Esempio n. 1
0
void HRInto_G1RemSet::concurrentRefineOneCard_impl(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");

  HeapWord* end   = _ct_bs->addr_for(card_ptr + 1);
  MemRegion dirtyRegion(start, end);

#if CARD_REPEAT_HISTO
  init_ct_freq_table(_g1->g1_reserved_obj_bytes());
  ct_freq_note_card(_ct_bs->index_for(start));
#endif

  UpdateRSOopClosure update_rs_oop_cl(this, worker_i);
  update_rs_oop_cl.set_from(r);
  FilterOutOfRegionClosure filter_then_update_rs_oop_cl(r, &update_rs_oop_cl);

  // Undirty the card.
  *card_ptr = CardTableModRefBS::clean_card_val();
  // We must complete this write before we do any of the reads below.
  OrderAccess::storeload();
  // And process it, being careful of unallocated portions of TLAB's.
  HeapWord* stop_point =
    r->oops_on_card_seq_iterate_careful(dirtyRegion,
                                        &filter_then_update_rs_oop_cl);
  // If stop_point is non-null, then we encountered an unallocated region
  // (perhaps the unfilled portion of a TLAB.)  For now, we'll dirty the
  // card and re-enqueue: if we put off the card until a GC pause, then the
  // unallocated portion will be filled in.  Alternatively, we might try
  // the full complexity of the technique used in "regular" precleaning.
  if (stop_point != NULL) {
    // The card might have gotten re-dirtied and re-enqueued while we
    // worked.  (In fact, it's pretty likely.)
    if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
      *card_ptr = CardTableModRefBS::dirty_card_val();
      MutexLockerEx x(Shared_DirtyCardQ_lock,
                      Mutex::_no_safepoint_check_flag);
      DirtyCardQueue* sdcq =
        JavaThread::dirty_card_queue_set().shared_dirty_card_queue();
      sdcq->enqueue(card_ptr);
    }
  } else {
    out_of_histo.add_entry(filter_then_update_rs_oop_cl.out_of_region());
    _conc_refine_cards++;
  }
}
Esempio n. 2
0
bool G1RemSet::concurrentRefineOneCard_impl(jbyte* card_ptr, int worker_i,
                                                   bool check_for_refs_into_cset) {
  // 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");

  HeapWord* end   = _ct_bs->addr_for(card_ptr + 1);
  MemRegion dirtyRegion(start, end);

#if CARD_REPEAT_HISTO
  init_ct_freq_table(_g1->max_capacity());
  ct_freq_note_card(_ct_bs->index_for(start));
#endif

  assert(!check_for_refs_into_cset || _cset_rs_update_cl[worker_i] != NULL, "sanity");
  UpdateRSOrPushRefOopClosure update_rs_oop_cl(_g1,
                                               _g1->g1_rem_set(),
                                               _cset_rs_update_cl[worker_i],
                                               check_for_refs_into_cset,
                                               worker_i);
  update_rs_oop_cl.set_from(r);

  TriggerClosure trigger_cl;
  FilterIntoCSClosure into_cs_cl(NULL, _g1, &trigger_cl);
  InvokeIfNotTriggeredClosure invoke_cl(&trigger_cl, &into_cs_cl);
  Mux2Closure 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));

  // Undirty the card.
  *card_ptr = CardTableModRefBS::clean_card_val();
  // We must complete this write before we do any of the reads below.
  OrderAccess::storeload();
  // And process it, being careful of unallocated portions of TLAB's.

  // 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 conucrrently, 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,
                                        filter_young);

  // If stop_point is non-null, then we encountered an unallocated region
  // (perhaps the unfilled portion of a TLAB.)  For now, we'll dirty the
  // card and re-enqueue: if we put off the card until a GC pause, then the
  // unallocated portion will be filled in.  Alternatively, we might try
  // the full complexity of the technique used in "regular" precleaning.
  if (stop_point != NULL) {
    // The card might have gotten re-dirtied and re-enqueued while we
    // worked.  (In fact, it's pretty likely.)
    if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
      *card_ptr = CardTableModRefBS::dirty_card_val();
      MutexLockerEx x(Shared_DirtyCardQ_lock,
                      Mutex::_no_safepoint_check_flag);
      DirtyCardQueue* sdcq =
        JavaThread::dirty_card_queue_set().shared_dirty_card_queue();
      sdcq->enqueue(card_ptr);
    }
  } else {
    out_of_histo.add_entry(filter_then_update_rs_oop_cl.out_of_region());
    _conc_refine_cards++;
  }

  return trigger_cl.value();
}
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)),
         err_msg("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)),
                 _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);

#if CARD_REPEAT_HISTO
  init_ct_freq_table(_g1->max_capacity());
  ct_freq_note_card(_ct_bs->index_for(start));
#endif

  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(NULL, _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,
                                        filter_young,
                                        card_ptr);

  // If stop_point is non-null, then we encountered an unallocated region
  // (perhaps the unfilled portion of a TLAB.)  For now, we'll dirty the
  // card and re-enqueue: if we put off the card until a GC pause, then the
  // unallocated portion will be filled in.  Alternatively, we might try
  // the full complexity of the technique used in "regular" precleaning.
  if (stop_point != NULL) {
    // The card might have gotten re-dirtied and re-enqueued while we
    // worked.  (In fact, it's pretty likely.)
    if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
      *card_ptr = CardTableModRefBS::dirty_card_val();
      MutexLockerEx x(Shared_DirtyCardQ_lock,
                      Mutex::_no_safepoint_check_flag);
      DirtyCardQueue* sdcq =
        JavaThread::dirty_card_queue_set().shared_dirty_card_queue();
      sdcq->enqueue(card_ptr);
    }
  } else {
    _conc_refine_cards++;
  }

  // This gets set to true if the card being refined has
  // references that point into the collection set.
  bool has_refs_into_cset = trigger_cl.triggered();

  // We should only be detecting that the card contains references
  // that point into the collection set if the current thread is
  // a GC worker thread.
  assert(!has_refs_into_cset || SafepointSynchronize::is_at_safepoint(),
           "invalid result at non safepoint");

  return has_refs_into_cset;
}