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[GR-40145] Honor @Contended. #4929

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Merged
merged 1 commit into from
Sep 22, 2022
Merged

[GR-40145] Honor @Contended. #4929

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3 changes: 3 additions & 0 deletions substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/SubstrateOptions.java
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Original file line number Diff line number Diff line change
Expand Up @@ -448,6 +448,9 @@ public Boolean getValue(OptionValues values) {
@Option(help = "Sets the step size (in bytes) for sequential prefetch instructions.")//
public static final HostedOptionKey<Integer> AllocatePrefetchStepSize = new HostedOptionKey<>(64);

@Option(help = "How many bytes to pad fields and classes marked @Contended with.") //
public static final HostedOptionKey<Integer> ContendedPaddingWidth = new HostedOptionKey<>(128);

/*
* Isolate tear down options.
*/
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102 changes: 77 additions & 25 deletions substratevm/src/com.oracle.svm.hosted/src/com/oracle/svm/hosted/meta/UniverseBuilder.java
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Original file line number Diff line number Diff line change
Expand Up @@ -39,6 +39,8 @@
import java.util.Optional;
import java.util.Set;
import java.util.concurrent.ForkJoinTask;
import java.util.function.Function;
import java.util.stream.Collectors;

import org.graalvm.collections.Pair;
import org.graalvm.compiler.core.common.NumUtil;
Expand Down Expand Up @@ -96,6 +98,7 @@
import com.oracle.svm.hosted.substitute.DeletedMethod;
import com.oracle.svm.util.ReflectionUtil;

import jdk.internal.vm.annotation.Contended;
import jdk.vm.ci.meta.ConstantPool;
import jdk.vm.ci.meta.ExceptionHandler;
import jdk.vm.ci.meta.JavaKind;
Expand Down Expand Up @@ -390,7 +393,7 @@ public static boolean isKnownImmutableType(Class<?> clazz) {
}

private void layoutInstanceFields() {
layoutInstanceFields(hUniverse.getObjectClass(), ConfigurationValues.getObjectLayout().getFirstFieldOffset(), new HostedField[0]);
layoutInstanceFields(hUniverse.getObjectClass(), ConfigurationValues.getObjectLayout().getFirstFieldOffset(), new HostedField[0], false);
}

private static boolean mustReserveLengthField(HostedInstanceClass clazz) {
Expand All @@ -405,7 +408,7 @@ private static boolean mustReserveLengthField(HostedInstanceClass clazz) {
return false;
}

private void layoutInstanceFields(HostedInstanceClass clazz, int superSize, HostedField[] superFields) {
private void layoutInstanceFields(HostedInstanceClass clazz, int superSize, HostedField[] superFields, boolean superFieldsContendedPadding) {
ArrayList<HostedField> rawFields = new ArrayList<>();
ArrayList<HostedField> orderedFields = new ArrayList<>();
ObjectLayout layout = ConfigurationValues.getObjectLayout();
Expand Down Expand Up @@ -433,30 +436,45 @@ private void layoutInstanceFields(HostedInstanceClass clazz, int superSize, Host
}
}

// Sort so that a) all Object fields are consecutive, and b) bigger types come first.
Collections.sort(rawFields, HostedUniverse.FIELD_COMPARATOR_RELAXED);

int nextOffset = startSize;
while (rawFields.size() > 0) {
boolean progress = false;
for (int i = 0; i < rawFields.size(); i++) {
HostedField field = rawFields.get(i);
int fieldSize = layout.sizeInBytes(field.getStorageKind());

if (nextOffset % fieldSize == 0) {
field.setLocation(nextOffset);
nextOffset += fieldSize;
boolean hasLeadingPadding = superFieldsContendedPadding;
boolean isClassContended = clazz.isAnnotationPresent(Contended.class);
if (!hasLeadingPadding && (isClassContended || (clazz.getSuperclass() != null && clazz.getSuperclass().isAnnotationPresent(Contended.class)))) {
nextOffset += getContendedPadding();
hasLeadingPadding = true;
}

rawFields.remove(i);
orderedFields.add(field);
progress = true;
break;
}
}
if (!progress) {
// Insert padding byte and try again.
nextOffset++;
int beginOfFieldsOffset = nextOffset;

/*
* Sort and group fields so that fields marked @Contended(tag) are grouped by their tag,
* placing unannotated fields first in the object, and so that within groups, a) all Object
* fields are consecutive, and b) bigger types come first.
*/
Object uncontendedSentinel = new Object();
Function<HostedField, Object> getAnnotationGroup = field -> Optional.ofNullable(field.getAnnotation(Contended.class)).<Object> map(Contended::value).orElse(uncontendedSentinel);
Map<Object, ArrayList<HostedField>> contentionGroups = rawFields.stream()
.sorted(HostedUniverse.FIELD_COMPARATOR_RELAXED)
.collect(Collectors.groupingBy(getAnnotationGroup, Collectors.toCollection(ArrayList::new)));

ArrayList<HostedField> uncontendedFields = contentionGroups.remove(uncontendedSentinel);
if (uncontendedFields != null) {
assert !uncontendedFields.isEmpty();
nextOffset = placeFields(uncontendedFields, nextOffset, orderedFields, layout);
}

for (ArrayList<HostedField> groupFields : contentionGroups.values()) {
boolean placedFieldsBefore = (nextOffset != beginOfFieldsOffset);
if (placedFieldsBefore || !hasLeadingPadding) {
nextOffset += getContendedPadding();
}
nextOffset = placeFields(groupFields, nextOffset, orderedFields, layout);
}

boolean fieldsTrailingPadding = !contentionGroups.isEmpty();
if (fieldsTrailingPadding) {
nextOffset += getContendedPadding();
}

int endOfFieldsOffset = nextOffset;
Expand All @@ -465,8 +483,6 @@ private void layoutInstanceFields(HostedInstanceClass clazz, int superSize, Host
* Compute the offsets of the "synthetic" fields for this class (but not subclasses).
* Synthetic fields are put after all the instance fields. They are included in the instance
* size, but not in the offset passed to subclasses.
*
* TODO: Should there be a list of synthetic fields for a class?
*/

// A reference to a {@link java.util.concurrent.locks.ReentrantLock for "synchronized" or
Expand All @@ -478,6 +494,11 @@ private void layoutInstanceFields(HostedInstanceClass clazz, int superSize, Host
nextOffset += referenceFieldAlignmentAndSize;
}

boolean placedSyntheticFields = (nextOffset != endOfFieldsOffset);
if (isClassContended && (contentionGroups.isEmpty() || placedSyntheticFields)) {
nextOffset += getContendedPadding();
}

clazz.instanceFieldsWithoutSuper = orderedFields.toArray(new HostedField[orderedFields.size()]);
clazz.instanceSize = layout.alignUp(nextOffset);
clazz.afterFieldsOffset = nextOffset;
Expand All @@ -499,9 +520,40 @@ private void layoutInstanceFields(HostedInstanceClass clazz, int superSize, Host
* possible because each class that needs a synthetic field gets its own synthetic
* field at the end of its instance fields.
*/
layoutInstanceFields((HostedInstanceClass) subClass, endOfFieldsOffset, clazz.instanceFieldsWithSuper);
layoutInstanceFields((HostedInstanceClass) subClass, endOfFieldsOffset, clazz.instanceFieldsWithSuper, fieldsTrailingPadding);
}
}
}

private static int getContendedPadding() {
Integer value = SubstrateOptions.ContendedPaddingWidth.getValue();
return (value > 0) ? value : 0; // no alignment required, placing fields takes care of it
}

private static int placeFields(ArrayList<HostedField> fields, int firstOffset, ArrayList<HostedField> orderedFields, ObjectLayout layout) {
int nextOffset = firstOffset;
while (!fields.isEmpty()) {
boolean progress = false;
for (int i = 0; i < fields.size(); i++) {
HostedField field = fields.get(i);
int fieldSize = layout.sizeInBytes(field.getStorageKind());

if (nextOffset % fieldSize == 0) {
field.setLocation(nextOffset);
nextOffset += fieldSize;

fields.remove(i);
orderedFields.add(field);
progress = true;
break;
}
}
if (!progress) {
// Insert padding byte and try again.
nextOffset++;
}
}
return nextOffset;
}

private void layoutStaticFields() {
Expand Down