Mercurial > hg > graal-jvmci-8
view jvmci/jdk.vm.ci.hotspot/src/jdk/vm/ci/hotspot/HotSpotJVMCIMetaAccessContext.java @ 22697:57646377e480
Rename Compiler to JVMCICompiler and expose it from JVMCIRuntime.
author | Roland Schatz <roland.schatz@oracle.com> |
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date | Wed, 21 Oct 2015 13:47:47 +0200 |
parents | 1bbd4a7c274b |
children | 1d4ce2d19e52 |
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/* * Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved. * 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. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package jdk.vm.ci.hotspot; import java.lang.ref.Reference; import java.lang.ref.ReferenceQueue; import java.lang.ref.WeakReference; import java.util.Arrays; import java.util.Iterator; import java.util.Map; import java.util.WeakHashMap; import jdk.vm.ci.meta.JVMCIMetaAccessContext; import jdk.vm.ci.meta.JavaKind; import jdk.vm.ci.meta.ResolvedJavaType; /** * This class manages the set of metadata roots that must be scanned during garbage collection. * Because of class redefinition Method* and ConstantPool* can be freed if they don't appear to be * in use so they must be tracked when there are live references to them from Java. * * The general theory of operation is that all {@link MetaspaceWrapperObject}s are created by * calling into the VM which calls back out to actually create the wrapper instance. During the call * the VM keeps the metadata reference alive through the use of metadata handles. Once the call * completes the wrapper object is registered here and will be scanned during metadata scanning. The * weakness of the reference to the wrapper object allows them to be reclaimed when they are no * longer used. * */ public class HotSpotJVMCIMetaAccessContext implements JVMCIMetaAccessContext { /** * The set of currently live contexts used for tracking of live metadata. Examined from the VM * during garbage collection. */ private static WeakReference<?>[] allContexts = new WeakReference<?>[0]; /** * This is a chunked list of metadata roots. It can be read from VM native code so it's been * marked volatile to ensure the order of updates are respected. */ private volatile Object[] metadataRoots; private ChunkedList<WeakReference<MetaspaceWrapperObject>> list = new ChunkedList<>(); /** * The number of weak references freed since the last time the list was shrunk. */ private int freed; /** * The {@link ReferenceQueue} tracking the weak references created by this context. */ private final ReferenceQueue<MetaspaceWrapperObject> queue = new ReferenceQueue<>(); static synchronized void add(HotSpotJVMCIMetaAccessContext context) { for (int i = 0; i < allContexts.length; i++) { if (allContexts[i] == null || allContexts[i].get() == null) { allContexts[i] = new WeakReference<>(context); return; } } int index = allContexts.length; allContexts = Arrays.copyOf(allContexts, index + 2); allContexts[index] = new WeakReference<>(context); } HotSpotJVMCIMetaAccessContext() { add(this); } /** * Periodically trim the list of tracked metadata. A new list is created to replace the old to * avoid concurrent scanning issues. */ private void clean() { Reference<?> ref = queue.poll(); if (ref == null) { return; } while (ref != null) { freed++; ref = queue.poll(); } if (freed > list.size() / 2) { ChunkedList<WeakReference<MetaspaceWrapperObject>> newList = new ChunkedList<>(); for (WeakReference<MetaspaceWrapperObject> element : list) { /* * The referent could become null anywhere in here but it doesn't matter. It will * get cleaned up next time. */ if (element != null && element.get() != null) { newList.add(element); } } list = newList; metadataRoots = list.getHead(); freed = 0; } } /** * Add a {@link MetaspaceWrapperObject} to tracked by the GC. It's assumed that the caller is * responsible for keeping the reference alive for the duration of the call. Once registration * is complete then the VM will ensure it's kept alive. * * @param metaspaceObject */ public synchronized void add(MetaspaceWrapperObject metaspaceObject) { clean(); list.add(new WeakReference<>(metaspaceObject, queue)); if (list.getHead() != metadataRoots) { /* * The list enlarged so update the head. */ metadataRoots = list.getHead(); } } protected ResolvedJavaType createClass(Class<?> javaClass) { if (javaClass.isPrimitive()) { JavaKind kind = JavaKind.fromJavaClass(javaClass); return new HotSpotResolvedPrimitiveType(kind); } else { return new HotSpotResolvedObjectTypeImpl(javaClass, this); } } private final Map<Class<?>, WeakReference<ResolvedJavaType>> typeMap = new WeakHashMap<>(); @Override public synchronized ResolvedJavaType fromClass(Class<?> javaClass) { WeakReference<ResolvedJavaType> typeRef = typeMap.get(javaClass); ResolvedJavaType type = typeRef != null ? typeRef.get() : null; if (type == null) { type = createClass(javaClass); typeMap.put(javaClass, new WeakReference<>(type)); } return type; } /** * A very simple append only chunked list implementation. */ static class ChunkedList<T> implements Iterable<T> { private static final int CHUNK_SIZE = 32; private static final int NEXT_CHUNK_INDEX = CHUNK_SIZE - 1; private Object[] head; private int index; private int size; ChunkedList() { head = new Object[CHUNK_SIZE]; index = 0; } void add(T element) { if (index == NEXT_CHUNK_INDEX) { Object[] newHead = new Object[CHUNK_SIZE]; newHead[index] = head; head = newHead; index = 0; } head[index++] = element; size++; } Object[] getHead() { return head; } public Iterator<T> iterator() { return new ChunkIterator<>(); } int size() { return size; } class ChunkIterator<V> implements Iterator<V> { ChunkIterator() { currentChunk = head; currentIndex = -1; findNext(); } Object[] currentChunk; int currentIndex; V next; @SuppressWarnings("unchecked") V findNext() { V result; do { currentIndex++; if (currentIndex == NEXT_CHUNK_INDEX) { currentChunk = (Object[]) currentChunk[currentIndex]; currentIndex = 0; if (currentChunk == null) { return null; } } result = (V) currentChunk[currentIndex]; } while (result == null); return result; } public boolean hasNext() { return next != null; } public V next() { V result = next; next = findNext(); return result; } } } }