[GR-65896] Dynamic Heap Size Manager for Serial GC

Author: Arash Kazemi Koohbanani

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

@@ -349,7 +349,7 @@ protected SizeParameters computeSizeParameters(SizeParameters existing) {
         UnsignedWord heapSizeLimit = UnsignedUtils.max(alignDown(getHeapSizeLimit()), minAllSpaces);
 
         UnsignedWord maxHeap;
-        long optionMax = SubstrateGCOptions.MaxHeapSize.getValue();
+        long optionMax = getMaximumHeapSizeOptionValue();
         if (optionMax > 0L) {
             maxHeap = Word.unsigned(optionMax);
         } else {
@@ -418,6 +418,10 @@ protected UnsignedWord getYoungSizeLimit(UnsignedWord maxHeap) {
         return maxHeap.subtract(minSpaceSize());
     }
 
+    protected long getMaximumHeapSizeOptionValue() {
+        return SubstrateGCOptions.MaxHeapSize.getValue();
+    }
+
     protected UnsignedWord getInitialHeapSize() {
         return AbstractCollectionPolicy.INITIAL_HEAP_SIZE;
     }

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

@@ -80,6 +80,8 @@ static Class<? extends CollectionPolicy> getPolicyClass(String name) {
                 return BasicCollectionPolicies.OnlyIncrementally.class;
             case "NeverCollect":
                 return BasicCollectionPolicies.NeverCollect.class;
+            case "Dynamic":
+                return DynamicCollectionPolicy.class;
         }
         throw UserError.abort("Policy %s does not exist.", name);
     }
@@ -210,4 +212,9 @@ static boolean shouldCollectYoungGenSeparately(boolean defaultValue) {
 
     /** Called before the end of a collection, in the safepoint operation. */
     void onCollectionEnd(boolean completeCollection, GCCause cause);
+
+    /** Can be overridden to recover from OOM. */
+    default boolean isOutOfMemory(UnsignedWord usedBytes) {
+        return usedBytes.aboveThan(getMaximumHeapSize());
+    }
 }

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

@@ -0,0 +1,61 @@
+/*
+ * Copyright (c) 2025, 2025, 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.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * 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 com.oracle.svm.core.genscavenge;
+
+import org.graalvm.nativeimage.ImageSingletons;
+import org.graalvm.word.UnsignedWord;
+
+import com.oracle.svm.core.SubstrateGCOptions;
+import com.oracle.svm.core.heap.DynamicHeapSizeManager;
+
+/**
+ * This class provides the implementation of a dynamic collection policy that calls into an instance
+ * of {@link DynamicHeapSizeManager} if it exists, otherwise the implementation is equivalent to
+ * {@link AdaptiveCollectionPolicy}.
+ */
+class DynamicCollectionPolicy extends AdaptiveCollectionPolicy {
+    @Override
+    public String getName() {
+        return "dynamic";
+    }
+
+    @Override
+    protected long getMaximumHeapSizeOptionValue() {
+        if (ImageSingletons.contains(DynamicHeapSizeManager.class)) {
+            return ImageSingletons.lookup(DynamicHeapSizeManager.class).maxHeapSize().rawValue();
+        }
+
+        return SubstrateGCOptions.MaxHeapSize.getValue();
+    }
+
+    @Override
+    public boolean isOutOfMemory(UnsignedWord usedBytes) {
+        if (ImageSingletons.contains(DynamicHeapSizeManager.class)) {
+            return ImageSingletons.lookup(DynamicHeapSizeManager.class).outOfMemory(usedBytes);
+        }
+
+        return super.isOutOfMemory(usedBytes);
+    }
+}

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2013, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2013, 2025, 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
@@ -169,6 +169,9 @@ public void maybeCollectOnAllocation(UnsignedWord allocationSize) {
         } else if (getPolicy().shouldCollectOnAllocation()) {
             AllocationRequiringGCEvent.emit(getCollectionEpoch(), allocationSize);
             outOfMemory = collectWithoutAllocating(GenScavengeGCCause.OnAllocation, false);
+            if (outOfMemory) {
+                outOfMemory = getPolicy().isOutOfMemory(HeapImpl.getAccounting().getUsedBytes());
+            }
         }
         if (outOfMemory) {
             throw OutOfMemoryUtil.heapSizeExceeded();
@@ -186,7 +189,11 @@ private void collect(GCCause cause, boolean forceFullGC) {
         if (!hasNeverCollectPolicy()) {
             boolean outOfMemory = collectWithoutAllocating(cause, forceFullGC);
             if (outOfMemory) {
-                throw OutOfMemoryUtil.heapSizeExceeded();
+                if (getPolicy().isOutOfMemory(HeapImpl.getAccounting().getUsedBytes())) {
+                    throw OutOfMemoryUtil.heapSizeExceeded();
+                } else {
+                    GCImpl.getPolicy().updateSizeParameters();
+                }
             }
         }
     }

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

@@ -269,7 +269,7 @@ public static Object slowPathNewArrayLikeObject(Word objectHeader, int length, b
          * object is allocated and survives.
          */
         GCImpl.getPolicy().ensureSizeParametersInitialized();
-        if (size.aboveOrEqual(GCImpl.getPolicy().getMaximumHeapSize()) && !GCImpl.shouldIgnoreOutOfMemory()) {
+        if (GCImpl.getPolicy().isOutOfMemory(size) && !GCImpl.shouldIgnoreOutOfMemory()) {
             OutOfMemoryError outOfMemoryError = new OutOfMemoryError("Array allocation too large.");
             throw OutOfMemoryUtil.reportOutOfMemoryError(outOfMemoryError);
         }

substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/heap/DynamicHeapSizeManager.java

@@ -0,0 +1,54 @@
+/*
+ * Copyright (c) 2025, 2025, 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.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * 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 com.oracle.svm.core.heap;
+
+import static com.oracle.svm.core.heap.RestrictHeapAccess.Access.NO_ALLOCATION;
+
+import org.graalvm.word.UnsignedWord;
+
+import com.oracle.svm.core.SubstrateGCOptions;
+
+/**
+ * This interface defines the functions needed to implement a dynamic heap size manager, where the
+ * Java heap size can be changed at runtime.
+ */
+public interface DynamicHeapSizeManager {
+    /**
+     * Retrieves the current max heap size, overrides {@link SubstrateGCOptions#MaxHeapSize}.
+     *
+     * @return max heap size
+     */
+    @RestrictHeapAccess(access = NO_ALLOCATION, reason = "Called from allocation-free code paths.")
+    UnsignedWord maxHeapSize();
+
+    /**
+     * In case of OOM, try to request additional memory.
+     *
+     * @param bytes memory required
+     * @return true if out of memory, false if max heap size was increased
+     */
+    @RestrictHeapAccess(access = NO_ALLOCATION, reason = "Called from allocation-free code paths.")
+    boolean outOfMemory(UnsignedWord bytes);
+}

substratevm/src/com.oracle.svm.core/src/com/oracle/svm/core/heap/dump/HeapDumpSupportImpl.java

@@ -201,13 +201,16 @@ private class HeapDumpOperation extends NativeVMOperation {
         }
 
         @Override
-        @RestrictHeapAccess(access = NO_ALLOCATION, reason = "Heap dumping must not allocate.")
         protected void operate(NativeVMOperationData d) {
             HeapDumpVMOperationData data = (HeapDumpVMOperationData) d;
             if (data.getGCBefore()) {
                 Heap.getHeap().getGC().collectCompletely(GCCause.HeapDump);
             }
+            dumpHeap(data);
+        }
 
+        @RestrictHeapAccess(access = NO_ALLOCATION, reason = "Heap dumping must not allocate.")
+        private void dumpHeap(HeapDumpVMOperationData data) {
             try {
                 boolean success = writer.dumpHeap(data.getRawFileDescriptor());
                 data.setSuccess(success);