/*

 * Copyright (c) 2001, 2015, 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/g1/concurrentG1Refine.hpp"

#include "gc/g1/concurrentG1RefineThread.hpp"

#include "gc/g1/g1BlockOffsetTable.inline.hpp"

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

#include "gc/g1/g1CollectorPolicy.hpp"

#include "gc/g1/g1GCPhaseTimes.hpp"

#include "gc/g1/g1HotCardCache.hpp"

#include "gc/g1/g1OopClosures.inline.hpp"

#include "gc/g1/g1RemSet.inline.hpp"

#include "gc/g1/heapRegion.inline.hpp"

#include "gc/g1/heapRegionManager.inline.hpp"

#include "gc/g1/heapRegionRemSet.hpp"

#include "memory/iterator.hpp"

#include "oops/oop.inline.hpp"

#include "utilities/globalDefinitions.hpp"

#include "utilities/intHisto.hpp"

#include "utilities/stack.inline.hpp"

G1RemSet::G1RemSet(G1CollectedHeap* g1, CardTableModRefBS* ct_bs) :

  _g1(g1),

  _conc_refine_cards(0),

  _ct_bs(ct_bs),

  _g1p(_g1->g1_policy()),

  _cg1r(g1->concurrent_g1_refine()),

  _cset_rs_update_cl(NULL),

  _prev_period_summary(),

  _into_cset_dirty_card_queue_set(false)

{

  _cset_rs_update_cl = NEW_C_HEAP_ARRAY(G1ParPushHeapRSClosure*, n_workers(), mtGC);

  for (uint i = 0; i < n_workers(); i++) {

    _cset_rs_update_cl[i] = NULL;

  }

  if (log_is_enabled(Trace, gc, remset)) {

    _prev_period_summary.initialize(this);

  }

  // Initialize the card queue set used to hold cards containing

  // references into the collection set.

  _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code

                                             DirtyCardQ_CBL_mon,

                                             DirtyCardQ_FL_lock,

                                             -1, // never trigger processing

                                             -1, // no limit on length

                                             Shared_DirtyCardQ_lock,

                                             &JavaThread::dirty_card_queue_set());

}

G1RemSet::~G1RemSet() {

  for (uint i = 0; i < n_workers(); i++) {

    assert(_cset_rs_update_cl[i] == NULL, "it should be");

  }

  FREE_C_HEAP_ARRAY(G1ParPushHeapRSClosure*, _cset_rs_update_cl);

}

ScanRSClosure::ScanRSClosure(G1ParPushHeapRSClosure* oc,

                             CodeBlobClosure* code_root_cl,

                             uint worker_i) :

  _oc(oc),

  _code_root_cl(code_root_cl),

  _strong_code_root_scan_time_sec(0.0),

  _cards(0),

  _cards_done(0),

  _worker_i(worker_i),

  _try_claimed(false) {

  _g1h = G1CollectedHeap::heap();

  _bot_shared = _g1h->bot_shared();

  _ct_bs = _g1h->g1_barrier_set();

  _block_size = MAX2<size_t>(G1RSetScanBlockSize, 1);

}

void ScanRSClosure::scanCard(size_t index, HeapRegion *r) {

  // Stack allocate the DirtyCardToOopClosure instance

  HeapRegionDCTOC cl(_g1h, r, _oc,

      CardTableModRefBS::Precise);

  // Set the "from" region in the closure.

  _oc->set_region(r);

  MemRegion card_region(_bot_shared->address_for_index(index), G1BlockOffsetSharedArray::N_words);

  MemRegion pre_gc_allocated(r->bottom(), r->scan_top());

  MemRegion mr = pre_gc_allocated.intersection(card_region);

  if (!mr.is_empty() && !_ct_bs->is_card_claimed(index)) {

    // We make the card as "claimed" lazily (so races are possible

    // but they're benign), which reduces the number of duplicate

    // scans (the rsets of the regions in the cset can intersect).

    _ct_bs->set_card_claimed(index);

    _cards_done++;

    cl.do_MemRegion(mr);

  }

}

void ScanRSClosure::scan_strong_code_roots(HeapRegion* r) {

  double scan_start = os::elapsedTime();

  r->strong_code_roots_do(_code_root_cl);

  _strong_code_root_scan_time_sec += (os::elapsedTime() - scan_start);

}

bool ScanRSClosure::doHeapRegion(HeapRegion* r) {

  assert(r->in_collection_set(), "should only be called on elements of CS.");

  HeapRegionRemSet* hrrs = r->rem_set();

  if (hrrs->iter_is_complete()) return false; // All done.

  if (!_try_claimed && !hrrs->claim_iter()) return false;

  // If we ever free the collection set concurrently, we should also

  // clear the card table concurrently therefore we won't need to

  // add regions of the collection set to the dirty cards region.

  _g1h->push_dirty_cards_region(r);

  // If we didn't return above, then

  //   _try_claimed || r->claim_iter()

  // is true: either we're supposed to work on claimed-but-not-complete

  // regions, or we successfully claimed the region.

  HeapRegionRemSetIterator iter(hrrs);

  size_t card_index;

  // We claim cards in block so as to reduce the contention. The block size is determined by

  // the G1RSetScanBlockSize parameter.

  size_t jump_to_card = hrrs->iter_claimed_next(_block_size);

  for (size_t current_card = 0; iter.has_next(card_index); current_card++) {

    if (current_card >= jump_to_card + _block_size) {

      jump_to_card = hrrs->iter_claimed_next(_block_size);

    }

    if (current_card < jump_to_card) continue;

    HeapWord* card_start = _g1h->bot_shared()->address_for_index(card_index);

    HeapRegion* card_region = _g1h->heap_region_containing(card_start);

    _cards++;

    if (!card_region->is_on_dirty_cards_region_list()) {

      _g1h->push_dirty_cards_region(card_region);

    }

    // If the card is dirty, then we will scan it during updateRS.

    if (!card_region->in_collection_set() &&

        !_ct_bs->is_card_dirty(card_index)) {

      scanCard(card_index, card_region);

    }

  }

  if (!_try_claimed) {

    // Scan the strong code root list attached to the current region

    scan_strong_code_roots(r);

    hrrs->set_iter_complete();

  }

  return false;

}

size_t G1RemSet::scanRS(G1ParPushHeapRSClosure* oc,

                        CodeBlobClosure* heap_region_codeblobs,

                        uint worker_i) {

  double rs_time_start = os::elapsedTime();

  HeapRegion *startRegion = _g1->start_cset_region_for_worker(worker_i);

  ScanRSClosure scanRScl(oc, heap_region_codeblobs, worker_i);

  _g1->collection_set_iterate_from(startRegion, &scanRScl);

  scanRScl.set_try_claimed();

  _g1->collection_set_iterate_from(startRegion, &scanRScl);

  double scan_rs_time_sec = (os::elapsedTime() - rs_time_start)

                            - scanRScl.strong_code_root_scan_time_sec();

  _g1p->phase_times()->record_time_secs(G1GCPhaseTimes::ScanRS, worker_i, scan_rs_time_sec);

  _g1p->phase_times()->record_time_secs(G1GCPhaseTimes::CodeRoots, worker_i, scanRScl.strong_code_root_scan_time_sec());

  return scanRScl.cards_done();

}

// Closure used for updating RSets and recording references that

// point into the collection set. Only called during an

// evacuation pause.

class RefineRecordRefsIntoCSCardTableEntryClosure: public CardTableEntryClosure {

  G1RemSet* _g1rs;

  DirtyCardQueue* _into_cset_dcq;

public:

  RefineRecordRefsIntoCSCardTableEntryClosure(G1CollectedHeap* g1h,

                                              DirtyCardQueue* into_cset_dcq) :

    _g1rs(g1h->g1_rem_set()), _into_cset_dcq(into_cset_dcq)

  {}

  bool do_card_ptr(jbyte* card_ptr, uint worker_i) {

    // The only time we care about recording cards that

    // contain references that point into the collection set

    // is during RSet updating within an evacuation pause.

    // In this case worker_i should be the id of a GC worker thread.

    assert(SafepointSynchronize::is_at_safepoint(), "not during an evacuation pause");

    assert(worker_i < ParallelGCThreads, "should be a GC worker");

    if (_g1rs->refine_card(card_ptr, worker_i, true)) {

      // 'card_ptr' contains references that point into the collection

      // set. We need to record the card in the DCQS

      // (_into_cset_dirty_card_queue_set)

      // that's used for that purpose.

      //

      // Enqueue the card

      _into_cset_dcq->enqueue(card_ptr);

    }

    return true;

  }

};

void G1RemSet::updateRS(DirtyCardQueue* into_cset_dcq, uint worker_i) {

  RefineRecordRefsIntoCSCardTableEntryClosure into_cset_update_rs_cl(_g1, into_cset_dcq);

  G1GCParPhaseTimesTracker x(_g1p->phase_times(), G1GCPhaseTimes::UpdateRS, worker_i);

  {

    // Apply the closure to the entries of the hot card cache.

    G1GCParPhaseTimesTracker y(_g1p->phase_times(), G1GCPhaseTimes::ScanHCC, worker_i);

    _g1->iterate_hcc_closure(&into_cset_update_rs_cl, worker_i);

  }

  // Apply the closure to all remaining log entries.

  _g1->iterate_dirty_card_closure(&into_cset_update_rs_cl, worker_i);

}

void G1RemSet::cleanupHRRS() {

  HeapRegionRemSet::cleanup();

}

size_t G1RemSet::oops_into_collection_set_do(G1ParPushHeapRSClosure* oc,

                                             CodeBlobClosure* heap_region_codeblobs,

                                             uint worker_i) {

  // We cache the value of 'oc' closure into the appropriate slot in the

  // _cset_rs_update_cl for this worker

  assert(worker_i < n_workers(), "sanity");

  _cset_rs_update_cl[worker_i] = oc;

  // A DirtyCardQueue that is used to hold cards containing references

  // that point into the collection set. This DCQ is associated with a

  // special DirtyCardQueueSet (see g1CollectedHeap.hpp).  Under normal

  // circumstances (i.e. the pause successfully completes), these cards

  // are just discarded (there's no need to update the RSets of regions

  // that were in the collection set - after the pause these regions

  // are wholly 'free' of live objects. In the event of an evacuation

  // failure the cards/buffers in this queue set are passed to the

  // DirtyCardQueueSet that is used to manage RSet updates

  DirtyCardQueue into_cset_dcq(&_into_cset_dirty_card_queue_set);

  updateRS(&into_cset_dcq, worker_i);

  size_t cards_scanned = scanRS(oc, heap_region_codeblobs, worker_i);

  // We now clear the cached values of _cset_rs_update_cl for this worker

  _cset_rs_update_cl[worker_i] = NULL;

  return cards_scanned;

}

void G1RemSet::prepare_for_oops_into_collection_set_do() {

  _g1->set_refine_cte_cl_concurrency(false);

  DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();

  dcqs.concatenate_logs();

}

void G1RemSet::cleanup_after_oops_into_collection_set_do() {

  // Cleanup after copy

  _g1->set_refine_cte_cl_concurrency(true);

  // Set all cards back to clean.

  _g1->cleanUpCardTable();

  DirtyCardQueueSet& into_cset_dcqs = _into_cset_dirty_card_queue_set;

  int into_cset_n_buffers = into_cset_dcqs.completed_buffers_num();

  if (_g1->evacuation_failed()) {

    double restore_remembered_set_start = os::elapsedTime();

    // Restore remembered sets for the regions pointing into the collection set.

    // We just need to transfer the completed buffers from the DirtyCardQueueSet

    // used to hold cards that contain references that point into the collection set

    // to the DCQS used to hold the deferred RS updates.

    _g1->dirty_card_queue_set().merge_bufferlists(&into_cset_dcqs);

    _g1->g1_policy()->phase_times()->record_evac_fail_restore_remsets((os::elapsedTime() - restore_remembered_set_start) * 1000.0);

  }

  // Free any completed buffers in the DirtyCardQueueSet used to hold cards

  // which contain references that point into the collection.

  _into_cset_dirty_card_queue_set.clear();

  assert(_into_cset_dirty_card_queue_set.completed_buffers_num() == 0,

         "all buffers should be freed");

  _into_cset_dirty_card_queue_set.clear_n_completed_buffers();

}

class ScrubRSClosure: public HeapRegionClosure {

  G1CollectedHeap* _g1h;

  BitMap* _region_bm;

  BitMap* _card_bm;

  CardTableModRefBS* _ctbs;

public:

  ScrubRSClosure(BitMap* region_bm, BitMap* card_bm) :

    _g1h(G1CollectedHeap::heap()),

    _region_bm(region_bm), _card_bm(card_bm),

    _ctbs(_g1h->g1_barrier_set()) {}

  bool doHeapRegion(HeapRegion* r) {

    if (!r->is_continues_humongous()) {

      r->rem_set()->scrub(_ctbs, _region_bm, _card_bm);

    }

    return false;

  }

};

void G1RemSet::scrub(BitMap* region_bm, BitMap* card_bm, uint worker_num, HeapRegionClaimer *hrclaimer) {

  ScrubRSClosure scrub_cl(region_bm, card_bm);

  _g1->heap_region_par_iterate(&scrub_cl, worker_num, hrclaimer);

}

G1TriggerClosure::G1TriggerClosure() :

  _triggered(false) { }

G1InvokeIfNotTriggeredClosure::G1InvokeIfNotTriggeredClosure(G1TriggerClosure* t_cl,

                                                             OopClosure* oop_cl)  :

  _trigger_cl(t_cl), _oop_cl(oop_cl) { }

G1Mux2Closure::G1Mux2Closure(OopClosure *c1, OopClosure *c2) :

  _c1(c1), _c2(c2) { }

G1UpdateRSOrPushRefOopClosure::

G1UpdateRSOrPushRefOopClosure(G1CollectedHeap* g1h,

                              G1RemSet* rs,

                              G1ParPushHeapRSClosure* push_ref_cl,

                              bool record_refs_into_cset,

                              uint worker_i) :

  _g1(g1h), _g1_rem_set(rs), _from(NULL),

  _record_refs_into_cset(record_refs_into_cset),

  _push_ref_cl(push_ref_cl), _worker_i(worker_i) { }

// Returns true if the given card contains references that point

// into the collection set, if we're checking for such references;

// false otherwise.

bool G1RemSet::refine_card(jbyte* card_ptr, uint worker_i,

                           bool check_for_refs_into_cset) {

  assert(_g1->is_in_exact(_ct_bs->addr_for(card_ptr)),

         "Card at " PTR_FORMAT " index " SIZE_FORMAT " representing heap at " PTR_FORMAT " (%u) must be in committed heap",

         p2i(card_ptr),

         _ct_bs->index_for(_ct_bs->addr_for(card_ptr)),

         p2i(_ct_bs->addr_for(card_ptr)),

         _g1->addr_to_region(_ct_bs->addr_for(card_ptr)));

  // If the card is no longer dirty, nothing to do.

  if (*card_ptr != CardTableModRefBS::dirty_card_val()) {

    // No need to return that this card contains refs that point

    // into the collection set.

    return false;

  }

  // Construct the region representing the card.

  HeapWord* start = _ct_bs->addr_for(card_ptr);

  // And find the region containing it.

  HeapRegion* r = _g1->heap_region_containing(start);

  // Why do we have to check here whether a card is on a young region,

  // given that we dirty young regions and, as a result, the

  // post-barrier is supposed to filter them out and never to enqueue

  // them? When we allocate a new region as the "allocation region" we

  // actually dirty its cards after we release the lock, since card

  // dirtying while holding the lock was a performance bottleneck. So,

  // as a result, it is possible for other threads to actually

  // allocate objects in the region (after the acquire the lock)

  // before all the cards on the region are dirtied. This is unlikely,

  // and it doesn't happen often, but it can happen. So, the extra

  // check below filters out those cards.

  if (r->is_young()) {

    return false;

  }

  // While we are processing RSet buffers during the collection, we

  // actually don't want to scan any cards on the collection set,

  // since we don'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 deals with a reliability issue which

  // involves scanning a card in the collection set and coming across

  // an array that was being chunked and looking malformed. Note,

  // however, that if evacuation fails, we have to scan any objects

  // that were not moved and create any missing entries.

  if (r->in_collection_set()) {

    return false;

  }

  // The result from the hot card cache insert call is either:

  //   * pointer to the current card

  //     (implying that the current card is not 'hot'),

  //   * null

  //     (meaning we had inserted the card ptr into the "hot" card cache,

  //     which had some headroom),

  //   * a pointer to a "hot" card that was evicted from the "hot" cache.

  //

  G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();

  if (hot_card_cache->use_cache()) {

    assert(!check_for_refs_into_cset, "sanity");

    assert(!SafepointSynchronize::is_at_safepoint(), "sanity");

    card_ptr = hot_card_cache->insert(card_ptr);

    if (card_ptr == NULL) {

      // There was no eviction. Nothing to do.

      return false;

    }

    start = _ct_bs->addr_for(card_ptr);

    r = _g1->heap_region_containing(start);

    // Checking whether the region we got back from the cache

    // is young here is inappropriate. The region could have been

    // freed, reallocated and tagged as young while in the cache.

    // Hence we could see its young type change at any time.

  }

  // Don't use addr_for(card_ptr + 1) which can ask for

  // a card beyond the heap.  This is not safe without a perm

  // gen at the upper end of the heap.

  HeapWord* end   = start + CardTableModRefBS::card_size_in_words;

  MemRegion dirtyRegion(start, end);

  G1ParPushHeapRSClosure* oops_in_heap_closure = NULL;

  if (check_for_refs_into_cset) {

    // ConcurrentG1RefineThreads have worker numbers larger than what

    // _cset_rs_update_cl[] is set up to handle. But those threads should

    // only be active outside of a collection which means that when they

    // reach here they should have check_for_refs_into_cset == false.

    assert((size_t)worker_i < n_workers(), "index of worker larger than _cset_rs_update_cl[].length");

    oops_in_heap_closure = _cset_rs_update_cl[worker_i];

  }

  G1UpdateRSOrPushRefOopClosure update_rs_oop_cl(_g1,

                                                 _g1->g1_rem_set(),

                                                 oops_in_heap_closure,

                                                 check_for_refs_into_cset,

                                                 worker_i);

  update_rs_oop_cl.set_from(r);

  G1TriggerClosure trigger_cl;

  FilterIntoCSClosure into_cs_cl(_g1, &trigger_cl);

  G1InvokeIfNotTriggeredClosure invoke_cl(&trigger_cl, &into_cs_cl);

  G1Mux2Closure mux(&invoke_cl, &update_rs_oop_cl);

  FilterOutOfRegionClosure filter_then_update_rs_oop_cl(r,

                        (check_for_refs_into_cset ?

                                (OopClosure*)&mux :

                                (OopClosure*)&update_rs_oop_cl));

  // The region for the current card may be a young region. The

  // current card may have been a card that was evicted from the

  // card cache. When the card was inserted into the cache, we had

  // determined that its region was non-young. While in the cache,

  // the region may have been freed during a cleanup pause, reallocated

  // and tagged as young.

  //

  // We wish to filter out cards for such a region but the current

  // thread, if we're running concurrently, may "see" the young type

  // change at any time (so an earlier "is_young" check may pass or

  // fail arbitrarily). We tell the iteration code to perform this

  // filtering when it has been determined that there has been an actual

  // allocation in this region and making it safe to check the young type.

  bool filter_young = true;

  HeapWord* stop_point =

    r->oops_on_card_seq_iterate_careful(dirtyRegion,

                                        &filter_then_update_rs_oop_cl,