/*

 * 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/bufferingOopClosure.hpp"

#include "gc_implementation/g1/concurrentG1Refine.hpp"

#include "gc_implementation/g1/concurrentG1RefineThread.hpp"

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

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

#include "gc_implementation/g1/g1CollectorPolicy.hpp"

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

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

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

#include "memory/iterator.hpp"

#include "oops/oop.inline.hpp"

#include "utilities/intHisto.hpp"

#define CARD_REPEAT_HISTO 0

#if CARD_REPEAT_HISTO

static size_t ct_freq_sz;

static jbyte* ct_freq = NULL;

void init_ct_freq_table(size_t heap_sz_bytes) {

  if (ct_freq == NULL) {

    ct_freq_sz = heap_sz_bytes/CardTableModRefBS::card_size;

    ct_freq = new jbyte[ct_freq_sz];

    for (size_t j = 0; j < ct_freq_sz; j++) ct_freq[j] = 0;

  }

}

void ct_freq_note_card(size_t index) {

  assert(0 <= index && index < ct_freq_sz, "Bounds error.");

  if (ct_freq[index] < 100) { ct_freq[index]++; }

}

static IntHistogram card_repeat_count(10, 10);

void ct_freq_update_histo_and_reset() {

  for (size_t j = 0; j < ct_freq_sz; j++) {

    card_repeat_count.add_entry(ct_freq[j]);

    ct_freq[j] = 0;

  }

}

#endif

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),

    _cards_scanned(NULL), _total_cards_scanned(0)

{

  _seq_task = new SubTasksDone(NumSeqTasks);

  guarantee(n_workers() > 0, "There should be some workers");

  _cset_rs_update_cl = NEW_C_HEAP_ARRAY(OopsInHeapRegionClosure*, n_workers());

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

    _cset_rs_update_cl[i] = NULL;

  }

}

G1RemSet::~G1RemSet() {

  delete _seq_task;

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

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

  }

  FREE_C_HEAP_ARRAY(OopsInHeapRegionClosure*, _cset_rs_update_cl);

}

void CountNonCleanMemRegionClosure::do_MemRegion(MemRegion mr) {

  if (_g1->is_in_g1_reserved(mr.start())) {

    _n += (int) ((mr.byte_size() / CardTableModRefBS::card_size));

    if (_start_first == NULL) _start_first = mr.start();

  }

}

class ScanRSClosure : public HeapRegionClosure {

  size_t _cards_done, _cards;

  G1CollectedHeap* _g1h;

  OopsInHeapRegionClosure* _oc;

  G1BlockOffsetSharedArray* _bot_shared;

  CardTableModRefBS *_ct_bs;

  int _worker_i;

  int _block_size;

  bool _try_claimed;

public:

  ScanRSClosure(OopsInHeapRegionClosure* oc, int worker_i) :

    _oc(oc),

    _cards(0),

    _cards_done(0),

    _worker_i(worker_i),

    _try_claimed(false)

  {

    _g1h = G1CollectedHeap::heap();

    _bot_shared = _g1h->bot_shared();

    _ct_bs = (CardTableModRefBS*) (_g1h->barrier_set());

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

  }

  void set_try_claimed() { _try_claimed = true; }

  void scanCard(size_t index, HeapRegion *r) {

    // Stack allocate the DirtyCardToOopClosure instance

    HeapRegionDCTOC cl(_g1h, r, _oc,

                       CardTableModRefBS::Precise,

                       HeapRegionDCTOC::IntoCSFilterKind);

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

    _oc->set_region(r);

    HeapWord* card_start = _bot_shared->address_for_index(index);

    HeapWord* card_end = card_start + G1BlockOffsetSharedArray::N_words;

    Space *sp = SharedHeap::heap()->space_containing(card_start);

    MemRegion sm_region = sp->used_region_at_save_marks();

    MemRegion mr = sm_region.intersection(MemRegion(card_start,card_end));

    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 printCard(HeapRegion* card_region, size_t card_index,

                 HeapWord* card_start) {

    gclog_or_tty->print_cr("T %d Region [" PTR_FORMAT ", " PTR_FORMAT ") "

                           "RS names card %p: "

                           "[" PTR_FORMAT ", " PTR_FORMAT ")",

                           _worker_i,

                           card_region->bottom(), card_region->end(),

                           card_index,

                           card_start, card_start + G1BlockOffsetSharedArray::N_words);

  }

  bool 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 = _g1h->rem_set_iterator(_worker_i);

    hrrs->init_iterator(iter);

    size_t card_index;

    // We claim cards in block so as to recude 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);

#if 0

      gclog_or_tty->print("Rem set iteration yielded card [" PTR_FORMAT ", " PTR_FORMAT ").\n",

                          card_start, card_start + CardTableModRefBS::card_size_in_words);

#endif

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

      assert(card_region != NULL, "Yielding cards not in the heap?");

      _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) {

      hrrs->set_iter_complete();

    }

    return false;

  }

  size_t cards_done() { return _cards_done;}

  size_t cards_looked_up() { return _cards;}

};

// We want the parallel threads to start their scanning at

// different collection set regions to avoid contention.

// If we have:

//          n collection set regions

//          p threads

// Then thread t will start at region t * floor (n/p)

HeapRegion* G1RemSet::calculateStartRegion(int worker_i) {

  HeapRegion* result = _g1p->collection_set();

  if (ParallelGCThreads > 0) {

    int n_workers = _g1->workers()->total_workers();

    size_t cs_spans = cs_size / n_workers;

    size_t ind      = cs_spans * worker_i;

    for (size_t i = 0; i < ind; i++)

      result = result->next_in_collection_set();

  }

  return result;

}

void G1RemSet::scanRS(OopsInHeapRegionClosure* oc, int worker_i) {

  double rs_time_start = os::elapsedTime();

  HeapRegion *startRegion = calculateStartRegion(worker_i);

  ScanRSClosure scanRScl(oc, 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;

  assert( _cards_scanned != NULL, "invariant" );

  _cards_scanned[worker_i] = scanRScl.cards_done();

  _g1p->record_scan_rs_time(worker_i, scan_rs_time_sec * 1000.0);

}

// 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, int 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 < (int) (ParallelGCThreads == 0 ? 1 : ParallelGCThreads), "should be a GC worker");

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

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

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

      // (G1CollectedHeap::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, int worker_i) {

  double start = os::elapsedTime();

  // Apply the given closure to all remaining log entries.

  RefineRecordRefsIntoCSCardTableEntryClosure into_cset_update_rs_cl(_g1, into_cset_dcq);

  _g1->iterate_dirty_card_closure(&into_cset_update_rs_cl, into_cset_dcq, false, worker_i);

  // Now there should be no dirty cards.

  if (G1RSLogCheckCardTable) {

    CountNonCleanMemRegionClosure cl(_g1);

    _ct_bs->mod_card_iterate(&cl);

    // XXX This isn't true any more: keeping cards of young regions

    // marked dirty broke it.  Need some reasonable fix.

    guarantee(cl.n() == 0, "Card table should be clean.");

  }

  _g1p->record_update_rs_time(worker_i, (os::elapsedTime() - start) * 1000.0);

}

class CountRSSizeClosure: public HeapRegionClosure {

  size_t _n;

  size_t _tot;

  size_t _max;

  HeapRegion* _max_r;

  enum {

    N = 20,

    MIN = 6

  };

  int _histo[N];

public:

  CountRSSizeClosure() : _n(0), _tot(0), _max(0), _max_r(NULL) {

    for (int i = 0; i < N; i++) _histo[i] = 0;

  }

  bool doHeapRegion(HeapRegion* r) {

    if (!r->continuesHumongous()) {

      size_t occ = r->rem_set()->occupied();

      _n++;

      _tot += occ;

      if (occ > _max) {

        _max = occ;

        _max_r = r;

      }

      // Fit it into a histo bin.

      int s = 1 << MIN;

      int i = 0;

      while (occ > (size_t) s && i < (N-1)) {

        s = s << 1;

        i++;

      }

      _histo[i]++;

    }

    return false;

  }

  size_t n() { return _n; }

  size_t tot() { return _tot; }

  size_t mx() { return _max; }

  HeapRegion* mxr() { return _max_r; }

  void print_histo() {

    int mx = N;

    while (mx >= 0) {

      if (_histo[mx-1] > 0) break;

      mx--;

    }

    gclog_or_tty->print_cr("Number of regions with given RS sizes:");

    gclog_or_tty->print_cr("           <= %8d   %8d", 1 << MIN, _histo[0]);

    for (int i = 1; i < mx-1; i++) {

      gclog_or_tty->print_cr("  %8d  - %8d   %8d",

                    (1 << (MIN + i - 1)) + 1,

                    1 << (MIN + i),

                    _histo[i]);

    }

    gclog_or_tty->print_cr("            > %8d   %8d", (1 << (MIN+mx-2))+1, _histo[mx-1]);

  }

};

void G1RemSet::cleanupHRRS() {

  HeapRegionRemSet::cleanup();

}

void G1RemSet::oops_into_collection_set_do(OopsInHeapRegionClosure* oc,

                                             int worker_i) {

#if CARD_REPEAT_HISTO

  ct_freq_update_histo_and_reset();

#endif

  if (worker_i == 0) {

    _cg1r->clear_and_record_card_counts();

  }

  // Make this into a command-line flag...

  if (G1RSCountHisto && (ParallelGCThreads == 0 || worker_i == 0)) {

    CountRSSizeClosure count_cl;

    _g1->heap_region_iterate(&count_cl);

    gclog_or_tty->print_cr("Avg of %d RS counts is %f, max is %d, "

                  "max region is " PTR_FORMAT,

                  count_cl.n(), (float)count_cl.tot()/(float)count_cl.n(),

                  count_cl.mx(), count_cl.mxr());

    count_cl.print_histo();

  }

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

  // _cset_rs_update_cl for this worker

  assert(worker_i < (int)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 deferred

  //   RSet updates, or

  // * scanned for references that point into the collection set

  //   and the RSet of the corresponding region in the collection set

  //   is updated immediately.

  DirtyCardQueue into_cset_dcq(&_g1->into_cset_dirty_card_queue_set());

  assert((ParallelGCThreads > 0) || worker_i == 0, "invariant");

  // The two flags below were introduced temporarily to serialize

  // the updating and scanning of remembered sets. There are some

  // race conditions when these two operations are done in parallel

  // and they are causing failures. When we resolve said race

  // conditions, we'll revert back to parallel remembered set

  // updating and scanning. See CRs 6677707 and 6677708.

  if (G1UseParallelRSetUpdating || (worker_i == 0)) {

    updateRS(&into_cset_dcq, worker_i);

  } else {

    _g1p->record_update_rs_processed_buffers(worker_i, 0.0);

    _g1p->record_update_rs_time(worker_i, 0.0);

  }

  if (G1UseParallelRSetScanning || (worker_i == 0)) {

    scanRS(oc, worker_i);

  } else {

    _g1p->record_scan_rs_time(worker_i, 0.0);

  }

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

  _cset_rs_update_cl[worker_i] = NULL;

}

void G1RemSet::prepare_for_oops_into_collection_set_do() {

  cleanupHRRS();

  ConcurrentG1Refine* cg1r = _g1->concurrent_g1_refine();

  _g1->set_refine_cte_cl_concurrency(false);

  DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();

  dcqs.concatenate_logs();

  if (ParallelGCThreads > 0) {

    _seq_task->set_n_threads((int)n_workers());

  }

  guarantee( _cards_scanned == NULL, "invariant" );

  _cards_scanned = NEW_C_HEAP_ARRAY(size_t, n_workers());

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

    _cards_scanned[i] = 0;

  }

  _total_cards_scanned = 0;

}

// This closure, applied to a DirtyCardQueueSet, is used to immediately

// update the RSets for the regions in the CSet. For each card it iterates

// through the oops which coincide with that card. It scans the reference

// fields in each oop; when it finds an oop that points into the collection

// set, the RSet for the region containing the referenced object is updated.

class UpdateRSetCardTableEntryIntoCSetClosure: public CardTableEntryClosure {

  G1CollectedHeap* _g1;

  CardTableModRefBS* _ct_bs;

public:

  UpdateRSetCardTableEntryIntoCSetClosure(G1CollectedHeap* g1,

                                          CardTableModRefBS* bs):

    _g1(g1), _ct_bs(bs)

  { }

  bool do_card_ptr(jbyte* card_ptr, int worker_i) {

    // 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);

    assert(r != NULL, "unexpected null");

    // Scan oops in the card looking for references into the collection set

    HeapWord* end   = _ct_bs->addr_for(card_ptr + 1);

    MemRegion scanRegion(start, end);

    UpdateRSetImmediate update_rs_cl(_g1->g1_rem_set());

    FilterIntoCSClosure update_rs_cset_oop_cl(NULL, _g1, &update_rs_cl);

    FilterOutOfRegionClosure filter_then_update_rs_cset_oop_cl(r, &update_rs_cset_oop_cl);

    // We can pass false as the "filter_young" parameter here as:

    // * we should be in a STW pause,

    // * the DCQS to which this closure is applied is used to hold

    //   references that point into the collection set from the prior

    //   RSet updating,

    // * the post-write barrier shouldn't be logging updates to young

    //   regions (but there is a situation where this can happen - see

    //   the comment in G1RemSet::concurrentRefineOneCard below -

    //   that should not be applicable here), and

    // * during actual RSet updating, the filtering of cards in young

    //   regions in HeapRegion::oops_on_card_seq_iterate_careful is

    //   employed.

    // As a result, when this closure is applied to "refs into cset"

    // DCQS, we shouldn't see any cards in young regions.

    update_rs_cl.set_region(r);

    HeapWord* stop_point =

      r->oops_on_card_seq_iterate_careful(scanRegion,

                                          &filter_then_update_rs_cset_oop_cl,

                                          false /* filter_young */,

                                          NULL  /* card_ptr */);

    // Since this is performed in the event of an evacuation failure, we

    // we shouldn't see a non-null stop point

    assert(stop_point == NULL, "saw an unallocated region");

    return true;

  }

};

void G1RemSet::cleanup_after_oops_into_collection_set_do() {

  guarantee( _cards_scanned != NULL, "invariant" );

  _total_cards_scanned = 0;

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

    _total_cards_scanned += _cards_scanned[i];