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 package jdk.vm.ci.hotspot;
24
25 import java.lang.ref.Reference;
26 import java.lang.ref.ReferenceQueue;
27 import java.lang.ref.WeakReference;
28 import java.util.Arrays;
29 import java.util.Iterator;
30 import java.util.Map;
31 import java.util.WeakHashMap;
32
33 import jdk.vm.ci.meta.JVMCIMetaAccessContext;
34 import jdk.vm.ci.meta.JavaKind;
35 import jdk.vm.ci.meta.ResolvedJavaType;
36
37 /**
38 * This class manages the set of metadata roots that must be scanned during garbage collection.
39 * Because of class redefinition Method* and ConstantPool* can be freed if they don't appear to be
40 * in use so they must be tracked when there are live references to them from Java.
41 *
42 * The general theory of operation is that all {@link MetaspaceWrapperObject}s are created by
43 * calling into the VM which calls back out to actually create the wrapper instance. During the call
44 * the VM keeps the metadata reference alive through the use of metadata handles. Once the call
45 * completes the wrapper object is registered here and will be scanned during metadata scanning. The
46 * weakness of the reference to the wrapper object allows them to be reclaimed when they are no
47 * longer used.
48 *
49 */
50 public class HotSpotJVMCIMetaAccessContext implements JVMCIMetaAccessContext {
51
52 /**
53 * The set of currently live contexts used for tracking of live metadata. Examined from the VM
54 * during garbage collection.
55 */
56 private static WeakReference<?>[] allContexts = new WeakReference<?>[0];
57
58 /**
59 * This is a chunked list of metadata roots. It can be read from VM native code so it's been
60 * marked volatile to ensure the order of updates are respected.
61 */
62 private volatile Object[] metadataRoots;
63
64 private ChunkedList<WeakReference<MetaspaceWrapperObject>> list = new ChunkedList<>();
65
66 /**
67 * The number of weak references freed since the last time the list was shrunk.
68 */
69 private int freed;
70
132 list.add(new WeakReference<>(metaspaceObject, queue));
133 if (list.getHead() != metadataRoots) {
134 /*
135 * The list enlarged so update the head.
136 */
137 metadataRoots = list.getHead();
138 }
139 }
140
141 protected ResolvedJavaType createClass(Class<?> javaClass) {
142 if (javaClass.isPrimitive()) {
143 JavaKind kind = JavaKind.fromJavaClass(javaClass);
144 return new HotSpotResolvedPrimitiveType(kind);
145 } else {
146 return new HotSpotResolvedObjectTypeImpl(javaClass, this);
147 }
148 }
149
150 private final Map<Class<?>, WeakReference<ResolvedJavaType>> typeMap = new WeakHashMap<>();
151
152 @Override
153 public synchronized ResolvedJavaType fromClass(Class<?> javaClass) {
154 WeakReference<ResolvedJavaType> typeRef = typeMap.get(javaClass);
155 ResolvedJavaType type = typeRef != null ? typeRef.get() : null;
156 if (type == null) {
157 type = createClass(javaClass);
158 typeMap.put(javaClass, new WeakReference<>(type));
159 }
160 return type;
161 }
162
163 /**
164 * A very simple append only chunked list implementation.
165 */
166 static class ChunkedList<T> implements Iterable<T> {
167 private static final int CHUNK_SIZE = 32;
168
169 private static final int NEXT_CHUNK_INDEX = CHUNK_SIZE - 1;
170
171 private Object[] head;
172 private int index;
|
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 package jdk.vm.ci.hotspot;
24
25 import java.lang.ref.Reference;
26 import java.lang.ref.ReferenceQueue;
27 import java.lang.ref.WeakReference;
28 import java.util.Arrays;
29 import java.util.Iterator;
30 import java.util.Map;
31 import java.util.WeakHashMap;
32
33 import jdk.vm.ci.meta.JavaKind;
34 import jdk.vm.ci.meta.ResolvedJavaType;
35
36 /**
37 * This class manages the set of metadata roots that must be scanned during garbage collection.
38 * Because of class redefinition Method* and ConstantPool* can be freed if they don't appear to be
39 * in use so they must be tracked when there are live references to them from Java.
40 *
41 * The general theory of operation is that all {@link MetaspaceWrapperObject}s are created by
42 * calling into the VM which calls back out to actually create the wrapper instance. During the call
43 * the VM keeps the metadata reference alive through the use of metadata handles. Once the call
44 * completes the wrapper object is registered here and will be scanned during metadata scanning. The
45 * weakness of the reference to the wrapper object allows them to be reclaimed when they are no
46 * longer used.
47 *
48 */
49 public class HotSpotJVMCIMetaAccessContext {
50
51 /**
52 * The set of currently live contexts used for tracking of live metadata. Examined from the VM
53 * during garbage collection.
54 */
55 private static WeakReference<?>[] allContexts = new WeakReference<?>[0];
56
57 /**
58 * This is a chunked list of metadata roots. It can be read from VM native code so it's been
59 * marked volatile to ensure the order of updates are respected.
60 */
61 private volatile Object[] metadataRoots;
62
63 private ChunkedList<WeakReference<MetaspaceWrapperObject>> list = new ChunkedList<>();
64
65 /**
66 * The number of weak references freed since the last time the list was shrunk.
67 */
68 private int freed;
69
131 list.add(new WeakReference<>(metaspaceObject, queue));
132 if (list.getHead() != metadataRoots) {
133 /*
134 * The list enlarged so update the head.
135 */
136 metadataRoots = list.getHead();
137 }
138 }
139
140 protected ResolvedJavaType createClass(Class<?> javaClass) {
141 if (javaClass.isPrimitive()) {
142 JavaKind kind = JavaKind.fromJavaClass(javaClass);
143 return new HotSpotResolvedPrimitiveType(kind);
144 } else {
145 return new HotSpotResolvedObjectTypeImpl(javaClass, this);
146 }
147 }
148
149 private final Map<Class<?>, WeakReference<ResolvedJavaType>> typeMap = new WeakHashMap<>();
150
151 /**
152 * Gets the JVMCI mirror for a {@link Class} object.
153 *
154 * @return the {@link ResolvedJavaType} corresponding to {@code javaClass}
155 */
156 public synchronized ResolvedJavaType fromClass(Class<?> javaClass) {
157 WeakReference<ResolvedJavaType> typeRef = typeMap.get(javaClass);
158 ResolvedJavaType type = typeRef != null ? typeRef.get() : null;
159 if (type == null) {
160 type = createClass(javaClass);
161 typeMap.put(javaClass, new WeakReference<>(type));
162 }
163 return type;
164 }
165
166 /**
167 * A very simple append only chunked list implementation.
168 */
169 static class ChunkedList<T> implements Iterable<T> {
170 private static final int CHUNK_SIZE = 32;
171
172 private static final int NEXT_CHUNK_INDEX = CHUNK_SIZE - 1;
173
174 private Object[] head;
175 private int index;
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