C++ ParallelScavengeHeap::intra_heap_alignment方法代码示例

void PSYoungGen::compute_initial_space_boundaries() {
  ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
  assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");

  // Compute sizes
  size_t alignment = heap->intra_heap_alignment();
  size_t size = virtual_space()->committed_size();

  size_t survivor_size = size / InitialSurvivorRatio;
  survivor_size = align_size_down(survivor_size, alignment);
  // ... but never less than an alignment
  survivor_size = MAX2(survivor_size, alignment);

  // Young generation is eden + 2 survivor spaces
  size_t eden_size = size - (2 * survivor_size);

  // Now go ahead and set 'em.
  set_space_boundaries(eden_size, survivor_size);
  space_invariants();

  if (UsePerfData) {
    _eden_counters->update_capacity();
    _from_counters->update_capacity();
    _to_counters->update_capacity();
  }
}

// This method assumes that from-space has live data and that
// any shrinkage of the young gen is limited by location of
// from-space.
size_t PSYoungGen::available_to_live() {
  size_t delta_in_survivor = 0;
  ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
  const size_t space_alignment = heap->intra_heap_alignment();
  const size_t gen_alignment = heap->young_gen_alignment();

  MutableSpace* space_shrinking = NULL;
  if (from_space()->end() > to_space()->end()) {
    space_shrinking = from_space();
  } else {
    space_shrinking = to_space();
  }

  // Include any space that is committed but not included in
  // the survivor spaces.
  assert(((HeapWord*)virtual_space()->high()) >= space_shrinking->end(),
    "Survivor space beyond high end");
  size_t unused_committed = pointer_delta(virtual_space()->high(),
    space_shrinking->end(), sizeof(char));

  if (space_shrinking->is_empty()) {
    // Don't let the space shrink to 0
    assert(space_shrinking->capacity_in_bytes() >= space_alignment,
      "Space is too small");
    delta_in_survivor = space_shrinking->capacity_in_bytes() - space_alignment;
  } else {
    delta_in_survivor = pointer_delta(space_shrinking->end(),
                                      space_shrinking->top(),
                                      sizeof(char));
  }

  size_t delta_in_bytes = unused_committed + delta_in_survivor;
  delta_in_bytes = align_size_down(delta_in_bytes, gen_alignment);
  return delta_in_bytes;
}

void PSYoungGen::space_invariants() {
  ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
  const size_t alignment = heap->intra_heap_alignment();

  // Currently, our eden size cannot shrink to zero
  guarantee(eden_space()->capacity_in_bytes() >= alignment, "eden too small");
  guarantee(from_space()->capacity_in_bytes() >= alignment, "from too small");
  guarantee(to_space()->capacity_in_bytes() >= alignment, "to too small");

  // Relationship of spaces to each other
  char* eden_start = (char*)eden_space()->bottom();
  char* eden_end   = (char*)eden_space()->end();
  char* from_start = (char*)from_space()->bottom();
  char* from_end   = (char*)from_space()->end();
  char* to_start   = (char*)to_space()->bottom();
  char* to_end     = (char*)to_space()->end();

  guarantee(eden_start >= virtual_space()->low(), "eden bottom");
  guarantee(eden_start < eden_end, "eden space consistency");
  guarantee(from_start < from_end, "from space consistency");
  guarantee(to_start < to_end, "to space consistency");

  // Check whether from space is below to space
  if (from_start < to_start) {
    // Eden, from, to
    guarantee(eden_end <= from_start, "eden/from boundary");
    guarantee(from_end <= to_start,   "from/to boundary");
    guarantee(to_end <= virtual_space()->high(), "to end");
  } else {
    // Eden, to, from
    guarantee(eden_end <= to_start, "eden/to boundary");
    guarantee(to_end <= from_start, "to/from boundary");
    guarantee(from_end <= virtual_space()->high(), "from end");
  }

  // More checks that the virtual space is consistent with the spaces
  assert(virtual_space()->committed_size() >=
    (eden_space()->capacity_in_bytes() +
     to_space()->capacity_in_bytes() +
     from_space()->capacity_in_bytes()), "Committed size is inconsistent");
  assert(virtual_space()->committed_size() <= virtual_space()->reserved_size(),
    "Space invariant");
  char* eden_top = (char*)eden_space()->top();
  char* from_top = (char*)from_space()->top();
  char* to_top = (char*)to_space()->top();
  assert(eden_top <= virtual_space()->high(), "eden top");
  assert(from_top <= virtual_space()->high(), "from top");
  assert(to_top <= virtual_space()->high(), "to top");

  virtual_space()->verify();
}

// This method assumes that from-space has live data and that
// any shrinkage of the young gen is limited by location of
// from-space.
size_t ASParNewGeneration::available_to_live() const {
#undef SHRINKS_AT_END_OF_EDEN
#ifdef SHRINKS_AT_END_OF_EDEN
  size_t delta_in_survivor = 0;
  ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
  const size_t space_alignment = heap->intra_heap_alignment();
  const size_t gen_alignment = heap->object_heap_alignment();

  MutableSpace* space_shrinking = NULL;
  if (from_space()->end() > to_space()->end()) {
    space_shrinking = from_space();
  } else {
    space_shrinking = to_space();
  }

  // Include any space that is committed but not included in
  // the survivor spaces.
  assert(((HeapWord*)virtual_space()->high()) >= space_shrinking->end(),
    "Survivor space beyond high end");
  size_t unused_committed = pointer_delta(virtual_space()->high(),
    space_shrinking->end(), sizeof(char));

  if (space_shrinking->is_empty()) {
    // Don't let the space shrink to 0
    assert(space_shrinking->capacity_in_bytes() >= space_alignment,
      "Space is too small");
    delta_in_survivor = space_shrinking->capacity_in_bytes() - space_alignment;
  } else {
    delta_in_survivor = pointer_delta(space_shrinking->end(),
                                      space_shrinking->top(),
                                      sizeof(char));
  }

  size_t delta_in_bytes = unused_committed + delta_in_survivor;
  delta_in_bytes = align_size_down(delta_in_bytes, gen_alignment);
  return delta_in_bytes;
#else
  // The only space available for shrinking is in to-space if it
  // is above from-space.
  if (to()->bottom() > from()->bottom()) {
    const size_t alignment = os::vm_page_size();
    if (to()->capacity() < alignment) {
      return 0;
    } else {
      return to()->capacity() - alignment;
    }
  } else {
    return 0;
  }
#endif
}

// The current implementation only considers to the end of eden.
// If to_space is below from_space, to_space is not considered.
// to_space can be.
size_t ASPSYoungGen::available_to_live() {
  ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
  const size_t alignment = heap->intra_heap_alignment();

  // Include any space that is committed but is not in eden.
  size_t available = pointer_delta(eden_space()->bottom(),
                                   virtual_space()->low(),
                                   sizeof(char));

  const size_t eden_capacity = eden_space()->capacity_in_bytes();
  if (eden_space()->is_empty() && eden_capacity > alignment) {
    available += eden_capacity - alignment;
  }
  return available;
}

// Return the number of bytes the young gen is willing give up.
//
// Future implementations could check the survivors and if to_space is in the
// right place (below from_space), take a chunk from to_space.
size_t ASPSYoungGen::available_for_contraction() {

  size_t uncommitted_bytes = virtual_space()->uncommitted_size();
  if (uncommitted_bytes != 0) {
    return uncommitted_bytes;
  }

  if (eden_space()->is_empty()) {
    // Respect the minimum size for eden and for the young gen as a whole.
    ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
    const size_t eden_alignment = heap->intra_heap_alignment();
    const size_t gen_alignment = heap->young_gen_alignment();

    assert(eden_space()->capacity_in_bytes() >= eden_alignment,
      "Alignment is wrong");
    size_t eden_avail = eden_space()->capacity_in_bytes() - eden_alignment;
    eden_avail = align_size_down(eden_avail, gen_alignment);

    assert(virtual_space()->committed_size() >= min_gen_size(),
      "minimum gen size is wrong");
    size_t gen_avail = virtual_space()->committed_size() - min_gen_size();
    assert(virtual_space()->is_aligned(gen_avail), "not aligned");

    const size_t max_contraction = MIN2(eden_avail, gen_avail);
    // See comment for ASPSOldGen::available_for_contraction()
    // for reasons the "increment" fraction is used.
    PSAdaptiveSizePolicy* policy = heap->size_policy();
    size_t result = policy->eden_increment_aligned_down(max_contraction);
    size_t result_aligned = align_size_down(result, gen_alignment);
    if (PrintAdaptiveSizePolicy && Verbose) {
      gclog_or_tty->print_cr("ASPSYoungGen::available_for_contraction: %d K",
        result_aligned/K);
      gclog_or_tty->print_cr("  max_contraction %d K", max_contraction/K);
      gclog_or_tty->print_cr("  eden_avail %d K", eden_avail/K);
      gclog_or_tty->print_cr("  gen_avail %d K", gen_avail/K);
    }
    return result_aligned;

  }

  return 0;
}

void PSYoungGen::initialize_work() {

  _reserved = MemRegion((HeapWord*)virtual_space()->low_boundary(),
                        (HeapWord*)virtual_space()->high_boundary());

  MemRegion cmr((HeapWord*)virtual_space()->low(),
                (HeapWord*)virtual_space()->high());
  Universe::heap()->barrier_set()->resize_covered_region(cmr);

  if (ZapUnusedHeapArea) {
    // Mangle newly committed space immediately because it
    // can be done here more simply that after the new
    // spaces have been computed.
    SpaceMangler::mangle_region(cmr);
  }

  if (UseNUMA) {
    _eden_space = new MutableNUMASpace(virtual_space()->alignment());
  } else {
    _eden_space = new MutableSpace(virtual_space()->alignment());
  }
  _from_space = new MutableSpace(virtual_space()->alignment());
  _to_space   = new MutableSpace(virtual_space()->alignment());

  if (_eden_space == NULL || _from_space == NULL || _to_space == NULL) {
    vm_exit_during_initialization("Could not allocate a young gen space");
  }

  // Allocate the mark sweep views of spaces
  _eden_mark_sweep =
      new PSMarkSweepDecorator(_eden_space, NULL, MarkSweepDeadRatio);
  _from_mark_sweep =
      new PSMarkSweepDecorator(_from_space, NULL, MarkSweepDeadRatio);
  _to_mark_sweep =
      new PSMarkSweepDecorator(_to_space, NULL, MarkSweepDeadRatio);

  if (_eden_mark_sweep == NULL ||
      _from_mark_sweep == NULL ||
      _to_mark_sweep == NULL) {
    vm_exit_during_initialization("Could not complete allocation"
                                  " of the young generation");
  }

  // Generation Counters - generation 0, 3 subspaces
  _gen_counters = new PSGenerationCounters("new", 0, 3, _virtual_space);

  // Compute maximum space sizes for performance counters
  ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
  size_t alignment = heap->intra_heap_alignment();
  size_t size = virtual_space()->reserved_size();

  size_t max_survivor_size;
  size_t max_eden_size;

  if (UseAdaptiveSizePolicy) {
    max_survivor_size = size / MinSurvivorRatio;

    // round the survivor space size down to the nearest alignment
    // and make sure its size is greater than 0.
    max_survivor_size = align_size_down(max_survivor_size, alignment);
    max_survivor_size = MAX2(max_survivor_size, alignment);

    // set the maximum size of eden to be the size of the young gen
    // less two times the minimum survivor size. The minimum survivor
    // size for UseAdaptiveSizePolicy is one alignment.
    max_eden_size = size - 2 * alignment;
  } else {
    max_survivor_size = size / InitialSurvivorRatio;

    // round the survivor space size down to the nearest alignment
    // and make sure its size is greater than 0.
    max_survivor_size = align_size_down(max_survivor_size, alignment);
    max_survivor_size = MAX2(max_survivor_size, alignment);

    // set the maximum size of eden to be the size of the young gen
    // less two times the survivor size when the generation is 100%
    // committed. The minimum survivor size for -UseAdaptiveSizePolicy
    // is dependent on the committed portion (current capacity) of the
    // generation - the less space committed, the smaller the survivor
    // space, possibly as small as an alignment. However, we are interested
    // in the case where the young generation is 100% committed, as this
    // is the point where eden reachs its maximum size. At this point,
    // the size of a survivor space is max_survivor_size.
    max_eden_size = size - 2 * max_survivor_size;
  }

  _eden_counters = new SpaceCounters("eden", 0, max_eden_size, _eden_space,
                                     _gen_counters);
  _from_counters = new SpaceCounters("s0", 1, max_survivor_size, _from_space,
                                     _gen_counters);
  _to_counters = new SpaceCounters("s1", 2, max_survivor_size, _to_space,
                                   _gen_counters);

  compute_initial_space_boundaries();
}

void PSYoungGen::resize_spaces(size_t requested_eden_size,
                               size_t requested_survivor_size) {
  assert(UseAdaptiveSizePolicy, "sanity check");
  assert(requested_eden_size > 0  && requested_survivor_size > 0,
         "just checking");

  // We require eden and to space to be empty
  if ((!eden_space()->is_empty()) || (!to_space()->is_empty())) {
    return;
  }

  if (PrintAdaptiveSizePolicy && Verbose) {
    gclog_or_tty->print_cr("PSYoungGen::resize_spaces(requested_eden_size: "
                  SIZE_FORMAT
                  ", requested_survivor_size: " SIZE_FORMAT ")",
                  requested_eden_size, requested_survivor_size);
    gclog_or_tty->print_cr("    eden: [" PTR_FORMAT ".." PTR_FORMAT ") "
                  SIZE_FORMAT,
                  eden_space()->bottom(),
                  eden_space()->end(),
                  pointer_delta(eden_space()->end(),
                                eden_space()->bottom(),
                                sizeof(char)));
    gclog_or_tty->print_cr("    from: [" PTR_FORMAT ".." PTR_FORMAT ") "
                  SIZE_FORMAT,
                  from_space()->bottom(),
                  from_space()->end(),
                  pointer_delta(from_space()->end(),
                                from_space()->bottom(),
                                sizeof(char)));
    gclog_or_tty->print_cr("      to: [" PTR_FORMAT ".." PTR_FORMAT ") "
                  SIZE_FORMAT,
                  to_space()->bottom(),
                  to_space()->end(),
                  pointer_delta(  to_space()->end(),
                                  to_space()->bottom(),
                                  sizeof(char)));
  }

  // There's nothing to do if the new sizes are the same as the current
  if (requested_survivor_size == to_space()->capacity_in_bytes() &&
      requested_survivor_size == from_space()->capacity_in_bytes() &&
      requested_eden_size == eden_space()->capacity_in_bytes()) {
    if (PrintAdaptiveSizePolicy && Verbose) {
      gclog_or_tty->print_cr("    capacities are the right sizes, returning");
    }
    return;
  }

  char* eden_start = (char*)eden_space()->bottom();
  char* eden_end   = (char*)eden_space()->end();
  char* from_start = (char*)from_space()->bottom();
  char* from_end   = (char*)from_space()->end();
  char* to_start   = (char*)to_space()->bottom();
  char* to_end     = (char*)to_space()->end();

  ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
  const size_t alignment = heap->intra_heap_alignment();
  const bool maintain_minimum =
    (requested_eden_size + 2 * requested_survivor_size) <= min_gen_size();

  bool eden_from_to_order = from_start < to_start;
  // Check whether from space is below to space
  if (eden_from_to_order) {
    // Eden, from, to
    eden_from_to_order = true;
    if (PrintAdaptiveSizePolicy && Verbose) {
      gclog_or_tty->print_cr("  Eden, from, to:");
    }

    // Set eden
    // "requested_eden_size" is a goal for the size of eden
    // and may not be attainable.  "eden_size" below is
    // calculated based on the location of from-space and
    // the goal for the size of eden.  from-space is
    // fixed in place because it contains live data.
    // The calculation is done this way to avoid 32bit
    // overflow (i.e., eden_start + requested_eden_size
    // may too large for representation in 32bits).
    size_t eden_size;
    if (maintain_minimum) {
      // Only make eden larger than the requested size if
      // the minimum size of the generation has to be maintained.
      // This could be done in general but policy at a higher
      // level is determining a requested size for eden and that
      // should be honored unless there is a fundamental reason.
      eden_size = pointer_delta(from_start,
                                eden_start,
                                sizeof(char));
    } else {
      eden_size = MIN2(requested_eden_size,
                       pointer_delta(from_start, eden_start, sizeof(char)));
    }

    eden_end = eden_start + eden_size;
    assert(eden_end >= eden_start, "addition overflowed");

    // To may resize into from space as long as it is clear of live data.
    // From space must remain page aligned, though, so we need to do some
    // extra calculations.
//.........这里部分代码省略.........

void ASPSYoungGen::resize_spaces(size_t requested_eden_size,
                                 size_t requested_survivor_size) {
  assert(UseAdaptiveSizePolicy, "sanity check");
  assert(requested_eden_size > 0 && requested_survivor_size > 0,
         "just checking");

  space_invariants();

  // We require eden and to space to be empty
  if ((!eden_space()->is_empty()) || (!to_space()->is_empty())) {
    return;
  }

  if (PrintAdaptiveSizePolicy && Verbose) {
    gclog_or_tty->print_cr("PSYoungGen::resize_spaces(requested_eden_size: "
                  SIZE_FORMAT
                  ", requested_survivor_size: " SIZE_FORMAT ")",
                  requested_eden_size, requested_survivor_size);
    gclog_or_tty->print_cr("    eden: [" PTR_FORMAT ".." PTR_FORMAT ") "
                  SIZE_FORMAT,
                  eden_space()->bottom(),
                  eden_space()->end(),
                  pointer_delta(eden_space()->end(),
                                eden_space()->bottom(),
                                sizeof(char)));
    gclog_or_tty->print_cr("    from: [" PTR_FORMAT ".." PTR_FORMAT ") "
                  SIZE_FORMAT,
                  from_space()->bottom(),
                  from_space()->end(),
                  pointer_delta(from_space()->end(),
                                from_space()->bottom(),
                                sizeof(char)));
    gclog_or_tty->print_cr("      to: [" PTR_FORMAT ".." PTR_FORMAT ") "
                  SIZE_FORMAT,
                  to_space()->bottom(),
                  to_space()->end(),
                  pointer_delta(  to_space()->end(),
                                  to_space()->bottom(),
                                  sizeof(char)));
  }

  // There's nothing to do if the new sizes are the same as the current
  if (requested_survivor_size == to_space()->capacity_in_bytes() &&
      requested_survivor_size == from_space()->capacity_in_bytes() &&
      requested_eden_size == eden_space()->capacity_in_bytes()) {
    if (PrintAdaptiveSizePolicy && Verbose) {
      gclog_or_tty->print_cr("    capacities are the right sizes, returning");
    }
    return;
  }

  char* eden_start = (char*)virtual_space()->low();
  char* eden_end   = (char*)eden_space()->end();
  char* from_start = (char*)from_space()->bottom();
  char* from_end   = (char*)from_space()->end();
  char* to_start   = (char*)to_space()->bottom();
  char* to_end     = (char*)to_space()->end();

  assert(eden_start < from_start, "Cannot push into from_space");

  ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
  const size_t alignment = heap->intra_heap_alignment();
  const bool maintain_minimum =
    (requested_eden_size + 2 * requested_survivor_size) <= min_gen_size();

  bool eden_from_to_order = from_start < to_start;
  // Check whether from space is below to space
  if (eden_from_to_order) {
    // Eden, from, to

    if (PrintAdaptiveSizePolicy && Verbose) {
      gclog_or_tty->print_cr("  Eden, from, to:");
    }

    // Set eden
    // "requested_eden_size" is a goal for the size of eden
    // and may not be attainable.  "eden_size" below is
    // calculated based on the location of from-space and
    // the goal for the size of eden.  from-space is
    // fixed in place because it contains live data.
    // The calculation is done this way to avoid 32bit
    // overflow (i.e., eden_start + requested_eden_size
    // may too large for representation in 32bits).
    size_t eden_size;
    if (maintain_minimum) {
      // Only make eden larger than the requested size if
      // the minimum size of the generation has to be maintained.
      // This could be done in general but policy at a higher
      // level is determining a requested size for eden and that
      // should be honored unless there is a fundamental reason.
      eden_size = pointer_delta(from_start,
                                eden_start,
                                sizeof(char));
    } else {
      eden_size = MIN2(requested_eden_size,
                       pointer_delta(from_start, eden_start, sizeof(char)));
    }

    eden_end = eden_start + eden_size;
    assert(eden_end >= eden_start, "addition overflowed")
//.........这里部分代码省略.........