1 /*
   2  * Copyright (c) 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 
  25 package sun.jvm.hotspot.gc.z;
  26 
  27 import java.util.HashMap;
  28 
  29 import sun.jvm.hotspot.runtime.VM;
  30 import sun.jvm.hotspot.utilities.BitMap;
  31 import sun.jvm.hotspot.utilities.BitMapInterface;
  32 
  33 /** Discontiguous bitmap for ZGC. */
  34 public class ZExternalBitMap implements BitMapInterface {
  35     private ZPageTable pageTable;
  36     private final long oopSize;
  37 
  38     private HashMap<ZPage, BitMap> pageToBitMap = new HashMap<ZPage, BitMap>();
  39 
  40     public ZExternalBitMap(ZCollectedHeap collectedHeap) {
  41         pageTable = collectedHeap.heap().pageTable();
  42         oopSize = VM.getVM().getOopSize();
  43     }
  44 
  45     private ZPage getPage(long zOffset) {
  46         if (zOffset > ZGlobals.ZAddressOffsetMask) {
  47             throw new RuntimeException("Not a Z offset: " + zOffset);
  48         }
  49 
  50         ZPage page = pageTable.get(ZUtils.longToAddress(zOffset));
  51         if (page == null) {
  52             throw new RuntimeException("Address not in pageTable: " + zOffset);
  53         }
  54         return page;
  55     }
  56 
  57     private BitMap getOrAddBitMap(ZPage page) {
  58         BitMap bitMap = pageToBitMap.get(page);
  59         if (bitMap == null) {
  60             long size = page.size();
  61 
  62             long maxNumObjects = size >>> page.object_alignment_shift();
  63             if (maxNumObjects > Integer.MAX_VALUE) {
  64                 throw new RuntimeException("int overflow");
  65             }
  66             int intMaxNumObjects = (int)maxNumObjects;
  67 
  68             bitMap = new BitMap(intMaxNumObjects);
  69             pageToBitMap.put(page,  bitMap);
  70         }
  71 
  72         return bitMap;
  73     }
  74 
  75     private int pageLocalBitMapIndex(ZPage page, long zOffset) {
  76         long pageLocalZOffset = zOffset - page.start();
  77         return (int)(pageLocalZOffset >>> page.object_alignment_shift());
  78     }
  79 
  80     private long convertToZOffset(long offset) {
  81         long addr = ZGlobals.ZAddressSpaceStart + oopSize * offset;
  82         return addr & ZGlobals.ZAddressOffsetMask;
  83     }
  84 
  85     @Override
  86     public boolean at(long offset) {
  87         long zOffset = convertToZOffset(offset);
  88         ZPage page = getPage(zOffset);
  89         BitMap bitMap = getOrAddBitMap(page);
  90         int index = pageLocalBitMapIndex(page, zOffset);
  91 
  92         return bitMap.at(index);
  93     }
  94 
  95     @Override
  96     public void atPut(long offset, boolean value) {
  97         long zOffset = convertToZOffset(offset);
  98         ZPage page = getPage(zOffset);
  99         BitMap bitMap = getOrAddBitMap(page);
 100         int index = pageLocalBitMapIndex(page, zOffset);
 101 
 102         bitMap.atPut(index, value);
 103     }
 104 
 105     @Override
 106     public void clear() {
 107         for (BitMap bitMap : pageToBitMap.values()) {
 108             bitMap.clear();
 109         }
 110     }
 111 }