1 /*

     2  * Copyright (c) 2015, 2019, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.

     8  *

     9  * This code is distributed in the hope that it will be useful, but WITHOUT

    10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    12  * version 2 for more details (a copy is included in the LICENSE file that

    13  * accompanied this code).

    14  *

    15  * You should have received a copy of the GNU General Public License version

    16  * 2 along with this work; if not, write to the Free Software Foundation,

    17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    18  *

    19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    20  * or visit www.oracle.com if you need additional information or have any

    21  * questions.

    22  */

    23 

    24 #include "precompiled.hpp"

    25 #include "gc/z/zForwarding.inline.hpp"

    26 #include "gc/z/zUtils.inline.hpp"

    27 #include "memory/allocation.hpp"

    28 #include "utilities/debug.hpp"

    29 

    30 ZForwarding::ZForwarding(uintptr_t start, size_t object_alignment_shift, uint32_t nentries) :

    31     _start(start),

    32     _object_alignment_shift(object_alignment_shift),

    33     _nentries(nentries),

    34     _refcount(1),

    35     _pinned(false) {}

    36 

    37 ZForwarding* ZForwarding::create(uintptr_t start, size_t object_alignment_shift, uint32_t live_objects) {

    38   assert(live_objects > 0, "Invalid value");

    39 

    40   // Allocate table for linear probing. The size of the table must be

    41   // a power of two to allow for quick and inexpensive indexing/masking.

    42   // The table is sized to have a load factor of 50%, i.e. sized to have

    43   // double the number of entries actually inserted.

    44   const uint32_t nentries = ZUtils::round_up_power_of_2(live_objects * 2);

    45 

    46   const size_t size = sizeof(ZForwarding) + (sizeof(ZForwardingEntry) * nentries);

    47   uint8_t* const addr = NEW_C_HEAP_ARRAY(uint8_t, size, mtGC);

    48   ZForwardingEntry* const entries = ::new (addr + sizeof(ZForwarding)) ZForwardingEntry[nentries];

    49   ZForwarding* const forwarding = ::new (addr) ZForwarding(start, object_alignment_shift, nentries);

    50   return forwarding;

    51 }

    52 

    53 void ZForwarding::destroy(ZForwarding* forwarding) {

    54   FREE_C_HEAP_ARRAY(uint8_t, forwarding);

    55 }

    56 

    57 void ZForwarding::verify(uint32_t object_max_count, uint32_t live_objects) const {

    58   uint32_t count = 0;

    59 

    60   for (ZForwardingCursor i = 0; i < _nentries; i++) {

    61     const ZForwardingEntry entry = at(&i);

    62     if (entry.is_empty()) {

    63       // Skip empty entries

    64       continue;

    65     }

    66 

    67     // Check from index

    68     guarantee(entry.from_index() < object_max_count, "Invalid from index");

    69 

    70     // Check for duplicates

    71     for (ZForwardingCursor j = i + 1; j < _nentries; j++) {

    72       const ZForwardingEntry other = at(&j);

    73       guarantee(entry.from_index() != other.from_index(), "Duplicate from");

    74       guarantee(entry.to_offset() != other.to_offset(), "Duplicate to");

    75     }

    76 

    77     count++;

    78   }

    79 

    80   // Check number of non-null entries

    81   guarantee(live_objects == count, "Count mismatch");

    82 }