULL) {
     apply_closure_to_buffer(cl, _buf, _index, _sz);
     _index = _sz;
   }
 }

 void ObjPtrQueue::apply_closure_to_buffer(ObjectClosure* cl,
                                           void** buf, size_t index, size_t sz) {
   if (cl == NULL) return;
   for (size_t i = index; i < sz; i += oopSize) {
     oop obj = (oop)buf[byte_index_to_index((int)i)];
     // There can be NULL entries because of destructors.
     if (obj != NULL) {
       cl->do_object(obj);
     }
   }
 }

 #ifdef ASSERT
 void ObjPtrQueue::verify_oops_in_buffer() {
   if (_buf == NULL) return;
   for (size_t i = _index; i < _sz; i += oopSize) {
     oop obj = (oop)_buf[byte_index_to_index((int)i)];
     assert(obj != NULL && obj->is_oop(true /* ignore mark word */),
            "Not an oop");
   }
 }
 #endif

 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
 #endif // _MSC_VER


 SATBMarkQueueSet::SATBMarkQueueSet() :
   PtrQueueSet(),
   _closure(NULL), _par_closures(NULL),
   _shared_satb_queue(this, true /*perm*/)
 {}

 void SATBMarkQueueSet::initialize(Monitor* cbl_mon, Mutex* fl_lock,
                                   int process_completed_threshold,
                                   Mutex* lock) {
   PtrQueueSet::initialize(cbl_mon, fl_lock, process_completed_threshold, -1);
   _shared_satb_queue.set_lock(lock);
   if (ParallelGCThreads > 0) {
     _par_closures = NEW_C_HEAP_ARRAY(ObjectClosure*, ParallelGCThreads);
   }
 }


 void SATBMarkQueueSet::handle_zero_index_for_thread(JavaThread* t) {
   DEBUG_ONLY(t->satb_mark_queue().verify_oops_in_buffer();)
   t->satb_mark_queue().handle_zero_index();
 }

 #ifdef ASSERT
 void SATBMarkQueueSet::dump_active_values(JavaThread* first,
                                           bool expected_active) {
   gclog_or_tty->print_cr("SATB queue active values for Java Threads");
   gclog_or_tty->print_cr(" SATB queue set: active is %s",
                          (is_active()) ? "TRUE" : "FALSE");
   gclog_or_tty->print_cr(" expected_active is %s",
                          (expected_active) ? "TRUE" : "FALSE");
   for (JavaThread* t = first; t; t = t->next()) {
     bool active = t->satb_mark_queue().is_active();
     gclog_or_tty->print_cr("  thread %s, active is %s",
                            t->name(), (active) ? "TRUE" : "FALSE");
   }
 }
 #endif // ASSERT

 void SATBMarkQueueSet::set_active_all_threads(bool b,
                                               bool expected_active) {
   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
   JavaThread* first = Threads::first();

 #ifdef ASSERT
   if (_all_active != expected_active) {
     dump_active_values(first, expected_active);

     // I leave this here as a guarantee, instead of an assert, so
     // that it will still be compiled in if we choose to uncomment
     // the #ifdef ASSERT in a product build. The whole block is
     // within an #ifdef ASSERT so the guarantee will not be compiled
     // in a product build anyway.
     guarantee(false,
               "SATB queue set has an unexpected active value");
   }
 #endif // ASSERT
   _all_active = b;

   for (JavaThread* t = first; t; t = t->next()) {
 #ifdef ASSERT
     bool active = t->satb_mark_queue().is_active();
     if (active != expected_active) {
       dump_active_values(first, expected_active);

       // I leave this here as a guarantee, instead of an assert, so
       // that it will still be compiled in if we choose to uncomment
       // the #ifdef ASSERT in a product build. The whole block is
       // within an #ifdef ASSERT so the guarantee will not be compiled
       // in a product build anyway.
       guarantee(false,
                 "thread has an unexpected active value in its SATB queue");
     }
 #endif // ASSERT
     t->satb_mark_queue().set_active(b);
   }
 }

 void SATBMarkQueueSet::set_closure(ObjectClosure* closure) {
   _closure = closure;
 }

 void SATBMarkQueueSet::set_par_closure(int i, ObjectClosure* par_closure) {
   assert(ParallelGCThreads > 0 && _par_closures != NULL, "Precondition");
   _par_closures[i] = par_closure;
 }

 void SATBMarkQueueSet::iterate_closure_all_threads() {
   for(JavaThread* t = Threads::first(); t; t = t->next()) {
     t->satb_mark_queue().apply_closure(_closure);
   }
   shared_satb_queue()->apply_closure(_closure);
 }

 void SATBMarkQueueSet::par_iterate_closure_all_threads(int worker) {
   SharedHeap* sh = SharedHeap::heap();
   int parity = sh->strong_roots_parity();

   for(JavaThread* t = Threads::first(); t; t = t->next()) {
     if (t->claim_oops_do(true, parity)) {
       t->satb_mark_queue().apply_closure(_par_closures[worker]);
     }
   }

   // We also need to claim the VMThread so that its parity is updated
   // otherwise the next call to Thread::possibly_parallel_oops_do inside
   // a StrongRootsScope might skip the VMThread because it has a stale
   // parity that matches the parity set by the StrongRootsScope
   //
   // Whichever worker succeeds in claiming the VMThread gets to do
   // the shared queue.

   VMThread* vmt = VMThread::vm_thread();
   if (vmt->claim_oops_do(true, parity)) {
     shared_satb_queue()->apply_closure(_par_closures[worker]);
   }
 }

 bool SATBMarkQueueSet::apply_closure_to_completed_buffer_work(bool par,
                                                               int worker) {
   BufferNode* nd = NULL;
   {
     MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
     if (_completed_buffers_head != NULL) {
       nd = _completed_buffers_head;
       _completed_buffers_head = nd->next();
       if (_completed_buffers_head == NULL) _completed_buffers_tail = NULL;
       _n_completed_buffers--;
       if (_n_completed_buffers == 0) _process_completed = false;
     }
   }
   ObjectClosure* cl = (par ? _par_closures[worker] : _closure);
   if (nd != NULL) {
     void **buf = BufferNode::make_buffer_from_node(nd);
     ObjPtrQueue::apply_closure_to_buffer(cl, buf, 0, _sz);
     deallocate_buffer(buf);
     return true;
   } else {
     return false;
   }
 }

 void SATBMarkQueueSet::abandon_partial_marking() {
   BufferNode* buffers_to_delete = NULL;
   {
     MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
     while (_completed_buffers_head != NULL) {
       BufferNode* nd = _completed_buffers_head;
       _completed_buffers_head = nd->next();
       nd->set_next(buffers_to_delete);
       buffers_to_delete = nd;
     }
     _completed_buffers_tail = NULL;
     _n_completed_buffers = 0;
     DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked());
   }
   while (buffers_to_delete != NULL) {
     BufferNode* nd = buffers_to_delete;
     buffers_to_delete = nd->next();
     deallocate_buffer(BufferNode::make_buffer_from_node(nd));
   }
   assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
   // So we can safely manipulate these queues.
   for (JavaThread* t = Threads::first(); t; t = t->next()) {
     t->satb_mark_queue().reset();
   }
   shared_satb_queue()->reset();
 }
	/*
	* Copyright (c) 2001, 2011, 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/g1CollectedHeap.inline.hpp"
	#include "gc_implementation/g1/satbQueue.hpp"
	#include "memory/allocation.inline.hpp"
	#include "memory/sharedHeap.hpp"
	#include "runtime/mutexLocker.hpp"
	#include "runtime/thread.hpp"
	#include "runtime/vmThread.hpp"

	// This method removes entries from an SATB buffer that will not be
	// useful to the concurrent marking threads. An entry is removed if it
	// satisfies one of the following conditions:
	//
	// * it points to an object outside the G1 heap (G1's concurrent
	// marking only visits objects inside the G1 heap),
	// * it points to an object that has been allocated since marking
	// started (according to SATB those objects do not need to be
	// visited during marking), or
	// * it points to an object that has already been marked (no need to
	// process it again).
	//
	// The rest of the entries will be retained and are compacted towards
	// the top of the buffer. If with this filtering we clear a large
	// enough chunk of the buffer we can re-use it (instead of enqueueing
	// it) and we can just allow the mutator to carry on executing.

	bool ObjPtrQueue::should_enqueue_buffer() {
	assert(_lock == NULL \|\| _lock->owned_by_self(),
	"we should have taken the lock before calling this");

	// A value of 0 means "don't filter SATB buffers".
	if (G1SATBBufferEnqueueingThresholdPercent == 0) {
	return true;
	}

	G1CollectedHeap* g1h = G1CollectedHeap::heap();

	// This method should only be called if there is a non-NULL buffer
	// that is full.
	assert(_index == 0, "pre-condition");
	assert(_buf != NULL, "pre-condition");

	void** buf = _buf;
	size_t sz = _sz;

	// Used for sanity checking at the end of the loop.
	debug_only(size_t entries = 0; size_t retained = 0;)

	size_t i = sz;
	size_t new_index = sz;

	// Given that we are expecting _index == 0, we could have changed
	// the loop condition to (i > 0). But we are using _index for
	// generality.
	while (i > _index) {
	assert(i > 0, "we should have at least one more entry to process");
	i -= oopSize;
	debug_only(entries += 1;)
	oop* p = (oop*) &buf[byte_index_to_index((int) i)];
	oop obj = *p;
	// NULL the entry so that unused parts of the buffer contain NULLs
	// at the end. If we are going to retain it we will copy it to its
	// final place. If we have retained all entries we have visited so
	// far, we'll just end up copying it to the same place.
	*p = NULL;

	bool retain = g1h->is_obj_ill(obj);
	if (retain) {
	assert(new_index > 0, "we should not have already filled up the buffer");
	new_index -= oopSize;
	assert(new_index >= i,
	"new_index should never be below i, as we alwaysr compact 'up'");
	oop* new_p = (oop*) &buf[byte_index_to_index((int) new_index)];
	assert(new_p >= p, "the destination location should never be below "
	"the source as we always compact 'up'");
	assert(*new_p == NULL,
	"we should have already cleared the destination location");
	*new_p = obj;
	debug_only(retained += 1;)
	}
	}
	size_t entries_calc = (sz - _index) / oopSize;
	assert(entries == entries_calc, "the number of entries we counted "
	"should match the number of entries we calculated");
	size_t retained_calc = (sz - new_index) / oopSize;
	assert(retained == retained_calc, "the number of retained entries we counted "
	"should match the number of retained entries we calculated");
	size_t perc = retained_calc * 100 / entries_calc;
	bool should_enqueue = perc > (size_t) G1SATBBufferEnqueueingThresholdPercent;
	_index = new_index;

	return should_enqueue;
	}

	void ObjPtrQueue::apply_closure(ObjectClosure* cl) {
	if (_buf != NULL) {
	apply_closure_to_buffer(cl, _buf, _index, _sz);
	_index = _sz;
	}
	}

	void ObjPtrQueue::apply_closure_to_buffer(ObjectClosure* cl,
	void** buf, size_t index, size_t sz) {
	if (cl == NULL) return;
	for (size_t i = index; i < sz; i += oopSize) {
	oop obj = (oop)buf[byte_index_to_index((int)i)];
	// There can be NULL entries because of destructors.
	if (obj != NULL) {
	cl->do_object(obj);
	}
	}
	}

	#ifdef ASSERT
	void ObjPtrQueue::verify_oops_in_buffer() {
	if (_buf == NULL) return;
	for (size_t i = _index; i < _sz; i += oopSize) {
	oop obj = (oop)_buf[byte_index_to_index((int)i)];
	assert(obj != NULL && obj->is_oop(true /* ignore mark word */),
	"Not an oop");
	}
	}
	#endif

	#ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
	#pragma warning( disable:4355 ) // 'this' : used in base member initializer list
	#endif // _MSC_VER


	SATBMarkQueueSet::SATBMarkQueueSet() :
	PtrQueueSet(),
	_closure(NULL), _par_closures(NULL),
	_shared_satb_queue(this, true /perm/)
	{}

	void SATBMarkQueueSet::initialize(Monitor* cbl_mon, Mutex* fl_lock,
	int process_completed_threshold,
	Mutex* lock) {
	PtrQueueSet::initialize(cbl_mon, fl_lock, process_completed_threshold, -1);
	_shared_satb_queue.set_lock(lock);
	if (ParallelGCThreads > 0) {
	_par_closures = NEW_C_HEAP_ARRAY(ObjectClosure*, ParallelGCThreads);
	}
	}


	void SATBMarkQueueSet::handle_zero_index_for_thread(JavaThread* t) {
	DEBUG_ONLY(t->satb_mark_queue().verify_oops_in_buffer();)
	t->satb_mark_queue().handle_zero_index();
	}

	#ifdef ASSERT
	void SATBMarkQueueSet::dump_active_values(JavaThread* first,
	bool expected_active) {
	gclog_or_tty->print_cr("SATB queue active values for Java Threads");
	gclog_or_tty->print_cr(" SATB queue set: active is %s",
	(is_active()) ? "TRUE" : "FALSE");
	gclog_or_tty->print_cr(" expected_active is %s",
	(expected_active) ? "TRUE" : "FALSE");
	for (JavaThread* t = first; t; t = t->next()) {
	bool active = t->satb_mark_queue().is_active();
	gclog_or_tty->print_cr(" thread %s, active is %s",
	t->name(), (active) ? "TRUE" : "FALSE");
	}
	}
	#endif // ASSERT

	void SATBMarkQueueSet::set_active_all_threads(bool b,
	bool expected_active) {
	assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
	JavaThread* first = Threads::first();

	#ifdef ASSERT
	if (_all_active != expected_active) {
	dump_active_values(first, expected_active);

	// I leave this here as a guarantee, instead of an assert, so
	// that it will still be compiled in if we choose to uncomment
	// the #ifdef ASSERT in a product build. The whole block is
	// within an #ifdef ASSERT so the guarantee will not be compiled
	// in a product build anyway.
	guarantee(false,
	"SATB queue set has an unexpected active value");
	}
	#endif // ASSERT
	_all_active = b;

	for (JavaThread* t = first; t; t = t->next()) {
	#ifdef ASSERT
	bool active = t->satb_mark_queue().is_active();
	if (active != expected_active) {
	dump_active_values(first, expected_active);

	// I leave this here as a guarantee, instead of an assert, so
	// that it will still be compiled in if we choose to uncomment
	// the #ifdef ASSERT in a product build. The whole block is
	// within an #ifdef ASSERT so the guarantee will not be compiled
	// in a product build anyway.
	guarantee(false,
	"thread has an unexpected active value in its SATB queue");
	}
	#endif // ASSERT
	t->satb_mark_queue().set_active(b);
	}
	}

	void SATBMarkQueueSet::set_closure(ObjectClosure* closure) {
	_closure = closure;
	}

	void SATBMarkQueueSet::set_par_closure(int i, ObjectClosure* par_closure) {
	assert(ParallelGCThreads > 0 && _par_closures != NULL, "Precondition");
	_par_closures[i] = par_closure;
	}

	void SATBMarkQueueSet::iterate_closure_all_threads() {
	for(JavaThread* t = Threads::first(); t; t = t->next()) {
	t->satb_mark_queue().apply_closure(_closure);
	}
	shared_satb_queue()->apply_closure(_closure);
	}

	void SATBMarkQueueSet::par_iterate_closure_all_threads(int worker) {
	SharedHeap* sh = SharedHeap::heap();
	int parity = sh->strong_roots_parity();

	for(JavaThread* t = Threads::first(); t; t = t->next()) {
	if (t->claim_oops_do(true, parity)) {
	t->satb_mark_queue().apply_closure(_par_closures[worker]);
	}
	}

	// We also need to claim the VMThread so that its parity is updated
	// otherwise the next call to Thread::possibly_parallel_oops_do inside
	// a StrongRootsScope might skip the VMThread because it has a stale
	// parity that matches the parity set by the StrongRootsScope
	//
	// Whichever worker succeeds in claiming the VMThread gets to do
	// the shared queue.

	VMThread* vmt = VMThread::vm_thread();
	if (vmt->claim_oops_do(true, parity)) {
	shared_satb_queue()->apply_closure(_par_closures[worker]);
	}
	}

	bool SATBMarkQueueSet::apply_closure_to_completed_buffer_work(bool par,
	int worker) {
	BufferNode* nd = NULL;
	{
	MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
	if (_completed_buffers_head != NULL) {
	nd = _completed_buffers_head;
	_completed_buffers_head = nd->next();
	if (_completed_buffers_head == NULL) _completed_buffers_tail = NULL;
	_n_completed_buffers--;
	if (_n_completed_buffers == 0) _process_completed = false;
	}
	}
	ObjectClosure* cl = (par ? _par_closures[worker] : _closure);
	if (nd != NULL) {
	void **buf = BufferNode::make_buffer_from_node(nd);
	ObjPtrQueue::apply_closure_to_buffer(cl, buf, 0, _sz);
	deallocate_buffer(buf);
	return true;
	} else {
	return false;
	}
	}

	void SATBMarkQueueSet::abandon_partial_marking() {
	BufferNode* buffers_to_delete = NULL;
	{
	MutexLockerEx x(_cbl_mon, Mutex::_no_safepoint_check_flag);
	while (_completed_buffers_head != NULL) {
	BufferNode* nd = _completed_buffers_head;
	_completed_buffers_head = nd->next();
	nd->set_next(buffers_to_delete);
	buffers_to_delete = nd;
	}
	_completed_buffers_tail = NULL;
	_n_completed_buffers = 0;
	DEBUG_ONLY(assert_completed_buffer_list_len_correct_locked());
	}
	while (buffers_to_delete != NULL) {
	BufferNode* nd = buffers_to_delete;
	buffers_to_delete = nd->next();
	deallocate_buffer(BufferNode::make_buffer_from_node(nd));
	}
	assert(SafepointSynchronize::is_at_safepoint(), "Must be at safepoint.");
	// So we can safely manipulate these queues.
	for (JavaThread* t = Threads::first(); t; t = t->next()) {
	t->satb_mark_queue().reset();
	}
	shared_satb_queue()->reset();
	}