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* 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).
*
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package com.oracle.svm.core.genscavenge;
import org.graalvm.compiler.nodes.java.ArrayLengthNode;
import org.graalvm.compiler.options.Option;
import org.graalvm.compiler.word.Word;
import org.graalvm.nativeimage.Platform;
import org.graalvm.nativeimage.Platforms;
import org.graalvm.word.Pointer;
import org.graalvm.word.UnsignedWord;
import org.graalvm.word.WordFactory;
import com.oracle.svm.core.SubstrateUtil;
import com.oracle.svm.core.annotate.AlwaysInline;
import com.oracle.svm.core.annotate.NeverInline;
import com.oracle.svm.core.annotate.RestrictHeapAccess;
import com.oracle.svm.core.heap.ObjectVisitor;
import com.oracle.svm.core.hub.DynamicHub;
import com.oracle.svm.core.hub.InteriorObjRefWalker;
import com.oracle.svm.core.hub.LayoutEncoding;
import com.oracle.svm.core.log.Log;
import com.oracle.svm.core.option.HostedOptionKey;
import com.oracle.svm.core.snippets.KnownIntrinsics;
import com.oracle.svm.core.util.VMError;
Run an ObjectReferenceVisitor (GreyToBlackObjRefVisitor) over any interior object references in the Object, turning this Object from grey to black. This visitor is used during GC and so it must be constructed during native image generation. /**
* Run an ObjectReferenceVisitor ({@link GreyToBlackObjRefVisitor}) over any interior object
* references in the Object, turning this Object from grey to black.
*
* This visitor is used during GC and so it must be constructed during native image generation.
*/
final class GreyToBlackObjectVisitor implements ObjectVisitor {
private final DiagnosticReporter diagnosticReporter;
private final GreyToBlackObjRefVisitor objRefVisitor;
@Platforms(Platform.HOSTED_ONLY.class)
GreyToBlackObjectVisitor(GreyToBlackObjRefVisitor greyToBlackObjRefVisitor) {
this.objRefVisitor = greyToBlackObjRefVisitor;
if (DiagnosticReporter.getHistoryLength() > 0) {
this.diagnosticReporter = new DiagnosticReporter();
SubstrateUtil.DiagnosticThunkRegister.getSingleton().register(diagnosticReporter);
} else {
this.diagnosticReporter = null;
}
}
public void reset() {
if (diagnosticReporter != null) {
diagnosticReporter.reset();
}
}
@Override
@NeverInline("Non-performance critical version")
public boolean visitObject(Object o) {
throw VMError.shouldNotReachHere("For performance reasons, this should not be called.");
}
@Override
@AlwaysInline("GC performance")
public boolean visitObjectInline(Object o) {
if (diagnosticReporter != null) {
diagnosticReporter.noteObject(o);
}
ReferenceObjectProcessing.discoverIfReference(o, objRefVisitor);
InteriorObjRefWalker.walkObjectInline(o, objRefVisitor);
return true;
}
A ring buffer of visited objects for diagnostics. /** A ring buffer of visited objects for diagnostics. */
static final class DiagnosticReporter implements SubstrateUtil.DiagnosticThunk {
static class Options {
@Option(help = "Length of GreyToBlackObjectVisitor history for diagnostics. 0 implies no history is kept.") //
static final HostedOptionKey<Integer> GreyToBlackObjectVisitorDiagnosticHistory = new HostedOptionKey<>(0);
}
The total count of all noted objects, used to compute the current array index. /** The total count of all noted objects, used to compute the current array index. */
private long historyCount;
The history of objects. Kept as pointers to avoid holding references. /** The history of objects. Kept as pointers to avoid holding references. */
private final Word[] objectHistory;
The history of the headers of the objects in objectHistory. /** The history of the headers of the objects in {@link #objectHistory}. */
private final UnsignedWord[] headerHistory;
@Platforms(Platform.HOSTED_ONLY.class)
DiagnosticReporter() {
this.historyCount = 0;
this.objectHistory = new Word[getHistoryLength()];
this.headerHistory = new UnsignedWord[getHistoryLength()];
}
Forget all history. /** Forget all history. */
public void reset() {
historyCount = 0;
for (int i = 0; i < getHistoryLength(); i += 1) {
objectHistory[i] = WordFactory.zero();
headerHistory[i] = WordFactory.zero();
}
}
Note a historical object. /** Note a historical object. */
public void noteObject(Object o) {
int index = countToIndex(historyCount);
objectHistory[index] = Word.objectToUntrackedPointer(o);
headerHistory[index] = ObjectHeaderImpl.readHeaderFromObjectCarefully(o);
historyCount += 1;
}
@Override
@RestrictHeapAccess(access = RestrictHeapAccess.Access.NO_ALLOCATION, reason = "Must not allocate during printing diagnostics.")
public void invokeWithoutAllocation(Log log) {
if (historyCount > 0) {
log.string("[GreyToBlackObjectVisitor.RealDiagnosticReporter.invoke:")
.string(" history / count: ")
.signed(getHistoryLength()).string(" / ").signed(historyCount)
.indent(true);
ImageHeapInfo imageHeapInfo = HeapImpl.getImageHeapInfo();
/*
* Report the history from the next available slot in the ring buffer. The older
* history is more reliable, since I have already used that to visit objects. The
* most recent history is more suspect, because this is the first use of it.
*/
for (int count = 0; count < getHistoryLength(); count += 1) {
int index = countToIndex(historyCount + count);
log.string(" index: ").unsigned(index, 3, Log.RIGHT_ALIGN);
Word objectEntry = objectHistory[index];
log.string(" objectEntry: ").hex(objectEntry);
UnsignedWord headerEntry = headerHistory[index];
Pointer headerHub = (Pointer) ObjectHeaderImpl.clearBits(headerEntry);
UnsignedWord headerHeaderBits = ObjectHeaderImpl.getHeaderBitsFromHeaderCarefully(headerEntry);
log.string(" headerEntry: ").hex(headerEntry).string(" = ").hex(headerHub).string(" | ").hex(headerHeaderBits).string(" / ");
boolean headerInImageHeap = imageHeapInfo.isInReadOnlyReferencePartition(headerHub) ||
imageHeapInfo.isInReadOnlyRelocatablePartition(headerHub);
if (headerInImageHeap) {
DynamicHub hub = (DynamicHub) KnownIntrinsics.convertUnknownValue(headerHub.toObject(), Object.class);
log.string(" class: ").string(hub.getName());
Object entryAsObject = KnownIntrinsics.convertUnknownValue(objectEntry.toObject(), Object.class);
if (LayoutEncoding.isArray(entryAsObject)) {
int length = ArrayLengthNode.arrayLength(entryAsObject);
log.string(" length: ").signed(length);
}
} else {
log.string(" header not in image heap");
}
log.newline();
}
log.string("]").indent(false).flush();
}
}
private static int getHistoryLength() {
return Options.GreyToBlackObjectVisitorDiagnosticHistory.getValue();
}
private static int countToIndex(long value) {
return (int) (value % getHistoryLength());
}
}
}