Various cleanups and fixes for the parallel GC.

Author: christianhaeubl

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

@@ -210,17 +210,15 @@ private Pointer allocateMemoryParallel(UnsignedWord objectSize) {
             }
         }
         /* Slow-path: try allocating a new chunk for the requested memory. */
-        return allocateInNewChunkParallel(oldChunk, objectSize);
+        return allocateInNewChunkParallel(objectSize);
     }
 
     @Uninterruptible(reason = "Called from uninterruptible code.", mayBeInlined = true)
-    private Pointer allocateInNewChunkParallel(AlignedHeapChunk.AlignedHeader oldChunk, UnsignedWord objectSize) {
+    private Pointer allocateInNewChunkParallel(UnsignedWord objectSize) {
         AlignedHeapChunk.AlignedHeader newChunk;
         ParallelGC.singleton().getMutex().lockNoTransitionUnspecifiedOwner();
         try {
-            if (oldChunk.isNonNull()) {
-                ParallelGC.singleton().pushAllocChunk(oldChunk);
-            }
+            ParallelGC.singleton().pushAllocChunk();
             newChunk = requestAlignedHeapChunk();
         } finally {
             ParallelGC.singleton().getMutex().unlockNoTransitionUnspecifiedOwner();
@@ -361,7 +359,7 @@ private void extractUnalignedHeapChunk(UnalignedHeapChunk.UnalignedHeader uChunk
     private static boolean verifyMutualExclusionForAppendChunk() {
         return !SubstrateOptions.MultiThreaded.getValue() ||
                         VMThreads.ownsThreadMutex(true) ||
-                        ParallelGC.isEnabled() && VMOperation.isGCInProgress() && ParallelGC.singleton().isInParallelPhase() && ParallelGC.singleton().getMutex().isOwner();
+                        ParallelGC.isEnabled() && VMOperation.isGCInProgress() && ParallelGC.singleton().isInParallelPhase() && ParallelGC.singleton().getMutex().isOwner(true);
     }
 
     @Uninterruptible(reason = "Called from uninterruptible code.", mayBeInlined = true)

substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/jvmstat/SerialGCPerfData.java

@@ -34,6 +34,7 @@
 import com.oracle.svm.core.genscavenge.HeapAccounting;
 import com.oracle.svm.core.genscavenge.HeapImpl;
 import com.oracle.svm.core.genscavenge.HeapParameters;
+import com.oracle.svm.core.genscavenge.parallel.ParallelGC;
 import com.oracle.svm.core.jvmstat.PerfDataHolder;
 import com.oracle.svm.core.jvmstat.PerfLongConstant;
 import com.oracle.svm.core.jvmstat.PerfLongCounter;
@@ -45,6 +46,7 @@
 /**
  * Performance data for our serial GC.
  */
+// TODO (chaeubl): rename this class
 public class SerialGCPerfData implements PerfDataHolder {
     private final PerfDataGCPolicy gcPolicy;
     private final PerfDataCollector youngCollector;
@@ -78,7 +80,9 @@ public void allocate() {
         gcPolicy.allocate();
 
         youngCollector.allocate("Serial young collection pauses");
-        oldCollector.allocate("Serial full collection pauses");
+
+        String oldCollectorName = ParallelGC.isEnabled() ? "Parallel" : "Serial";
+        oldCollector.allocate(oldCollectorName + " full collection pauses");
 
         youngGen.allocate("young");
         youngGen.spaces[0].allocate("eden");

substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/parallel/ChunkBuffer.java renamed to substratevm/src/com.oracle.svm.core.genscavenge/src/com/oracle/svm/core/genscavenge/parallel/ChunkQueue.java

@@ -40,14 +40,15 @@
 import com.oracle.svm.core.util.VMError;
 
 /**
- * Synchronized buffer that stores pointers into "grey" heap chunks that need to be scanned. Note
- * that the pointers don't necessarily point to the beginning of a chunk.
+ * A queue that stores pointers into "grey" heap chunks that need to be scanned. Note that the
+ * pointers don't necessarily point to the beginning of a chunk. GC workers threads may only access
+ * the queue if they hold {@link ParallelGC#getMutex()}.
  */
-public class ChunkBuffer {
+public class ChunkQueue {
     private static final int INITIAL_SIZE = 1024 * wordSize();
 
     private Pointer buffer;
-    private int size = INITIAL_SIZE;
+    private int size;
     private int top;
 
     @Fold
@@ -56,42 +57,39 @@ static int wordSize() {
     }
 
     @Platforms(Platform.HOSTED_ONLY.class)
-    ChunkBuffer() {
+    ChunkQueue() {
     }
 
     @Uninterruptible(reason = "Called from uninterruptible code.", mayBeInlined = true)
     public void initialize() {
+        assert top == 0 && size == 0 && buffer.isNull();
+        top = 0;
+        size = INITIAL_SIZE;
         buffer = ImageSingletons.lookup(UnmanagedMemorySupport.class).malloc(WordFactory.unsigned(size));
-        VMError.guarantee(buffer.isNonNull());
+        VMError.guarantee(buffer.isNonNull(), "Failed to allocate native memory for the ChunkBuffer.");
     }
 
     @Uninterruptible(reason = "Called from uninterruptible code.", mayBeInlined = true)
     void push(Pointer ptr) {
-        assert !ParallelGC.singleton().isInParallelPhase() && VMThreads.ownsThreadMutex() || ParallelGC.singleton().getMutex().hasOwner();
+        assert !ParallelGC.singleton().isInParallelPhase() && VMThreads.ownsThreadMutex() || ParallelGC.singleton().isInParallelPhase() && ParallelGC.singleton().getMutex().isOwner(true);
         if (top >= size) {
             size *= 2;
             assert top < size;
             buffer = ImageSingletons.lookup(UnmanagedMemorySupport.class).realloc(buffer, WordFactory.unsigned(size));
-            VMError.guarantee(buffer.isNonNull());
+            VMError.guarantee(buffer.isNonNull(), "Failed to allocate native memory for the ChunkBuffer.");
         }
         buffer.writeWord(top, ptr);
         top += wordSize();
     }
 
     @Uninterruptible(reason = "Called from uninterruptible code.", mayBeInlined = true)
     Pointer pop() {
-        assert ParallelGC.singleton().isInParallelPhase();
-        ParallelGC.singleton().getMutex().lockNoTransitionUnspecifiedOwner();
-        try {
-            if (top > 0) {
-                top -= wordSize();
-                return buffer.readWord(top);
-            } else {
-                return WordFactory.nullPointer();
-            }
-        } finally {
-            ParallelGC.singleton().getMutex().unlockNoTransitionUnspecifiedOwner();
+        assert ParallelGC.singleton().isInParallelPhase() && ParallelGC.singleton().getMutex().isOwner(true);
+        if (top > 0) {
+            top -= wordSize();
+            return buffer.readWord(top);
         }
+        return WordFactory.nullPointer();
     }
 
     @Uninterruptible(reason = "Called from uninterruptible code.", mayBeInlined = true)
@@ -101,7 +99,10 @@ boolean isEmpty() {
     }
 
     @Uninterruptible(reason = "Called from uninterruptible code.", mayBeInlined = true)
-    void release() {
+    void teardown() {
         ImageSingletons.lookup(UnmanagedMemorySupport.class).free(buffer);
+        buffer = WordFactory.nullPointer();
+        size = 0;
+        top = 0;
     }
 }