[GR-43225] [GR-43635] [GR-43632] Optional identity hash code field and GC policy improvements.

substratevm/mx.substratevm/testhello.py

@@ -57,7 +57,7 @@ def __init__(self, name, regexps):
         self.name = name
         if not isinstance(regexps, list):
             regexps = [regexps]
-        self.rexps = [re.compile(regexp) for regexp in regexps]
+        self.rexps = [re.compile(r) for r in regexps if r is not None]
 
     # Check that successive lines of a gdb command's output text
     # match the corresponding regexp patterns provided when this
@@ -180,6 +180,9 @@ def test():
     # disable printing of address symbols
     execute("set print symbol off")
 
+    hub_ref_size = int(execute("printf \"%d\", sizeof('java.lang.Object'::__hub__)"))
+    fixed_idhash_field = (hub_ref_size > 4)
+
     # Print DefaultGreeter and check the modifiers of its methods and fields
     exec_string = execute("ptype 'hello.Hello$DefaultGreeter'")
     rexp = [r"type = class hello\.Hello\$DefaultGreeter : public hello\.Hello\$Greeter {",
@@ -241,7 +244,7 @@ def test():
                 r"%s<java.lang.Object> = {"%(spaces_pattern),
                 r"%s<_objhdr> = {"%(spaces_pattern),
                 r"%shub = %s,"%(spaces_pattern, address_pattern),
-                r"%sidHash = %s"%(spaces_pattern, address_pattern),
+                r"%sidHash = %s"%(spaces_pattern, address_pattern) if fixed_idhash_field else None,
                 r"%s}, <No data fields>}, "%(spaces_pattern),
                 r"%smembers of java\.lang\.String\[\]:"%(spaces_pattern),
                 r"%slen = 0x0,"%(spaces_pattern),
@@ -260,7 +263,7 @@ def test():
                     r"%s<java.lang.Object> = {"%(spaces_pattern),
                     r"%s<_objhdr> = {"%(spaces_pattern),
                     r"%shub = %s,"%(spaces_pattern, address_pattern),
-                    r"%sidHash = %s"%(spaces_pattern, address_pattern),
+                    r"%sidHash = %s"%(spaces_pattern, address_pattern) if fixed_idhash_field else None,
                     r"%s}, <No data fields>},"%(spaces_pattern),
                     r"%smembers of java\.lang\.Class:"%(spaces_pattern),
                     r"%sname = %s,"%(spaces_pattern, address_pattern),
@@ -270,7 +273,7 @@ def test():
                     r"%s<java.lang.Object> = {"%(spaces_pattern),
                     r"%s<_objhdr> = {"%(spaces_pattern),
                     r"%shub = %s,"%(spaces_pattern, address_pattern),
-                    r"%sidHash = %s"%(spaces_pattern, address_pattern),
+                    r"%sidHash = %s"%(spaces_pattern, address_pattern) if fixed_idhash_field else None,
                     r"%s}, <No data fields>},"%(spaces_pattern),
                     r"%smembers of java\.lang\.Class:"%(spaces_pattern),
                     r"%sname = %s,"%(spaces_pattern, address_pattern),
@@ -310,7 +313,7 @@ def test():
                 r"%s<java.lang.Object> = {"%(spaces_pattern),
                 r"%s<_objhdr> = {"%(spaces_pattern),
                 r"%shub = %s,"%(spaces_pattern, address_pattern),
-                r"%sidHash = %s"%(spaces_pattern, address_pattern),
+                r"%sidHash = %s"%(spaces_pattern, address_pattern) if fixed_idhash_field else None,
                 r"%s}, <No data fields>},"%(spaces_pattern),
                 r"%smembers of java\.lang\.Class:"%(spaces_pattern),
                 r"%sname = %s,"%(spaces_pattern, address_pattern),
@@ -426,12 +429,12 @@ def test():
     if isolates:
         rexp = [r"type = struct _objhdr {",
                 r"%s_z_\.java\.lang\.Class \*hub;"%(spaces_pattern),
-                r"%sint idHash;"%(spaces_pattern),
+                r"%sint idHash;"%(spaces_pattern) if fixed_idhash_field else None,
                 r"}"]
     else:
         rexp = [r"type = struct _objhdr {",
                 r"%sjava\.lang\.Class \*hub;"%(spaces_pattern),
-                r"%sint idHash;"%(spaces_pattern),
+                r"%sint idHash;"%(spaces_pattern) if fixed_idhash_field else None,
                 r"}"]
 
     checker = Checker('ptype _objhdr', rexp)

substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/AbstractCollectionPolicy.java

@@ -263,6 +263,17 @@ public int getTenuringAge() {
         return tenuringThreshold;
     }
 
+    @Override
+    public void onCollectionBegin(boolean completeCollection, long requestingNanoTime) {
+        // Capture the fraction of bytes in aligned chunks at the start to include all allocated
+        // (also dead) objects, because we use it to reserve aligned chunks for future allocations
+        UnsignedWord youngChunkBytes = GCImpl.getGCImpl().getAccounting().getYoungChunkBytesBefore();
+        if (youngChunkBytes.notEqual(0)) {
+            UnsignedWord youngAlignedChunkBytes = HeapImpl.getHeapImpl().getYoungGeneration().getAlignedChunkBytes();
+            avgYoungGenAlignedChunkFraction.sample(UnsignedUtils.toDouble(youngAlignedChunkBytes) / UnsignedUtils.toDouble(youngChunkBytes));
+        }
+    }
+
     @Override
     public UnsignedWord getMinimumHeapSize() {
         return sizes.minHeapSize;

substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/AdaptiveCollectionPolicy.java

@@ -94,11 +94,15 @@ class AdaptiveCollectionPolicy extends AbstractCollectionPolicy {
      * (disabled by default) which uses linear least-square fitting without discounting.
      */
     private static final boolean ADAPTIVE_SIZE_USE_COST_ESTIMATORS = true;
+    /** Number of space size adjustments before cost estimators are used. HotSpot default: 20. */
     private static final int ADAPTIVE_SIZE_POLICY_INITIALIZING_STEPS = ADAPTIVE_SIZE_POLICY_READY_THRESHOLD;
-    /** The minimum increase in throughput in percent for expanding a space by 1% of its size. */
-    private static final double ADAPTIVE_SIZE_ESTIMATOR_MIN_SIZE_COST_TRADEOFF = 0.5;
+    /**
+     * The minimum estimated decrease in {@link #gcCost()} in percent to decide in favor of
+     * expanding a space by 1% of the combined size of {@link #edenSize} and {@link #promoSize}.
+     */
+    private static final double ADAPTIVE_SIZE_ESTIMATOR_MIN_TOTAL_SIZE_COST_TRADEOFF = 0.5;
     /** The effective number of most recent data points used by estimator (exponential decay). */
-    private static final int ADAPTIVE_SIZE_COST_ESTIMATORS_HISTORY_LENGTH = 12;
+    private static final double ADAPTIVE_SIZE_COST_ESTIMATORS_HISTORY_LENGTH = 12;
     /** Threshold for triggering a complete collection after repeated minor collections. */
     private static final int CONSECUTIVE_MINOR_TO_MAJOR_COLLECTION_PAUSE_TIME_RATIO = 2;
     /**
@@ -240,7 +244,7 @@ private void computeSurvivorSpaceSizeAndThreshold(boolean isSurvivorOverflow, Un
     protected void computeEdenSpaceSize(@SuppressWarnings("unused") boolean completeCollection, @SuppressWarnings("unused") GCCause cause) {
         boolean expansionReducesCost = true; // general assumption
         if (shouldUseEstimator(youngGenChangeForMinorThroughput, minorGcCost())) {
-            expansionReducesCost = expansionSignificantlyReducesCost(minorCostEstimator, edenSize);
+            expansionReducesCost = expansionSignificantlyReducesTotalCost(minorCostEstimator, edenSize, majorGcCost(), promoSize);
             /*
              * Note that if the estimator thinks expanding does not lead to significant improvement,
              * shrink so to not get stuck in a supposed optimum and to keep collecting data points.
@@ -282,15 +286,17 @@ private static boolean shouldUseEstimator(long genChangeForThroughput, double co
         return ADAPTIVE_SIZE_USE_COST_ESTIMATORS && genChangeForThroughput > ADAPTIVE_SIZE_POLICY_INITIALIZING_STEPS && cost <= ADAPTIVE_SIZE_COST_ESTIMATOR_GC_COST_LIMIT;
     }
 
-    private static boolean expansionSignificantlyReducesCost(ReciprocalLeastSquareFit estimator, UnsignedWord size) {
+    private static boolean expansionSignificantlyReducesTotalCost(ReciprocalLeastSquareFit estimator, UnsignedWord size, double otherCost, UnsignedWord otherSize) {
+        double totalSize = UnsignedUtils.toDouble(size.add(otherSize));
         double x0 = UnsignedUtils.toDouble(size);
         double deltax = (1.01 - 1) * x0;
-        if (deltax == 0) { // division by zero below
-            return false;
+        if (deltax == 0 || totalSize == 0) { // division by zero below
+            return true; // general assumption for space expansion
         }
-        double y0 = estimator.estimate(x0);
-        double y1 = y0 * (1 - 0.01 * ADAPTIVE_SIZE_ESTIMATOR_MIN_SIZE_COST_TRADEOFF);
+        double y0 = estimator.estimate(x0) + otherCost;
+        double y1 = y0 * (1 - deltax / totalSize * ADAPTIVE_SIZE_ESTIMATOR_MIN_TOTAL_SIZE_COST_TRADEOFF);
         double minSlope = (y1 - y0) / deltax;
+
         double estimatedSlope = estimator.getSlope(x0);
         return estimatedSlope <= minSlope;
     }
@@ -383,16 +389,10 @@ public void onCollectionBegin(boolean completeCollection, long requestingNanoTim
             latestMinorMutatorIntervalNanos = timer.getMeasuredNanos();
         }
 
-        // Capture the fraction of bytes in aligned chunks at the start to include all allocated
-        // (also dead) objects, because we use it to reserve aligned chunks for future allocations
-        UnsignedWord youngChunkBytes = GCImpl.getGCImpl().getAccounting().getYoungChunkBytesBefore();
-        if (youngChunkBytes.notEqual(0)) {
-            UnsignedWord youngAlignedChunkBytes = HeapImpl.getHeapImpl().getYoungGeneration().getAlignedChunkBytes();
-            avgYoungGenAlignedChunkFraction.sample(UnsignedUtils.toDouble(youngAlignedChunkBytes) / UnsignedUtils.toDouble(youngChunkBytes));
-        }
-
         timer.reset();
         timer.open(); // measure collection pause
+
+        super.onCollectionBegin(completeCollection, requestingNanoTime);
     }
 
     @Override
@@ -458,7 +458,7 @@ private void computeOldGenSpaceSize(UnsignedWord oldLive) { // compute_old_gen_f
 
         boolean expansionReducesCost = true; // general assumption
         if (shouldUseEstimator(oldGenChangeForMajorThroughput, majorGcCost())) {
-            expansionReducesCost = expansionSignificantlyReducesCost(majorCostEstimator, promoSize);
+            expansionReducesCost = expansionSignificantlyReducesTotalCost(majorCostEstimator, promoSize, minorGcCost(), edenSize);
             /*
              * Note that if the estimator thinks expanding does not lead to significant improvement,
              * shrink so to not get stuck in a supposed optimum and to keep collecting data points.

substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/AdaptiveWeightedAverage.java

@@ -39,17 +39,34 @@
 class AdaptiveWeightedAverage {
     static final int OLD_THRESHOLD = 100;
 
-    private final int weight;
+    /** @see #computeEffectiveHistoryLengthForWeight */
+    static double computeWeightForEffectiveHistoryLength(double length) {
+        assert length > 0;
+        return 100.0 * (1.0 - Math.pow(Math.E, -1.0 / length));
+    }
+
+    /**
+     * Computes the effective history length for the given weight, which is the number of data
+     * points after which the former history is discounted to 1/e, i.e., its time constant.
+     */
+    static double computeEffectiveHistoryLengthForWeight(double weight) {
+        assert weight > 0 && weight <= 100;
+        return -1.0 / Math.log(1.0 - weight / 100.0);
+    }
+
+    private final double weight;
 
     private double average;
     private long sampleCount;
     private boolean isOld;
 
-    AdaptiveWeightedAverage(int weight) {
+    /** @param weight Weight of newest sample in percent, from 0 (exclusive) to 100 (inclusive). */
+    AdaptiveWeightedAverage(double weight) {
         this(weight, 0);
     }
 
-    AdaptiveWeightedAverage(int weight, double avg) {
+    AdaptiveWeightedAverage(double weight, double avg) {
+        assert weight > 0 && weight <= 100;
         this.weight = weight;
         this.average = avg;
     }
@@ -76,16 +93,16 @@ protected double computeAdaptiveAverage(double sample, double avg) {
          * it meaningful. We'd like the first weight used to be 1, the second to be 1/2, etc until
          * we have OLD_THRESHOLD/weight samples.
          */
-        long countWeight = 0;
+        double countWeight = 0;
         if (!isOld) { // avoid division by zero if the counter wraps
-            countWeight = OLD_THRESHOLD / sampleCount;
+            countWeight = OLD_THRESHOLD / (double) sampleCount;
         }
-        long adaptiveWeight = Math.max(weight, countWeight);
+        double adaptiveWeight = Math.max(weight, countWeight);
         return expAvg(avg, sample, adaptiveWeight);
     }
 
-    private static double expAvg(double avg, double sample, long adaptiveWeight) {
-        assert adaptiveWeight <= 100 : "weight must be a percentage";
+    private static double expAvg(double avg, double sample, double adaptiveWeight) {
+        assert adaptiveWeight > 0 && adaptiveWeight <= 100 : "weight must be a percentage";
         return (100.0 - adaptiveWeight) * avg / 100.0 + adaptiveWeight * sample / 100.0;
     }
 }
@@ -103,7 +120,7 @@ class AdaptivePaddedAverage extends AdaptiveWeightedAverage {
     private double paddedAverage;
     private double deviation;
 
-    AdaptivePaddedAverage(int weight, int padding) {
+    AdaptivePaddedAverage(double weight, int padding) {
         this(weight, padding, false);
     }
 
@@ -112,7 +129,7 @@ class AdaptivePaddedAverage extends AdaptiveWeightedAverage {
      *            allowed to change. This is to prevent zero samples from drastically changing the
      *            padded average.
      */
-    AdaptivePaddedAverage(int weight, int padding, boolean noZeroDeviations) {
+    AdaptivePaddedAverage(double weight, int padding, boolean noZeroDeviations) {
         super(weight);
         this.padding = padding;
         this.noZeroDeviations = noZeroDeviations;

substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/AlignedHeapChunk.java

@@ -117,11 +117,13 @@ static UnsignedWord getCommittedObjectMemory(AlignedHeader that) {
         return HeapChunk.getEndOffset(that).subtract(getObjectsStartOffset());
     }
 
+    @Uninterruptible(reason = "Called from uninterruptible code.", mayBeInlined = true)
     public static AlignedHeader getEnclosingChunk(Object obj) {
         Pointer ptr = Word.objectToUntrackedPointer(obj);
         return getEnclosingChunkFromObjectPointer(ptr);
     }
 
+    @Uninterruptible(reason = "Called from uninterruptible code.", mayBeInlined = true)
     public static AlignedHeader getEnclosingChunkFromObjectPointer(Pointer ptr) {
         return (AlignedHeader) PointerUtils.roundDown(ptr, HeapParameters.getAlignedHeapChunkAlignment());
     }

substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/ChunkedImageHeapAllocator.java

@@ -179,7 +179,7 @@ public long getUnallocatedBytes() {
         this.position = position;
 
         /* Cache to prevent frequent lookups of the object layout from ImageSingletons. */
-        minimumObjectSize = ConfigurationValues.getObjectLayout().getMinimumObjectSize();
+        this.minimumObjectSize = ConfigurationValues.getObjectLayout().getMinImageHeapObjectSize();
     }
 
     public long getPosition() {

substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/ChunkedImageHeapPartition.java

@@ -57,7 +57,7 @@ public class ChunkedImageHeapPartition extends AbstractImageHeapPartition {
         this.hugeObjects = hugeObjects;
 
         /* Cache to prevent frequent lookups of the object layout from ImageSingletons. */
-        minimumObjectSize = ConfigurationValues.getObjectLayout().getMinimumObjectSize();
+        this.minimumObjectSize = ConfigurationValues.getObjectLayout().getMinImageHeapObjectSize();
     }
 
     boolean usesUnalignedObjects() {
@@ -134,7 +134,7 @@ private static NavigableMap<Long, Queue<ImageHeapObject>> createSortedObjectsMap
         for (ImageHeapObject obj : sorted) {
             long objSize = obj.getSize();
             if (objSize != currentObjectsSize) {
-                assert objSize > currentObjectsSize && objSize >= ConfigurationValues.getObjectLayout().getMinimumObjectSize();
+                assert objSize > currentObjectsSize && objSize >= ConfigurationValues.getObjectLayout().getMinImageHeapObjectSize();
                 currentObjectsSize = objSize;
                 currentQueue = new ArrayDeque<>();
                 map.put(currentObjectsSize, currentQueue);

substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/CollectionPolicy.java

@@ -32,6 +32,7 @@
 import com.oracle.svm.core.heap.GCCause;
 import com.oracle.svm.core.heap.PhysicalMemory;
 import com.oracle.svm.core.util.UserError;
+import com.oracle.svm.util.ReflectionUtil;
 
 /** The interface for a garbage collection policy. All sizes are in bytes. */
 public interface CollectionPolicy {
@@ -53,32 +54,38 @@ static String getInitialPolicyName() {
     @Platforms(Platform.HOSTED_ONLY.class)
     static CollectionPolicy getInitialPolicy() {
         String name = getInitialPolicyName();
+        Class<? extends CollectionPolicy> clazz = getPolicyClass(name);
+        return ReflectionUtil.newInstance(clazz);
+    }
+
+    @Platforms(Platform.HOSTED_ONLY.class)
+    static Class<? extends CollectionPolicy> getPolicyClass(String name) {
         switch (name) {
             case "Adaptive":
-                return new AdaptiveCollectionPolicy();
+                return AdaptiveCollectionPolicy.class;
             case "AggressiveShrink":
-                return new AggressiveShrinkCollectionPolicy();
+                return AggressiveShrinkCollectionPolicy.class;
             case "Proportionate":
-                return new ProportionateSpacesPolicy();
+                return ProportionateSpacesPolicy.class;
             case "BySpaceAndTime":
-                return new BasicCollectionPolicies.BySpaceAndTime();
+                return BasicCollectionPolicies.BySpaceAndTime.class;
             case "OnlyCompletely":
-                return new BasicCollectionPolicies.OnlyCompletely();
+                return BasicCollectionPolicies.OnlyCompletely.class;
             case "OnlyIncrementally":
-                return new BasicCollectionPolicies.OnlyIncrementally();
+                return BasicCollectionPolicies.OnlyIncrementally.class;
             case "NeverCollect":
-                return new BasicCollectionPolicies.NeverCollect();
+                return BasicCollectionPolicies.NeverCollect.class;
         }
         throw UserError.abort("Policy %s does not exist.", name);
     }
 
     @Platforms(Platform.HOSTED_ONLY.class)
     static int getMaxSurvivorSpaces(Integer userValue) {
         String name = getInitialPolicyName();
-        if ("Adaptive".equals(name) || "Proportionate".equals(name)) {
-            return AbstractCollectionPolicy.getMaxSurvivorSpaces(userValue);
+        if (BasicCollectionPolicies.BasicPolicy.class.isAssignableFrom(getPolicyClass(name))) {
+            return BasicCollectionPolicies.getMaxSurvivorSpaces(userValue);
         }
-        return BasicCollectionPolicies.getMaxSurvivorSpaces(userValue);
+        return AbstractCollectionPolicy.getMaxSurvivorSpaces(userValue);
     }
 
     static boolean shouldCollectYoungGenSeparately(boolean defaultValue) {

substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/GCImpl.java

@@ -196,7 +196,6 @@ private void collectOperation(CollectionVMOperationData data) {
         startCollectionOrExit();
 
         timers.resetAllExceptMutator();
-        collectionEpoch = collectionEpoch.add(1);
 
         /* Flush all TLAB chunks to eden. */
         ThreadLocalAllocation.disableAndFlushForAllThreads();
@@ -358,7 +357,7 @@ private void printGCBefore(String cause) {
         Log verboseGCLog = Log.log();
         HeapImpl heap = HeapImpl.getHeapImpl();
         sizeBefore = ((SubstrateGCOptions.PrintGC.getValue() || SerialGCOptions.PrintHeapShape.getValue()) ? getChunkBytes() : WordFactory.zero());
-        if (SubstrateGCOptions.VerboseGC.getValue() && getCollectionEpoch().equal(1)) {
+        if (SubstrateGCOptions.VerboseGC.getValue() && getCollectionEpoch().equal(0)) {
             verboseGCLog.string("[Heap policy parameters: ").newline();
             verboseGCLog.string("  YoungGenerationSize: ").unsigned(getPolicy().getMaximumYoungGenerationSize()).newline();
             verboseGCLog.string("      MaximumHeapSize: ").unsigned(getPolicy().getMaximumHeapSize()).newline();
@@ -1151,6 +1150,7 @@ private void startCollectionOrExit() {
 
     private void finishCollection() {
         assert collectionInProgress;
+        collectionEpoch = collectionEpoch.add(1);
         collectionInProgress = false;
     }