[GR-48343] [GR-48359] Add support for JFR events AllocationRequiringGC and SystemGC.

PullRequest: graal/15416

Author: christianhaeubl

substratevm/CHANGELOG.md

@@ -4,6 +4,7 @@ This changelog summarizes major changes to GraalVM Native Image.
 
 ## GraalVM for JDK 22 (Internal Version 24.0.0)
 * (GR-48304) Red Hat added support for the JFR event ThreadAllocationStatistics.
+* (GR-48343) Red Hat added support for the JFR events AllocationRequiringGC and SystemGC.
 
 ## GraalVM for JDK 21 (Internal Version 23.1.0)
 * (GR-35746) Lower the default aligned chunk size from 1 MB to 512 KB for the serial and epsilon GCs, reducing memory usage and image size in many cases.

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

@@ -35,7 +35,6 @@
 
 import com.oracle.svm.core.SubstrateGCOptions;
 import com.oracle.svm.core.Uninterruptible;
-import com.oracle.svm.core.heap.GCCause;
 import com.oracle.svm.core.heap.PhysicalMemory;
 import com.oracle.svm.core.heap.ReferenceAccess;
 import com.oracle.svm.core.jdk.UninterruptibleUtils;
@@ -96,8 +95,9 @@ public boolean shouldCollectOnAllocation() {
     }
 
     @Override
-    public boolean shouldCollectOnRequest(GCCause cause, boolean fullGC) {
-        return cause == GCCause.JavaLangSystemGC && !SubstrateGCOptions.DisableExplicitGC.getValue();
+    public boolean shouldCollectOnHint(boolean fullGC) {
+        /* Collection hints are not supported. */
+        return false;
     }
 
     @Fold

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

@@ -63,8 +63,9 @@ public boolean shouldCollectOnAllocation() {
         }
 
         @Override
-        public boolean shouldCollectOnRequest(GCCause cause, boolean fullGC) {
-            return cause == GCCause.JavaLangSystemGC && !SubstrateGCOptions.DisableExplicitGC.getValue();
+        public boolean shouldCollectOnHint(boolean fullGC) {
+            /* Collection hints are not supported. */
+            return false;
         }
 
         @Override

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

@@ -122,11 +122,10 @@ static boolean shouldCollectYoungGenSeparately(boolean defaultValue) {
     boolean shouldCollectOnAllocation();
 
     /**
-     * Return true if a user-requested GC (e.g., call to {@link System#gc()} or
-     * {@link org.graalvm.compiler.serviceprovider.GraalServices#notifyLowMemoryPoint(boolean)})
-     * should be performed.
+     * Called when an application provides a hint to the GC that it might be a good time to do a
+     * collection. Returns true if the GC decides to do a collection.
      */
-    boolean shouldCollectOnRequest(GCCause cause, boolean fullGC);
+    boolean shouldCollectOnHint(boolean fullGC);
 
     /**
      * At a safepoint, decides whether to do a complete collection (returning {@code true}) or an

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

@@ -78,6 +78,7 @@ public long getIncrementalCollectionTotalNanos() {
         return incrementalCollectionTotalNanos;
     }
 
+    @Uninterruptible(reason = "Called from uninterruptible code.", mayBeInlined = true)
     public long getCompleteCollectionCount() {
         return completeCollectionCount;
     }

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

@@ -81,6 +81,7 @@
 import com.oracle.svm.core.jdk.RuntimeSupport;
 import com.oracle.svm.core.jfr.JfrGCWhen;
 import com.oracle.svm.core.jfr.JfrTicks;
+import com.oracle.svm.core.jfr.events.AllocationRequiringGCEvent;
 import com.oracle.svm.core.log.Log;
 import com.oracle.svm.core.os.CommittedMemoryProvider;
 import com.oracle.svm.core.snippets.ImplicitExceptions;
@@ -144,12 +145,13 @@ public void collect(GCCause cause) {
         collect(cause, false);
     }
 
-    public void maybeCollectOnAllocation() {
+    public void maybeCollectOnAllocation(UnsignedWord allocationSize) {
         boolean outOfMemory = false;
         if (hasNeverCollectPolicy()) {
             UnsignedWord edenUsed = HeapImpl.getAccounting().getEdenUsedBytes();
             outOfMemory = edenUsed.aboveThan(GCImpl.getPolicy().getMaximumHeapSize());
         } else if (getPolicy().shouldCollectOnAllocation()) {
+            AllocationRequiringGCEvent.emit(getCollectionEpoch(), allocationSize);
             outOfMemory = collectWithoutAllocating(GenScavengeGCCause.OnAllocation, false);
         }
         if (outOfMemory) {
@@ -158,9 +160,9 @@ public void maybeCollectOnAllocation() {
     }
 
     @Override
-    public void maybeCauseUserRequestedCollection(GCCause cause, boolean fullGC) {
-        if (policy.shouldCollectOnRequest(cause, fullGC)) {
-            collect(cause, fullGC);
+    public void collectionHint(boolean fullGC) {
+        if (policy.shouldCollectOnHint(fullGC)) {
+            collect(GCCause.HintedGC, fullGC);
         }
     }
 
@@ -183,6 +185,7 @@ boolean collectWithoutAllocating(GCCause cause, boolean forceFullGC) {
         UnmanagedMemoryUtil.fill((Pointer) data, WordFactory.unsigned(size), (byte) 0);
         data.setCauseId(cause.getId());
         data.setRequestingEpoch(getCollectionEpoch());
+        data.setCompleteCollectionCount(GCImpl.getAccounting().getCompleteCollectionCount());
         data.setRequestingNanoTime(System.nanoTime());
         data.setForceFullGC(forceFullGC);
         enqueueCollectOperation(data);
@@ -197,7 +200,8 @@ private void enqueueCollectOperation(CollectionVMOperationData data) {
     /** The body of the VMOperation to do the collection. */
     private void collectOperation(CollectionVMOperationData data) {
         assert VMOperation.isGCInProgress();
-        assert getCollectionEpoch().equal(data.getRequestingEpoch());
+        assert getCollectionEpoch().equal(data.getRequestingEpoch()) ||
+                        data.getForceFullGC() && GCImpl.getAccounting().getCompleteCollectionCount() == data.getCompleteCollectionCount() : "unnecessary GC?";
 
         timers.mutator.closeAt(data.getRequestingNanoTime());
         timers.resetAllExceptMutator();
@@ -1205,7 +1209,12 @@ private static void collect(CollectionVMOperationData data) {
         @Override
         protected boolean hasWork(NativeVMOperationData data) {
             CollectionVMOperationData d = (CollectionVMOperationData) data;
-            return HeapImpl.getGCImpl().getCollectionEpoch().equal(d.getRequestingEpoch());
+            if (d.getForceFullGC()) {
+                /* Skip if another full GC happened in the meanwhile. */
+                return GCImpl.getAccounting().getCompleteCollectionCount() == d.getCompleteCollectionCount();
+            }
+            /* Skip if any other GC happened in the meanwhile. */
+            return GCImpl.getGCImpl().getCollectionEpoch().equal(d.getRequestingEpoch());
         }
     }
 
@@ -1235,6 +1244,12 @@ private interface CollectionVMOperationData extends NativeVMOperationData {
         @RawField
         void setForceFullGC(boolean value);
 
+        @RawField
+        long getCompleteCollectionCount();
+
+        @RawField
+        void setCompleteCollectionCount(long value);
+
         @RawField
         boolean getOutOfMemory();
 

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

@@ -48,6 +48,7 @@
 import com.oracle.svm.core.SubstrateDiagnostics.DiagnosticThunk;
 import com.oracle.svm.core.SubstrateDiagnostics.DiagnosticThunkRegistry;
 import com.oracle.svm.core.SubstrateDiagnostics.ErrorContext;
+import com.oracle.svm.core.SubstrateGCOptions;
 import com.oracle.svm.core.SubstrateOptions;
 import com.oracle.svm.core.SubstrateUtil;
 import com.oracle.svm.core.Uninterruptible;
@@ -73,6 +74,8 @@
 import com.oracle.svm.core.heap.RuntimeCodeInfoGCSupport;
 import com.oracle.svm.core.hub.DynamicHub;
 import com.oracle.svm.core.jdk.UninterruptibleUtils.AtomicReference;
+import com.oracle.svm.core.jfr.JfrTicks;
+import com.oracle.svm.core.jfr.events.SystemGCEvent;
 import com.oracle.svm.core.locks.VMCondition;
 import com.oracle.svm.core.locks.VMMutex;
 import com.oracle.svm.core.log.Log;
@@ -941,6 +944,10 @@ private long maxMemory() {
 
     @Substitute
     private void gc() {
-        GCImpl.getGCImpl().maybeCauseUserRequestedCollection(GCCause.JavaLangSystemGC, true);
+        if (!SubstrateGCOptions.DisableExplicitGC.getValue()) {
+            long startTicks = JfrTicks.elapsedTicks();
+            GCImpl.getGCImpl().collectCompletely(GCCause.JavaLangSystemGC);
+            SystemGCEvent.emit(startTicks, false);
+        }
     }
 }

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

@@ -73,20 +73,18 @@ public static final class Options {
      * size is lower but the hinted GC is more often.
      */
     @Override
-    public boolean shouldCollectOnRequest(GCCause cause, boolean fullGC) {
-        if (cause == GCCause.HintedGC) {
-            guaranteeSizeParametersInitialized();
-            UnsignedWord edenUsedBytes = HeapImpl.getAccounting().getEdenUsedBytes();
-            if (fullGC) {
-                // For full GC request, we slightly lower the threshold to increase their
-                // probability to be performed, as they are supposed to be issued at the lowest
-                // memory usage point.
-                edenUsedBytes = edenUsedBytes.add(FULL_GC_BONUS);
-            }
-            return edenUsedBytes.aboveOrEqual(WordFactory.unsigned(Options.ExpectedEdenSize.getValue())) ||
-                            (UnsignedUtils.toDouble(edenUsedBytes) / UnsignedUtils.toDouble(edenSize) >= Options.UsedEdenProportionThreshold.getValue());
+    public boolean shouldCollectOnHint(boolean fullGC) {
+        guaranteeSizeParametersInitialized();
+        UnsignedWord edenUsedBytes = HeapImpl.getAccounting().getEdenUsedBytes();
+        if (fullGC) {
+            /*
+             * For full GC request, we slightly lower the threshold to increase their probability to
+             * be performed, as they are supposed to be issued at the lowest memory usage point.
+             */
+            edenUsedBytes = edenUsedBytes.add(FULL_GC_BONUS);
         }
-        return super.shouldCollectOnRequest(cause, fullGC);
+        return edenUsedBytes.aboveOrEqual(WordFactory.unsigned(Options.ExpectedEdenSize.getValue())) ||
+                        (UnsignedUtils.toDouble(edenUsedBytes) / UnsignedUtils.toDouble(edenSize) >= Options.UsedEdenProportionThreshold.getValue());
     }
 
     @Override

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

@@ -230,14 +230,15 @@ private static Object slowPathNewInstance(Word objectHeader) {
     private static Object slowPathNewInstanceWithoutAllocating(DynamicHub hub) {
         DeoptTester.disableDeoptTesting();
         long startTicks = JfrTicks.elapsedTicks();
+        UnsignedWord size = LayoutEncoding.getPureInstanceAllocationSize(hub.getLayoutEncoding());
         try {
             HeapImpl.exitIfAllocationDisallowed("ThreadLocalAllocation.slowPathNewInstanceWithoutAllocating", DynamicHub.toClass(hub).getName());
-            GCImpl.getGCImpl().maybeCollectOnAllocation();
+            GCImpl.getGCImpl().maybeCollectOnAllocation(size);
 
             AlignedHeader newTlab = HeapImpl.getChunkProvider().produceAlignedChunk();
-            return allocateInstanceInNewTlab(hub, newTlab);
+            return allocateInstanceInNewTlab(hub, size, newTlab);
         } finally {
-            ObjectAllocationInNewTLABEvent.emit(startTicks, hub, LayoutEncoding.getPureInstanceAllocationSize(hub.getLayoutEncoding()), HeapParameters.getAlignedHeapChunkSize());
+            ObjectAllocationInNewTLABEvent.emit(startTicks, hub, size, HeapParameters.getAlignedHeapChunkSize());
             DeoptTester.enableDeoptTesting();
         }
     }
@@ -296,7 +297,7 @@ private static Object slowPathNewArrayLikeObject0(DynamicHub hub, int length, Un
         UnsignedWord tlabSize = HeapParameters.getAlignedHeapChunkSize();
         try {
             HeapImpl.exitIfAllocationDisallowed("ThreadLocalAllocation.slowPathNewArrayOrPodWithoutAllocating", DynamicHub.toClass(hub).getName());
-            GCImpl.getGCImpl().maybeCollectOnAllocation();
+            GCImpl.getGCImpl().maybeCollectOnAllocation(size);
 
             if (size.aboveOrEqual(HeapParameters.getLargeArrayThreshold())) {
                 /* Large arrays go into their own unaligned chunk. */
@@ -305,10 +306,12 @@ private static Object slowPathNewArrayLikeObject0(DynamicHub hub, int length, Un
                 tlabSize = UnalignedHeapChunk.getChunkSizeForObject(size);
                 return allocateLargeArrayLikeObjectInNewTlab(hub, length, size, newTlabChunk, needsZeroing, podReferenceMap);
             }
-            /* Small arrays go into the regular aligned chunk. */
 
-            // We might have allocated in the caller and acquired a TLAB with enough space already
-            // (but we need to check in an uninterruptible method to be safe)
+            /*
+             * Small arrays go into the regular aligned chunk. We might have allocated in the caller
+             * and acquired a TLAB with enough space already (but we need to check in an
+             * uninterruptible method to be safe).
+             */
             Object array = allocateSmallArrayLikeObjectInCurrentTlab(hub, length, size, podReferenceMap);
             if (array == null) { // We need a new chunk.
                 AlignedHeader newTlabChunk = HeapImpl.getChunkProvider().produceAlignedChunk();
@@ -322,8 +325,8 @@ private static Object slowPathNewArrayLikeObject0(DynamicHub hub, int length, Un
     }
 
     @Uninterruptible(reason = "Holds uninitialized memory.")
-    private static Object allocateInstanceInNewTlab(DynamicHub hub, AlignedHeader newTlabChunk) {
-        UnsignedWord size = LayoutEncoding.getPureInstanceAllocationSize(hub.getLayoutEncoding());
+    private static Object allocateInstanceInNewTlab(DynamicHub hub, UnsignedWord size, AlignedHeader newTlabChunk) {
+        assert size.equal(LayoutEncoding.getPureInstanceAllocationSize(hub.getLayoutEncoding()));
         Pointer memory = allocateRawMemoryInNewTlab(size, newTlabChunk);
         return FormatObjectNode.formatObject(memory, DynamicHub.toClass(hub), false, FillContent.WITH_ZEROES, true);
     }

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

@@ -31,13 +31,15 @@ public interface GC {
     /** Cause a full collection. */
     void collectCompletely(GCCause cause);
 
+    /**
+     * Notify the GC that it might be a good time to do a collection. The final decision is up to
+     * the GC and its policy.
+     */
+    void collectionHint(boolean fullGC);
+
     /** Human-readable name. */
     String getName();
 
     /** Human-readable default heap size. */
     String getDefaultMaxHeapSize();
-
-    /** Issue an optional GC request. */
-    default void maybeCauseUserRequestedCollection(@SuppressWarnings("unused") GCCause cause, @SuppressWarnings("unused") boolean fullGC) {
-    }
 }