hotspot/src/share/vm/gc_implementation/g1/g1EvacFailure.hpp - edge/openjdk - Git at Google

 /*
  * Copyright (c) 2012, 2013, 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.
  *
  */

 #ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1EVACFAILURE_HPP
 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1EVACFAILURE_HPP

 #include "gc_implementation/g1/concurrentMark.inline.hpp"
 #include "gc_implementation/g1/dirtyCardQueue.hpp"
 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
 #include "gc_implementation/g1/g1_globals.hpp"
 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
 #include "gc_implementation/g1/heapRegion.hpp"
 #include "gc_implementation/g1/heapRegionRemSet.hpp"
 #include "utilities/workgroup.hpp"

 // Closures and tasks associated with any self-forwarding pointers
 // installed as a result of an evacuation failure.

 class UpdateRSetDeferred : public OopsInHeapRegionClosure {
 private:
   G1CollectedHeap* _g1;
   DirtyCardQueue *_dcq;
   G1SATBCardTableModRefBS* _ct_bs;

 public:
   UpdateRSetDeferred(G1CollectedHeap* g1, DirtyCardQueue* dcq) :
     _g1(g1), _ct_bs(_g1->g1_barrier_set()), _dcq(dcq) {}

   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
   virtual void do_oop(      oop* p) { do_oop_work(p); }
   template <class T> void do_oop_work(T* p) {
     assert(_from->is_in_reserved(p), "paranoia");
     if (!_from->is_in_reserved(oopDesc::load_decode_heap_oop(p)) &&
         !_from->is_survivor()) {
       size_t card_index = _ct_bs->index_for(p);
       if (_ct_bs->mark_card_deferred(card_index)) {
         _dcq->enqueue((jbyte*)_ct_bs->byte_for_index(card_index));
       }
     }
   }
 };

 class RemoveSelfForwardPtrObjClosure: public ObjectClosure {
 private:
   G1CollectedHeap* _g1;
   ConcurrentMark* _cm;
   HeapRegion* _hr;
   size_t _marked_bytes;
   OopsInHeapRegionClosure *_update_rset_cl;
   bool _during_initial_mark;
   bool _during_conc_mark;
   uint _worker_id;
   HeapWord* _end_of_last_gap;
   HeapWord* _last_gap_threshold;
   HeapWord* _last_obj_threshold;

 public:
   RemoveSelfForwardPtrObjClosure(G1CollectedHeap* g1, ConcurrentMark* cm,
                                  HeapRegion* hr,
                                  OopsInHeapRegionClosure* update_rset_cl,
                                  bool during_initial_mark,
                                  bool during_conc_mark,
                                  uint worker_id) :
     _g1(g1), _cm(cm), _hr(hr), _marked_bytes(0),
     _update_rset_cl(update_rset_cl),
     _during_initial_mark(during_initial_mark),
     _during_conc_mark(during_conc_mark),
     _worker_id(worker_id),
     _end_of_last_gap(hr->bottom()),
     _last_gap_threshold(hr->bottom()),
     _last_obj_threshold(hr->bottom()) { }

   size_t marked_bytes() { return _marked_bytes; }

   // <original comment>
   // The original idea here was to coalesce evacuated and dead objects.
   // However that caused complications with the block offset table (BOT).
   // In particular if there were two TLABs, one of them partially refined.
   // |----- TLAB_1--------|----TLAB_2-~~~(partially refined part)~~~|
   // The BOT entries of the unrefined part of TLAB_2 point to the start
   // of TLAB_2. If the last object of the TLAB_1 and the first object
   // of TLAB_2 are coalesced, then the cards of the unrefined part
   // would point into middle of the filler object.
   // The current approach is to not coalesce and leave the BOT contents intact.
   // </original comment>
   //
   // We now reset the BOT when we start the object iteration over the
   // region and refine its entries for every object we come across. So
   // the above comment is not really relevant and we should be able
   // to coalesce dead objects if we want to.
   void do_object(oop obj) {
     HeapWord* obj_addr = (HeapWord*) obj;
     assert(_hr->is_in(obj_addr), "sanity");
     size_t obj_size = obj->size();
     HeapWord* obj_end = obj_addr + obj_size;

     if (_end_of_last_gap != obj_addr) {
       // there was a gap before obj_addr
       _last_gap_threshold = _hr->cross_threshold(_end_of_last_gap, obj_addr);
     }

     if (obj->is_forwarded() && obj->forwardee() == obj) {
       // The object failed to move.

       // We consider all objects that we find self-forwarded to be
       // live. What we'll do is that we'll update the prev marking
       // info so that they are all under PTAMS and explicitly marked.
       if (!_cm->isPrevMarked(obj)) {
         _cm->markPrev(obj);
       }
       if (_during_initial_mark) {
         // For the next marking info we'll only mark the
         // self-forwarded objects explicitly if we are during
         // initial-mark (since, normally, we only mark objects pointed
         // to by roots if we succeed in copying them). By marking all
         // self-forwarded objects we ensure that we mark any that are
         // still pointed to be roots. During concurrent marking, and
         // after initial-mark, we don't need to mark any objects
         // explicitly and all objects in the CSet are considered
         // (implicitly) live. So, we won't mark them explicitly and
         // we'll leave them over NTAMS.
         _cm->grayRoot(obj, obj_size, _worker_id, _hr);
       }
       _marked_bytes += (obj_size * HeapWordSize);
       obj->set_mark(markOopDesc::prototype());

       // While we were processing RSet buffers during the collection,
       // we actually didn't scan any cards on the collection set,
       // since we didn't want to update remembered sets with entries
       // that point into the collection set, given that live objects
       // from the collection set are about to move and such entries
       // will be stale very soon.
       // This change also dealt with a reliability issue which
       // involved scanning a card in the collection set and coming
       // across an array that was being chunked and looking malformed.
       // The problem is that, if evacuation fails, we might have
       // remembered set entries missing given that we skipped cards on
       // the collection set. So, we'll recreate such entries now.
       obj->oop_iterate(_update_rset_cl);
     } else {

       // The object has been either evacuated or is dead. Fill it with a
       // dummy object.
       MemRegion mr(obj_addr, obj_size);
       CollectedHeap::fill_with_object(mr);

       // must nuke all dead objects which we skipped when iterating over the region
       _cm->clearRangePrevBitmap(MemRegion(_end_of_last_gap, obj_end));
     }
     _end_of_last_gap = obj_end;
     _last_obj_threshold = _hr->cross_threshold(obj_addr, obj_end);
   }
 };

 class RemoveSelfForwardPtrHRClosure: public HeapRegionClosure {
   G1CollectedHeap* _g1h;
   ConcurrentMark* _cm;
   uint _worker_id;

   DirtyCardQueue _dcq;
   UpdateRSetDeferred _update_rset_cl;

 public:
   RemoveSelfForwardPtrHRClosure(G1CollectedHeap* g1h,
                                 uint worker_id) :
     _g1h(g1h), _dcq(&g1h->dirty_card_queue_set()), _update_rset_cl(g1h, &_dcq),
     _worker_id(worker_id), _cm(_g1h->concurrent_mark()) {
     }

   bool doHeapRegion(HeapRegion *hr) {
     bool during_initial_mark = _g1h->g1_policy()->during_initial_mark_pause();
     bool during_conc_mark = _g1h->mark_in_progress();

     assert(!hr->isHumongous(), "sanity");
     assert(hr->in_collection_set(), "bad CS");

     if (hr->claimHeapRegion(HeapRegion::ParEvacFailureClaimValue)) {
       if (hr->evacuation_failed()) {
         RemoveSelfForwardPtrObjClosure rspc(_g1h, _cm, hr, &_update_rset_cl,
                                             during_initial_mark,
                                             during_conc_mark,
                                             _worker_id);

         hr->note_self_forwarding_removal_start(during_initial_mark,
                                                during_conc_mark);
         _g1h->check_bitmaps("Self-Forwarding Ptr Removal", hr);

         // In the common case (i.e. when there is no evacuation
         // failure) we make sure that the following is done when
         // the region is freed so that it is "ready-to-go" when it's
         // re-allocated. However, when evacuation failure happens, a
         // region will remain in the heap and might ultimately be added
         // to a CSet in the future. So we have to be careful here and
         // make sure the region's RSet is ready for parallel iteration
         // whenever this might be required in the future.
         hr->rem_set()->reset_for_par_iteration();
         hr->reset_bot();
         _update_rset_cl.set_region(hr);
         hr->object_iterate(&rspc);

         hr->rem_set()->clean_strong_code_roots(hr);

         hr->note_self_forwarding_removal_end(during_initial_mark,
                                              during_conc_mark,
                                              rspc.marked_bytes());
       }
     }
     return false;
   }
 };

 class G1ParRemoveSelfForwardPtrsTask: public AbstractGangTask {
 protected:
   G1CollectedHeap* _g1h;

 public:
   G1ParRemoveSelfForwardPtrsTask(G1CollectedHeap* g1h) :
     AbstractGangTask("G1 Remove Self-forwarding Pointers"),
     _g1h(g1h) { }

   void work(uint worker_id) {
     RemoveSelfForwardPtrHRClosure rsfp_cl(_g1h, worker_id);

     HeapRegion* hr = _g1h->start_cset_region_for_worker(worker_id);
     _g1h->collection_set_iterate_from(hr, &rsfp_cl);
   }
 };

 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1EVACFAILURE_HPP
	/*
	* Copyright (c) 2012, 2013, 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.
	*
	*/

	#ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1EVACFAILURE_HPP
	#define SHARE_VM_GC_IMPLEMENTATION_G1_G1EVACFAILURE_HPP

	#include "gc_implementation/g1/concurrentMark.inline.hpp"
	#include "gc_implementation/g1/dirtyCardQueue.hpp"
	#include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
	#include "gc_implementation/g1/g1_globals.hpp"
	#include "gc_implementation/g1/g1OopClosures.inline.hpp"
	#include "gc_implementation/g1/heapRegion.hpp"
	#include "gc_implementation/g1/heapRegionRemSet.hpp"
	#include "utilities/workgroup.hpp"

	// Closures and tasks associated with any self-forwarding pointers
	// installed as a result of an evacuation failure.

	class UpdateRSetDeferred : public OopsInHeapRegionClosure {
	private:
	G1CollectedHeap* _g1;
	DirtyCardQueue *_dcq;
	G1SATBCardTableModRefBS* _ct_bs;

	public:
	UpdateRSetDeferred(G1CollectedHeap* g1, DirtyCardQueue* dcq) :
	_g1(g1), _ct_bs(_g1->g1_barrier_set()), _dcq(dcq) {}

	virtual void do_oop(narrowOop* p) { do_oop_work(p); }
	virtual void do_oop( oop* p) { do_oop_work(p); }
	template <class T> void do_oop_work(T* p) {
	assert(_from->is_in_reserved(p), "paranoia");
	if (!_from->is_in_reserved(oopDesc::load_decode_heap_oop(p)) &&
	!_from->is_survivor()) {
	size_t card_index = _ct_bs->index_for(p);
	if (_ct_bs->mark_card_deferred(card_index)) {
	_dcq->enqueue((jbyte*)_ct_bs->byte_for_index(card_index));
	}
	}
	}
	};

	class RemoveSelfForwardPtrObjClosure: public ObjectClosure {
	private:
	G1CollectedHeap* _g1;
	ConcurrentMark* _cm;
	HeapRegion* _hr;
	size_t _marked_bytes;
	OopsInHeapRegionClosure *_update_rset_cl;
	bool _during_initial_mark;
	bool _during_conc_mark;
	uint _worker_id;
	HeapWord* _end_of_last_gap;
	HeapWord* _last_gap_threshold;
	HeapWord* _last_obj_threshold;

	public:
	RemoveSelfForwardPtrObjClosure(G1CollectedHeap* g1, ConcurrentMark* cm,
	HeapRegion* hr,
	OopsInHeapRegionClosure* update_rset_cl,
	bool during_initial_mark,
	bool during_conc_mark,
	uint worker_id) :
	_g1(g1), _cm(cm), _hr(hr), _marked_bytes(0),
	_update_rset_cl(update_rset_cl),
	_during_initial_mark(during_initial_mark),
	_during_conc_mark(during_conc_mark),
	_worker_id(worker_id),
	_end_of_last_gap(hr->bottom()),
	_last_gap_threshold(hr->bottom()),
	_last_obj_threshold(hr->bottom()) { }

	size_t marked_bytes() { return _marked_bytes; }

	// <original comment>
	// The original idea here was to coalesce evacuated and dead objects.
	// However that caused complications with the block offset table (BOT).
	// In particular if there were two TLABs, one of them partially refined.
	// \|----- TLAB_1--------\|----TLAB_2-~~~(partially refined part)~~~\|
	// The BOT entries of the unrefined part of TLAB_2 point to the start
	// of TLAB_2. If the last object of the TLAB_1 and the first object
	// of TLAB_2 are coalesced, then the cards of the unrefined part
	// would point into middle of the filler object.
	// The current approach is to not coalesce and leave the BOT contents intact.
	// </original comment>
	//
	// We now reset the BOT when we start the object iteration over the
	// region and refine its entries for every object we come across. So
	// the above comment is not really relevant and we should be able
	// to coalesce dead objects if we want to.
	void do_object(oop obj) {
	HeapWord* obj_addr = (HeapWord*) obj;
	assert(_hr->is_in(obj_addr), "sanity");
	size_t obj_size = obj->size();
	HeapWord* obj_end = obj_addr + obj_size;

	if (_end_of_last_gap != obj_addr) {
	// there was a gap before obj_addr
	_last_gap_threshold = _hr->cross_threshold(_end_of_last_gap, obj_addr);
	}

	if (obj->is_forwarded() && obj->forwardee() == obj) {
	// The object failed to move.

	// We consider all objects that we find self-forwarded to be
	// live. What we'll do is that we'll update the prev marking
	// info so that they are all under PTAMS and explicitly marked.
	if (!_cm->isPrevMarked(obj)) {
	_cm->markPrev(obj);
	}
	if (_during_initial_mark) {
	// For the next marking info we'll only mark the
	// self-forwarded objects explicitly if we are during
	// initial-mark (since, normally, we only mark objects pointed
	// to by roots if we succeed in copying them). By marking all
	// self-forwarded objects we ensure that we mark any that are
	// still pointed to be roots. During concurrent marking, and
	// after initial-mark, we don't need to mark any objects
	// explicitly and all objects in the CSet are considered
	// (implicitly) live. So, we won't mark them explicitly and
	// we'll leave them over NTAMS.
	_cm->grayRoot(obj, obj_size, _worker_id, _hr);
	}
	_marked_bytes += (obj_size * HeapWordSize);
	obj->set_mark(markOopDesc::prototype());

	// While we were processing RSet buffers during the collection,
	// we actually didn't scan any cards on the collection set,
	// since we didn't want to update remembered sets with entries
	// that point into the collection set, given that live objects
	// from the collection set are about to move and such entries
	// will be stale very soon.
	// This change also dealt with a reliability issue which
	// involved scanning a card in the collection set and coming
	// across an array that was being chunked and looking malformed.
	// The problem is that, if evacuation fails, we might have
	// remembered set entries missing given that we skipped cards on
	// the collection set. So, we'll recreate such entries now.
	obj->oop_iterate(_update_rset_cl);
	} else {

	// The object has been either evacuated or is dead. Fill it with a
	// dummy object.
	MemRegion mr(obj_addr, obj_size);
	CollectedHeap::fill_with_object(mr);

	// must nuke all dead objects which we skipped when iterating over the region
	_cm->clearRangePrevBitmap(MemRegion(_end_of_last_gap, obj_end));
	}
	_end_of_last_gap = obj_end;
	_last_obj_threshold = _hr->cross_threshold(obj_addr, obj_end);
	}
	};

	class RemoveSelfForwardPtrHRClosure: public HeapRegionClosure {
	G1CollectedHeap* _g1h;
	ConcurrentMark* _cm;
	uint _worker_id;

	DirtyCardQueue _dcq;
	UpdateRSetDeferred _update_rset_cl;

	public:
	RemoveSelfForwardPtrHRClosure(G1CollectedHeap* g1h,
	uint worker_id) :
	_g1h(g1h), _dcq(&g1h->dirty_card_queue_set()), _update_rset_cl(g1h, &_dcq),
	_worker_id(worker_id), _cm(_g1h->concurrent_mark()) {
	}

	bool doHeapRegion(HeapRegion *hr) {
	bool during_initial_mark = _g1h->g1_policy()->during_initial_mark_pause();
	bool during_conc_mark = _g1h->mark_in_progress();

	assert(!hr->isHumongous(), "sanity");
	assert(hr->in_collection_set(), "bad CS");

	if (hr->claimHeapRegion(HeapRegion::ParEvacFailureClaimValue)) {
	if (hr->evacuation_failed()) {
	RemoveSelfForwardPtrObjClosure rspc(_g1h, _cm, hr, &_update_rset_cl,
	during_initial_mark,
	during_conc_mark,
	_worker_id);

	hr->note_self_forwarding_removal_start(during_initial_mark,
	during_conc_mark);
	_g1h->check_bitmaps("Self-Forwarding Ptr Removal", hr);

	// In the common case (i.e. when there is no evacuation
	// failure) we make sure that the following is done when
	// the region is freed so that it is "ready-to-go" when it's
	// re-allocated. However, when evacuation failure happens, a
	// region will remain in the heap and might ultimately be added
	// to a CSet in the future. So we have to be careful here and
	// make sure the region's RSet is ready for parallel iteration
	// whenever this might be required in the future.
	hr->rem_set()->reset_for_par_iteration();
	hr->reset_bot();
	_update_rset_cl.set_region(hr);
	hr->object_iterate(&rspc);

	hr->rem_set()->clean_strong_code_roots(hr);

	hr->note_self_forwarding_removal_end(during_initial_mark,
	during_conc_mark,
	rspc.marked_bytes());
	}
	}
	return false;
	}
	};

	class G1ParRemoveSelfForwardPtrsTask: public AbstractGangTask {
	protected:
	G1CollectedHeap* _g1h;

	public:
	G1ParRemoveSelfForwardPtrsTask(G1CollectedHeap* g1h) :
	AbstractGangTask("G1 Remove Self-forwarding Pointers"),
	_g1h(g1h) { }

	void work(uint worker_id) {
	RemoveSelfForwardPtrHRClosure rsfp_cl(_g1h, worker_id);

	HeapRegion* hr = _g1h->start_cset_region_for_worker(worker_id);
	_g1h->collection_set_iterate_from(hr, &rsfp_cl);
	}
	};

	#endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1EVACFAILURE_HPP