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 * 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.
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 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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//
// The ObjectHeap is an abstraction over all generations in the VM
// It gives access to all present objects and classes.
//

package sun.jvm.hotspot.oops;

import java.util.*;

import sun.jvm.hotspot.debugger.*;
import sun.jvm.hotspot.gc.shared.*;
import sun.jvm.hotspot.gc.epsilon.*;
import sun.jvm.hotspot.gc.g1.*;
import sun.jvm.hotspot.gc.shenandoah.*;
import sun.jvm.hotspot.gc.parallel.*;
import sun.jvm.hotspot.gc.z.*;
import sun.jvm.hotspot.memory.*;
import sun.jvm.hotspot.runtime.*;
import sun.jvm.hotspot.types.*;
import sun.jvm.hotspot.utilities.*;

public class ObjectHeap {

  private static final boolean DEBUG;

  static {
    DEBUG = System.getProperty("sun.jvm.hotspot.oops.ObjectHeap.DEBUG") != null;
  }

  public ObjectHeap(TypeDataBase db) throws WrongTypeException {
    // Get commonly used sizes of basic types
    oopSize     = VM.getVM().getOopSize();
    byteSize    = db.getJByteType().getSize();
    charSize    = db.getJCharType().getSize();
    booleanSize = db.getJBooleanType().getSize();
    intSize     = db.getJIntType().getSize();
    shortSize   = db.getJShortType().getSize();
    longSize    = db.getJLongType().getSize();
    floatSize   = db.getJFloatType().getSize();
    doubleSize  = db.getJDoubleType().getSize();
  }

  
Comparison operation for oops, either or both of which may be null
/** Comparison operation for oops, either or both of which may be null */
public boolean equal(Oop o1, Oop o2) { if (o1 != null) return o1.equals(o2); return (o2 == null); } // Cached sizes of basic types private long oopSize; private long byteSize; private long charSize; private long booleanSize; private long intSize; private long shortSize; private long longSize; private long floatSize; private long doubleSize; public long getOopSize() { return oopSize; } public long getByteSize() { return byteSize; } public long getCharSize() { return charSize; } public long getBooleanSize() { return booleanSize; } public long getIntSize() { return intSize; } public long getShortSize() { return shortSize; } public long getLongSize() { return longSize; } public long getFloatSize() { return floatSize; } public long getDoubleSize() { return doubleSize; }
an interface to filter objects while walking heap
/** an interface to filter objects while walking heap */
public static interface ObjectFilter { public boolean canInclude(Oop obj); }
The base heap iteration mechanism
/** The base heap iteration mechanism */
public void iterate(HeapVisitor visitor) { iterateLiveRegions(collectLiveRegions(), visitor, null); }
iterate objects satisfying a specified ObjectFilter
/** iterate objects satisfying a specified ObjectFilter */
public void iterate(HeapVisitor visitor, ObjectFilter of) { iterateLiveRegions(collectLiveRegions(), visitor, of); }
iterate objects of given Klass. param 'includeSubtypes' tells whether to include objects of subtypes or not
/** iterate objects of given Klass. param 'includeSubtypes' tells whether to * include objects of subtypes or not */
public void iterateObjectsOfKlass(HeapVisitor visitor, final Klass k, boolean includeSubtypes) { if (includeSubtypes) { if (k.isFinal()) { // do the simpler "exact" klass loop iterateExact(visitor, k); } else { iterateSubtypes(visitor, k); } } else { // there can no object of abstract classes and interfaces if (!k.isAbstract() && !k.isInterface()) { iterateExact(visitor, k); } } }
iterate objects of given Klass (objects of subtypes included)
/** iterate objects of given Klass (objects of subtypes included) */
public void iterateObjectsOfKlass(HeapVisitor visitor, final Klass k) { iterateObjectsOfKlass(visitor, k, true); }
This routine can be used to iterate through the heap at an extremely low level (stepping word-by-word) to provide the ability to do very low-level debugging
/** This routine can be used to iterate through the heap at an extremely low level (stepping word-by-word) to provide the ability to do very low-level debugging */
public void iterateRaw(RawHeapVisitor visitor) { List<Address> liveRegions = collectLiveRegions(); // Summarize size long totalSize = 0; for (int i = 0; i < liveRegions.size(); i += 2) { Address bottom = (Address) liveRegions.get(i); Address top = (Address) liveRegions.get(i+1); totalSize += top.minus(bottom); } visitor.prologue(totalSize); for (int i = 0; i < liveRegions.size(); i += 2) { Address bottom = (Address) liveRegions.get(i); Address top = (Address) liveRegions.get(i+1); // Traverses the space from bottom to top while (bottom.lessThan(top)) { visitor.visitAddress(bottom); bottom = bottom.addOffsetTo(VM.getVM().getAddressSize()); } } visitor.epilogue(); } public boolean isValidMethod(Address handle) { try { Method m = (Method)Metadata.instantiateWrapperFor(handle); return true; } catch (Exception e) { return false; } } // Creates an instance from the Oop hierarchy based based on the handle public Oop newOop(OopHandle handle) { // The only known way to detect the right type of an oop is // traversing the class chain until a well-known klass is recognized. // A more direct solution would require the klasses to expose // the C++ vtbl structure. // Handle the null reference if (handle == null) return null; // Then check if obj.klass() is one of the root objects Klass klass = Oop.getKlassForOopHandle(handle); if (klass != null) { if (klass instanceof TypeArrayKlass) return new TypeArray(handle, this); if (klass instanceof ObjArrayKlass) return new ObjArray(handle, this); if (klass instanceof InstanceKlass) return new Instance(handle, this); } if (DEBUG) { System.err.println("Unknown oop at " + handle); System.err.println("Oop's klass is " + klass); } throw new UnknownOopException(); } // Print all objects in the object heap public void print() { HeapPrinter printer = new HeapPrinter(System.out); iterate(printer); } //--------------------------------------------------------------------------- // Internals only below this point // private void iterateExact(HeapVisitor visitor, final Klass k) { iterateLiveRegions(collectLiveRegions(), visitor, new ObjectFilter() { public boolean canInclude(Oop obj) { Klass tk = obj.getKlass(); // null Klass is seen sometimes! return (tk != null && tk.equals(k)); } }); } private void iterateSubtypes(HeapVisitor visitor, final Klass k) { iterateLiveRegions(collectLiveRegions(), visitor, new ObjectFilter() { public boolean canInclude(Oop obj) { Klass tk = obj.getKlass(); // null Klass is seen sometimes! return (tk != null && tk.isSubtypeOf(k)); } }); } private void iterateLiveRegions(List<Address> liveRegions, HeapVisitor visitor, ObjectFilter of) { // Summarize size long totalSize = 0; for (int i = 0; i < liveRegions.size(); i += 2) { Address bottom = (Address) liveRegions.get(i); Address top = (Address) liveRegions.get(i+1); totalSize += top.minus(bottom); } visitor.prologue(totalSize); for (int i = 0; i < liveRegions.size(); i += 2) { Address bottom = (Address) liveRegions.get(i); Address top = (Address) liveRegions.get(i+1); try { // Traverses the space from bottom to top OopHandle handle = bottom.addOffsetToAsOopHandle(0); while (handle.lessThan(top)) { Oop obj = null; obj = newOop(handle); if (obj == null) { throw new UnknownOopException(); } if (of == null || of.canInclude(obj)) { if (visitor.doObj(obj)) { // doObj() returns true to abort this loop. break; } } handle = handle.addOffsetToAsOopHandle(obj.getObjectSize()); } } catch (AddressException | UnknownOopException | WrongTypeException e) { // This is okay at the top of these regions } } visitor.epilogue(); } private static class LiveRegionsCollector implements LiveRegionsClosure { LiveRegionsCollector(List<Address> l) { liveRegions = l; } @Override public void doLiveRegions(LiveRegionsProvider lrp) { for (MemRegion reg : lrp.getLiveRegions()) { Address top = reg.end(); Address bottom = reg.start(); if (Assert.ASSERTS_ENABLED) { Assert.that(top != null, "top address in a live region should not be null"); } if (Assert.ASSERTS_ENABLED) { Assert.that(bottom != null, "bottom address in a live region should not be null"); } liveRegions.add(top); liveRegions.add(bottom); if (DEBUG) { System.err.println("Live region: " + lrp + ": " + bottom + ", " + top); } } } private List<Address> liveRegions; } // Returns a List<Address> where the addresses come in pairs. These // designate the live regions of the heap. private List<Address> collectLiveRegions() { // We want to iterate through all live portions of the heap, but // do not want to abort the heap traversal prematurely if we find // a problem (like an allocated but uninitialized object at the // top of a generation). To do this we enumerate all generations' // bottom and top regions, and factor in TLABs if necessary. // Addresses come in pairs. List<Address> liveRegions = new ArrayList<>(); LiveRegionsCollector lrc = new LiveRegionsCollector(liveRegions); CollectedHeap heap = VM.getVM().getUniverse().heap(); heap.liveRegionsIterate(lrc); // If UseTLAB is enabled, snip out regions associated with TLABs' // dead regions. Note that TLABs can be present in any generation. // FIXME: consider adding fewer boundaries to live region list. // Theoretically only need to stop at TLAB's top and resume at its // end. if (VM.getVM().getUseTLAB()) { Threads threads = VM.getVM().getThreads(); for (int i = 0; i < threads.getNumberOfThreads(); i++) { JavaThread thread = threads.getJavaThreadAt(i); ThreadLocalAllocBuffer tlab = thread.tlab(); if (tlab.start() != null) { if ((tlab.top() == null) || (tlab.end() == null)) { System.err.print("Warning: skipping invalid TLAB for thread "); thread.printThreadIDOn(System.err); System.err.println(); } else { if (DEBUG) { System.err.print("TLAB for " + thread.getThreadName() + ", #"); thread.printThreadIDOn(System.err); System.err.print(": "); tlab.printOn(System.err); } // Go from: // - below start() to start() // - start() to top() // - end() and above liveRegions.add(tlab.start()); liveRegions.add(tlab.start()); liveRegions.add(tlab.top()); liveRegions.add(tlab.hardEnd()); } } } } // Now sort live regions sortLiveRegions(liveRegions); if (Assert.ASSERTS_ENABLED) { Assert.that(liveRegions.size() % 2 == 0, "Must have even number of region boundaries"); } if (DEBUG) { System.err.println("liveRegions:"); for (int i = 0; i < liveRegions.size(); i += 2) { Address bottom = (Address) liveRegions.get(i); Address top = (Address) liveRegions.get(i+1); System.err.println(" " + bottom + " - " + top); } } return liveRegions; } private void sortLiveRegions(List<Address> liveRegions) { Collections.sort(liveRegions, new Comparator<Address>() { public int compare(Address a1, Address a2) { if (AddressOps.lt(a1, a2)) { return -1; } else if (AddressOps.gt(a1, a2)) { return 1; } return 0; } }); } }