/*

 * Copyright (c) 2014, 2018, 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

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 */

#include "precompiled.hpp"

#include "gc/shared/blockOffsetTable.inline.hpp"

#include "gc/shared/cardGeneration.inline.hpp"

#include "gc/shared/cardTableRS.hpp"

#include "gc/shared/gcLocker.hpp"

#include "gc/shared/genCollectedHeap.hpp"

#include "gc/shared/genOopClosures.inline.hpp"

#include "gc/shared/generationSpec.hpp"

#include "gc/shared/space.inline.hpp"

#include "memory/iterator.hpp"

#include "memory/memRegion.hpp"

#include "logging/log.hpp"

#include "runtime/java.hpp"

CardGeneration::CardGeneration(ReservedSpace rs,

                               size_t initial_byte_size,

                               CardTableRS* remset) :

  Generation(rs, initial_byte_size), _rs(remset),

  _shrink_factor(0), _min_heap_delta_bytes(), _capacity_at_prologue(),

  _used_at_prologue()

{

  HeapWord* start = (HeapWord*)rs.base();

  size_t reserved_byte_size = rs.size();

  assert((uintptr_t(start) & 3) == 0, "bad alignment");

  assert((reserved_byte_size & 3) == 0, "bad alignment");

  MemRegion reserved_mr(start, heap_word_size(reserved_byte_size));

  _bts = new BlockOffsetSharedArray(reserved_mr,

                                    heap_word_size(initial_byte_size));

  MemRegion committed_mr(start, heap_word_size(initial_byte_size));

  _rs->resize_covered_region(committed_mr);

  if (_bts == NULL) {

    vm_exit_during_initialization("Could not allocate a BlockOffsetArray");

  }

  // Verify that the start and end of this generation is the start of a card.

  // If this wasn't true, a single card could span more than on generation,

  // which would cause problems when we commit/uncommit memory, and when we

  // clear and dirty cards.

  guarantee(_rs->is_aligned(reserved_mr.start()), "generation must be card aligned");

  if (reserved_mr.end() != GenCollectedHeap::heap()->reserved_region().end()) {

    // Don't check at the very end of the heap as we'll assert that we're probing off

    // the end if we try.

    guarantee(_rs->is_aligned(reserved_mr.end()), "generation must be card aligned");

  }

  _min_heap_delta_bytes = MinHeapDeltaBytes;

  _capacity_at_prologue = initial_byte_size;

  _used_at_prologue = 0;

}

bool CardGeneration::grow_by(size_t bytes) {

  assert_correct_size_change_locking();

  bool result = _virtual_space.expand_by(bytes);

  if (result) {

    size_t new_word_size =

       heap_word_size(_virtual_space.committed_size());

    MemRegion mr(space()->bottom(), new_word_size);

    // Expand card table

    GenCollectedHeap::heap()->rem_set()->resize_covered_region(mr);

    // Expand shared block offset array

    _bts->resize(new_word_size);

    // Fix for bug #4668531

    if (ZapUnusedHeapArea) {

      MemRegion mangle_region(space()->end(),

      (HeapWord*)_virtual_space.high());

      SpaceMangler::mangle_region(mangle_region);

    }

    // Expand space -- also expands space's BOT

    // (which uses (part of) shared array above)

    space()->set_end((HeapWord*)_virtual_space.high());

    // update the space and generation capacity counters

    update_counters();

    size_t new_mem_size = _virtual_space.committed_size();

    size_t old_mem_size = new_mem_size - bytes;

    log_trace(gc, heap)("Expanding %s from " SIZE_FORMAT "K by " SIZE_FORMAT "K to " SIZE_FORMAT "K",

                    name(), old_mem_size/K, bytes/K, new_mem_size/K);

  }

  return result;

}

bool CardGeneration::expand(size_t bytes, size_t expand_bytes) {

  assert_locked_or_safepoint(Heap_lock);

  if (bytes == 0) {

    return true;  // That's what grow_by(0) would return

  }

  size_t aligned_bytes  = ReservedSpace::page_align_size_up(bytes);

  if (aligned_bytes == 0){

    // The alignment caused the number of bytes to wrap.  An expand_by(0) will

    // return true with the implication that an expansion was done when it

    // was not.  A call to expand implies a best effort to expand by "bytes"

    // but not a guarantee.  Align down to give a best effort.  This is likely

    // the most that the generation can expand since it has some capacity to

    // start with.

    aligned_bytes = ReservedSpace::page_align_size_down(bytes);

  }

  size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);

  bool success = false;

  if (aligned_expand_bytes > aligned_bytes) {

    success = grow_by(aligned_expand_bytes);

  }

  if (!success) {

    success = grow_by(aligned_bytes);

  }

  if (!success) {

    success = grow_to_reserved();

  }

  if (success && GCLocker::is_active_and_needs_gc()) {

    log_trace(gc, heap)("Garbage collection disabled, expanded heap instead");

  }

  return success;

}

bool CardGeneration::grow_to_reserved() {

  assert_correct_size_change_locking();

  bool success = true;

  const size_t remaining_bytes = _virtual_space.uncommitted_size();

  if (remaining_bytes > 0) {

    success = grow_by(remaining_bytes);

    DEBUG_ONLY(if (!success) log_warning(gc)("grow to reserved failed");)

  }

  return success;

}

void CardGeneration::shrink(size_t bytes) {

  assert_correct_size_change_locking();

  size_t size = ReservedSpace::page_align_size_down(bytes);

  if (size == 0) {

    return;

  }

  // Shrink committed space

  _virtual_space.shrink_by(size);

  // Shrink space; this also shrinks the space's BOT

  space()->set_end((HeapWord*) _virtual_space.high());

  size_t new_word_size = heap_word_size(space()->capacity());

  // Shrink the shared block offset array

  _bts->resize(new_word_size);

  MemRegion mr(space()->bottom(), new_word_size);

  // Shrink the card table

  GenCollectedHeap::heap()->rem_set()->resize_covered_region(mr);

  size_t new_mem_size = _virtual_space.committed_size();

  size_t old_mem_size = new_mem_size + size;

  log_trace(gc, heap)("Shrinking %s from " SIZE_FORMAT "K to " SIZE_FORMAT "K",

                      name(), old_mem_size/K, new_mem_size/K);

}

// No young generation references, clear this generation's cards.

void CardGeneration::clear_remembered_set() {

  _rs->clear(reserved());

}

// Objects in this generation may have moved, invalidate this

// generation's cards.

void CardGeneration::invalidate_remembered_set() {

  _rs->invalidate(used_region());

}

void CardGeneration::compute_new_size() {

  assert(_shrink_factor <= 100, "invalid shrink factor");

  size_t current_shrink_factor = _shrink_factor;

  _shrink_factor = 0;

  // We don't have floating point command-line arguments

  // Note:  argument processing ensures that MinHeapFreeRatio < 100.

  const double minimum_free_percentage = MinHeapFreeRatio / 100.0;

  const double maximum_used_percentage = 1.0 - minimum_free_percentage;

  // Compute some numbers about the state of the heap.

  const size_t used_after_gc = used();

  const size_t capacity_after_gc = capacity();

  const double min_tmp = used_after_gc / maximum_used_percentage;

  size_t minimum_desired_capacity = (size_t)MIN2(min_tmp, double(max_uintx));

  // Don't shrink less than the initial generation size

  minimum_desired_capacity = MAX2(minimum_desired_capacity, initial_size());

  assert(used_after_gc <= minimum_desired_capacity, "sanity check");

    const size_t free_after_gc = free();

    const double free_percentage = ((double)free_after_gc) / capacity_after_gc;

    log_trace(gc, heap)("CardGeneration::compute_new_size:");

    log_trace(gc, heap)("    minimum_free_percentage: %6.2f  maximum_used_percentage: %6.2f",

                  minimum_free_percentage,

                  maximum_used_percentage);

    log_trace(gc, heap)("     free_after_gc   : %6.1fK   used_after_gc   : %6.1fK   capacity_after_gc   : %6.1fK",

                  free_after_gc / (double) K,

                  used_after_gc / (double) K,

                  capacity_after_gc / (double) K);

    log_trace(gc, heap)("     free_percentage: %6.2f", free_percentage);

  if (capacity_after_gc < minimum_desired_capacity) {

    // If we have less free space than we want then expand

    size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;

    // Don't expand unless it's significant

    if (expand_bytes >= _min_heap_delta_bytes) {

      expand(expand_bytes, 0); // safe if expansion fails

    }

    log_trace(gc, heap)("    expanding:  minimum_desired_capacity: %6.1fK  expand_bytes: %6.1fK  _min_heap_delta_bytes: %6.1fK",

                  minimum_desired_capacity / (double) K,

                  expand_bytes / (double) K,

                  _min_heap_delta_bytes / (double) K);

    return;

  }

  // No expansion, now see if we want to shrink

  size_t shrink_bytes = 0;

  // We would never want to shrink more than this

  size_t max_shrink_bytes = capacity_after_gc - minimum_desired_capacity;

  if (MaxHeapFreeRatio < 100) {

    const double maximum_free_percentage = MaxHeapFreeRatio / 100.0;

    const double minimum_used_percentage = 1.0 - maximum_free_percentage;

    const double max_tmp = used_after_gc / minimum_used_percentage;

    size_t maximum_desired_capacity = (size_t)MIN2(max_tmp, double(max_uintx));

    maximum_desired_capacity = MAX2(maximum_desired_capacity, initial_size());

    log_trace(gc, heap)("    maximum_free_percentage: %6.2f  minimum_used_percentage: %6.2f",

                             maximum_free_percentage, minimum_used_percentage);

    log_trace(gc, heap)("    _capacity_at_prologue: %6.1fK  minimum_desired_capacity: %6.1fK  maximum_desired_capacity: %6.1fK",

                             _capacity_at_prologue / (double) K,

                             minimum_desired_capacity / (double) K,

                             maximum_desired_capacity / (double) K);

    assert(minimum_desired_capacity <= maximum_desired_capacity,

           "sanity check");

    if (capacity_after_gc > maximum_desired_capacity) {

      // Capacity too large, compute shrinking size

      shrink_bytes = capacity_after_gc - maximum_desired_capacity;

      if (ShrinkHeapInSteps) {

        // If ShrinkHeapInSteps is true (the default),

        // we don't want to shrink all the way back to initSize if people call

        // System.gc(), because some programs do that between "phases" and then

        // we'd just have to grow the heap up again for the next phase.  So we

        // damp the shrinking: 0% on the first call, 10% on the second call, 40%

        // on the third call, and 100% by the fourth call.  But if we recompute

        // size without shrinking, it goes back to 0%.

        shrink_bytes = shrink_bytes / 100 * current_shrink_factor;

        if (current_shrink_factor == 0) {

          _shrink_factor = 10;

        } else {

          _shrink_factor = MIN2(current_shrink_factor * 4, (size_t) 100);

        }

      }

      assert(shrink_bytes <= max_shrink_bytes, "invalid shrink size");

      log_trace(gc, heap)("    shrinking:  initSize: %.1fK  maximum_desired_capacity: %.1fK",

                               initial_size() / (double) K, maximum_desired_capacity / (double) K);

      log_trace(gc, heap)("    shrink_bytes: %.1fK  current_shrink_factor: " SIZE_FORMAT "  new shrink factor: " SIZE_FORMAT "  _min_heap_delta_bytes: %.1fK",

                               shrink_bytes / (double) K,

                               current_shrink_factor,

                               _shrink_factor,

                               _min_heap_delta_bytes / (double) K);

    }

  }

  if (capacity_after_gc > _capacity_at_prologue) {

    // We might have expanded for promotions, in which case we might want to

    // take back that expansion if there's room after GC.  That keeps us from

    // stretching the heap with promotions when there's plenty of room.

    size_t expansion_for_promotion = capacity_after_gc - _capacity_at_prologue;

    expansion_for_promotion = MIN2(expansion_for_promotion, max_shrink_bytes);

    // We have two shrinking computations, take the largest

    shrink_bytes = MAX2(shrink_bytes, expansion_for_promotion);

    assert(shrink_bytes <= max_shrink_bytes, "invalid shrink size");

    log_trace(gc, heap)("    aggressive shrinking:  _capacity_at_prologue: %.1fK  capacity_after_gc: %.1fK  expansion_for_promotion: %.1fK  shrink_bytes: %.1fK",

                        capacity_after_gc / (double) K,

                        _capacity_at_prologue / (double) K,

                        expansion_for_promotion / (double) K,

                        shrink_bytes / (double) K);

  }

  // Don't shrink unless it's significant

  if (shrink_bytes >= _min_heap_delta_bytes) {

    shrink(shrink_bytes);

  }

}

// Currently nothing to do.

void CardGeneration::prepare_for_verify() {}

void CardGeneration::space_iterate(SpaceClosure* blk,

                                                 bool usedOnly) {

  blk->do_space(space());

}

void CardGeneration::younger_refs_iterate(OopsInGenClosure* blk, uint n_threads) {

  blk->set_generation(this);

  younger_refs_in_space_iterate(space(), blk, n_threads);

  blk->reset_generation();

}