jdk-24/hotspot/src/share/vm/gc/parallel/adjoiningVirtualSpaces.cpp

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * 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).
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 * 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.
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#include "precompiled.hpp"
#include "gc/parallel/adjoiningVirtualSpaces.hpp"
#include "memory/allocation.inline.hpp"
#include "runtime/java.hpp"

AdjoiningVirtualSpaces::AdjoiningVirtualSpaces(ReservedSpace rs,
                                               size_t min_low_byte_size,
                                               size_t min_high_byte_size,
                                               size_t alignment) :
  _reserved_space(rs), _min_low_byte_size(min_low_byte_size),
  _min_high_byte_size(min_high_byte_size), _low(0), _high(0),
  _alignment(alignment) {}

// The maximum byte sizes are for the initial layout of the
// virtual spaces and are not the limit on the maximum bytes sizes.
void AdjoiningVirtualSpaces::initialize(size_t max_low_byte_size,
                                        size_t init_low_byte_size,
                                        size_t init_high_byte_size) {

  // The reserved spaces for the two parts of the virtual space.
  ReservedSpace old_rs   = _reserved_space.first_part(max_low_byte_size);
  ReservedSpace young_rs = _reserved_space.last_part(max_low_byte_size);

  _low = new PSVirtualSpace(old_rs, alignment());
  if (!_low->expand_by(init_low_byte_size)) {
    vm_exit_during_initialization("Could not reserve enough space for "
                                  "object heap");
  }

  _high = new PSVirtualSpaceHighToLow(young_rs, alignment());
  if (!_high->expand_by(init_high_byte_size)) {
    vm_exit_during_initialization("Could not reserve enough space for "
                                  "object heap");
  }
}

bool AdjoiningVirtualSpaces::adjust_boundary_up(size_t change_in_bytes) {
  assert(UseAdaptiveSizePolicy && UseAdaptiveGCBoundary, "runtime check");
  size_t actual_change = low()->expand_into(high(), change_in_bytes);
  return actual_change != 0;
}

bool AdjoiningVirtualSpaces::adjust_boundary_down(size_t change_in_bytes) {
  assert(UseAdaptiveSizePolicy && UseAdaptiveGCBoundary, "runtime check");
  size_t actual_change = high()->expand_into(low(), change_in_bytes);
  return actual_change != 0;
}