/*

 * Copyright (c) 2007 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 *

 */

# include "incls/_precompiled.incl"

# include "incls/_parCardTableModRefBS.cpp.incl"

void CardTableModRefBS::par_non_clean_card_iterate_work(Space* sp, MemRegion mr,

                                                        DirtyCardToOopClosure* dcto_cl,

                                                        MemRegionClosure* cl,

                                                        bool clear,

                                                        int n_threads) {

  if (n_threads > 0) {

    assert(n_threads == (int)ParallelGCThreads, "# worker threads != # requested!");

      // Make sure the LNC array is valid for the space.

    jbyte**   lowest_non_clean;

    uintptr_t lowest_non_clean_base_chunk_index;

    size_t    lowest_non_clean_chunk_size;

    get_LNC_array_for_space(sp, lowest_non_clean,

                            lowest_non_clean_base_chunk_index,

                            lowest_non_clean_chunk_size);

    int n_strides = n_threads * StridesPerThread;

    SequentialSubTasksDone* pst = sp->par_seq_tasks();

    pst->set_par_threads(n_threads);

    pst->set_n_tasks(n_strides);

    int stride = 0;

    while (!pst->is_task_claimed(/* reference */ stride)) {

      process_stride(sp, mr, stride, n_strides, dcto_cl, cl, clear,

                     lowest_non_clean,

                     lowest_non_clean_base_chunk_index,

                     lowest_non_clean_chunk_size);

    }

    if (pst->all_tasks_completed()) {

      // Clear lowest_non_clean array for next time.

      intptr_t first_chunk_index = addr_to_chunk_index(mr.start());

      uintptr_t last_chunk_index  = addr_to_chunk_index(mr.last());

      for (uintptr_t ch = first_chunk_index; ch <= last_chunk_index; ch++) {

        intptr_t ind = ch - lowest_non_clean_base_chunk_index;

        assert(0 <= ind && ind < (intptr_t)lowest_non_clean_chunk_size,

               "Bounds error");

        lowest_non_clean[ind] = NULL;

      }

    }

  }

}

void

CardTableModRefBS::

process_stride(Space* sp,

               MemRegion used,

               jint stride, int n_strides,

               DirtyCardToOopClosure* dcto_cl,

               MemRegionClosure* cl,

               bool clear,

               jbyte** lowest_non_clean,

               uintptr_t lowest_non_clean_base_chunk_index,

               size_t    lowest_non_clean_chunk_size) {

  // We don't have to go downwards here; it wouldn't help anyway,

  // because of parallelism.

  // Find the first card address of the first chunk in the stride that is

  // at least "bottom" of the used region.

  jbyte*    start_card  = byte_for(used.start());

  jbyte*    end_card    = byte_after(used.last());

  uintptr_t start_chunk = addr_to_chunk_index(used.start());

  uintptr_t start_chunk_stride_num = start_chunk % n_strides;

  jbyte* chunk_card_start;

  if ((uintptr_t)stride >= start_chunk_stride_num) {

    chunk_card_start = (jbyte*)(start_card +

                                (stride - start_chunk_stride_num) *

                                CardsPerStrideChunk);

  } else {

    // Go ahead to the next chunk group boundary, then to the requested stride.

    chunk_card_start = (jbyte*)(start_card +

                                (n_strides - start_chunk_stride_num + stride) *

                                CardsPerStrideChunk);

  }

  while (chunk_card_start < end_card) {

    // We don't have to go downwards here; it wouldn't help anyway,

    // because of parallelism.  (We take care with "min_done"; see below.)

    // Invariant: chunk_mr should be fully contained within the "used" region.

    jbyte*    chunk_card_end = chunk_card_start + CardsPerStrideChunk;

    MemRegion chunk_mr       = MemRegion(addr_for(chunk_card_start),

                                         chunk_card_end >= end_card ?

                                           used.end() : addr_for(chunk_card_end));

    assert(chunk_mr.word_size() > 0, "[chunk_card_start > used_end)");

    assert(used.contains(chunk_mr), "chunk_mr should be subset of used");

    // Process the chunk.

    process_chunk_boundaries(sp,

                             dcto_cl,

                             chunk_mr,

                             used,

                             lowest_non_clean,

                             lowest_non_clean_base_chunk_index,

                             lowest_non_clean_chunk_size);

    non_clean_card_iterate_work(chunk_mr, cl, clear);

    // Find the next chunk of the stride.

    chunk_card_start += CardsPerStrideChunk * n_strides;

  }

}

void

CardTableModRefBS::

process_chunk_boundaries(Space* sp,

                         DirtyCardToOopClosure* dcto_cl,

                         MemRegion chunk_mr,

                         MemRegion used,

                         jbyte** lowest_non_clean,

                         uintptr_t lowest_non_clean_base_chunk_index,

                         size_t    lowest_non_clean_chunk_size)

{

  // We must worry about the chunk boundaries.

  // First, set our max_to_do:

  HeapWord* max_to_do = NULL;

  uintptr_t cur_chunk_index = addr_to_chunk_index(chunk_mr.start());

  cur_chunk_index           = cur_chunk_index - lowest_non_clean_base_chunk_index;

  if (chunk_mr.end() < used.end()) {

    // This is not the last chunk in the used region.  What is the last

    // object?

    HeapWord* last_block = sp->block_start(chunk_mr.end());

    assert(last_block <= chunk_mr.end(), "In case this property changes.");

    if (last_block == chunk_mr.end()

        || !sp->block_is_obj(last_block)) {

      max_to_do = chunk_mr.end();

    } else {

      // It is an object and starts before the end of the current chunk.

      // last_obj_card is the card corresponding to the start of the last object

      // in the chunk.  Note that the last object may not start in

      // the chunk.

      jbyte* last_obj_card = byte_for(last_block);

      if (!card_may_have_been_dirty(*last_obj_card)) {

        // The card containing the head is not dirty.  Any marks in

        // subsequent cards still in this chunk must have been made

        // precisely; we can cap processing at the end.

        max_to_do = chunk_mr.end();

      } else {

        // The last object must be considered dirty, and extends onto the

        // following chunk.  Look for a dirty card in that chunk that will

        // bound our processing.

        jbyte* limit_card = NULL;

        size_t last_block_size = sp->block_size(last_block);

        jbyte* last_card_of_last_obj =

          byte_for(last_block + last_block_size - 1);

        jbyte* first_card_of_next_chunk = byte_for(chunk_mr.end());

        // This search potentially goes a long distance looking

        // for the next card that will be scanned.  For example,

        // an object that is an array of primitives will not

        // have any cards covering regions interior to the array

        // that will need to be scanned. The scan can be terminated

        // at the last card of the next chunk.  That would leave

        // limit_card as NULL and would result in "max_to_do"

        // being set with the LNC value or with the end

        // of the last block.

        jbyte* last_card_of_next_chunk = first_card_of_next_chunk +

          CardsPerStrideChunk;

        assert(byte_for(chunk_mr.end()) - byte_for(chunk_mr.start())

          == CardsPerStrideChunk, "last card of next chunk may be wrong");

        jbyte* last_card_to_check = (jbyte*) MIN2(last_card_of_last_obj,

                                                  last_card_of_next_chunk);

        for (jbyte* cur = first_card_of_next_chunk;

             cur <= last_card_to_check; cur++) {

          if (card_will_be_scanned(*cur)) {

            limit_card = cur; break;

          }

        }

        assert(0 <= cur_chunk_index+1 &&

               cur_chunk_index+1 < lowest_non_clean_chunk_size,

               "Bounds error.");

        // LNC for the next chunk

        jbyte* lnc_card = lowest_non_clean[cur_chunk_index+1];

        if (limit_card == NULL) {

          limit_card = lnc_card;

        }

        if (limit_card != NULL) {

          if (lnc_card != NULL) {

            limit_card = (jbyte*)MIN2((intptr_t)limit_card,

                                      (intptr_t)lnc_card);

          }

          max_to_do = addr_for(limit_card);

        } else {

          max_to_do = last_block + last_block_size;

        }

      }

    }

    assert(max_to_do != NULL, "OOPS!");

  } else {

    max_to_do = used.end();

  }

  // Now we can set the closure we're using so it doesn't to beyond

  // max_to_do.

  dcto_cl->set_min_done(max_to_do);

#ifndef PRODUCT

  dcto_cl->set_last_bottom(max_to_do);

#endif

  // Now we set *our" lowest_non_clean entry.

  // Find the object that spans our boundary, if one exists.

  // Nothing to do on the first chunk.

  if (chunk_mr.start() > used.start()) {

    // first_block is the block possibly spanning the chunk start

    HeapWord* first_block = sp->block_start(chunk_mr.start());

    // Does the block span the start of the chunk and is it

    // an object?

    if (first_block < chunk_mr.start() &&

        sp->block_is_obj(first_block)) {

      jbyte* first_dirty_card = NULL;

      jbyte* last_card_of_first_obj =

          byte_for(first_block + sp->block_size(first_block) - 1);

      jbyte* first_card_of_cur_chunk = byte_for(chunk_mr.start());

      jbyte* last_card_of_cur_chunk = byte_for(chunk_mr.last());

      jbyte* last_card_to_check =

        (jbyte*) MIN2((intptr_t) last_card_of_cur_chunk,

                      (intptr_t) last_card_of_first_obj);

      for (jbyte* cur = first_card_of_cur_chunk;

           cur <= last_card_to_check; cur++) {

        if (card_will_be_scanned(*cur)) {

          first_dirty_card = cur; break;

        }

      }

      if (first_dirty_card != NULL) {

        assert(0 <= cur_chunk_index &&

                 cur_chunk_index < lowest_non_clean_chunk_size,

               "Bounds error.");

        lowest_non_clean[cur_chunk_index] = first_dirty_card;

      }

    }

  }

}

void

CardTableModRefBS::

get_LNC_array_for_space(Space* sp,

                        jbyte**& lowest_non_clean,

                        uintptr_t& lowest_non_clean_base_chunk_index,

                        size_t& lowest_non_clean_chunk_size) {

  int       i        = find_covering_region_containing(sp->bottom());

  MemRegion covered  = _covered[i];

  size_t    n_chunks = chunks_to_cover(covered);

  // Only the first thread to obtain the lock will resize the

  // LNC array for the covered region.  Any later expansion can't affect

  // the used_at_save_marks region.

  // (I observed a bug in which the first thread to execute this would

  // resize, and then it would cause "expand_and_allocates" that would

  // Increase the number of chunks in the covered region.  Then a second

  // thread would come and execute this, see that the size didn't match,

  // and free and allocate again.  So the first thread would be using a

  // freed "_lowest_non_clean" array.)

  // Do a dirty read here. If we pass the conditional then take the rare

  // event lock and do the read again in case some other thread had already

  // succeeded and done the resize.

  int cur_collection = Universe::heap()->total_collections();

  if (_last_LNC_resizing_collection[i] != cur_collection) {

    MutexLocker x(ParGCRareEvent_lock);

    if (_last_LNC_resizing_collection[i] != cur_collection) {

      if (_lowest_non_clean[i] == NULL ||

          n_chunks != _lowest_non_clean_chunk_size[i]) {

        // Should we delete the old?

        if (_lowest_non_clean[i] != NULL) {

          assert(n_chunks != _lowest_non_clean_chunk_size[i],

                 "logical consequence");

          FREE_C_HEAP_ARRAY(CardPtr, _lowest_non_clean[i]);

          _lowest_non_clean[i] = NULL;

        }

        // Now allocate a new one if necessary.

        if (_lowest_non_clean[i] == NULL) {

          _lowest_non_clean[i]                  = NEW_C_HEAP_ARRAY(CardPtr, n_chunks);

          _lowest_non_clean_chunk_size[i]       = n_chunks;

          _lowest_non_clean_base_chunk_index[i] = addr_to_chunk_index(covered.start());

          for (int j = 0; j < (int)n_chunks; j++)

            _lowest_non_clean[i][j] = NULL;

        }

      }

      _last_LNC_resizing_collection[i] = cur_collection;

    }

  }

  // In any case, now do the initialization.

  lowest_non_clean                  = _lowest_non_clean[i];

  lowest_non_clean_base_chunk_index = _lowest_non_clean_base_chunk_index[i];

  lowest_non_clean_chunk_size       = _lowest_non_clean_chunk_size[i];

}