Re: [PR] [CASSANDRA-20226][trunk] Reduce contention in NativeAllocator.allocate [cassandra]

["michaelsembwever (via GitHub)" <gi...@apache.org>]

michaelsembwever commented on code in PR #4415:
URL: https://github.com/apache/cassandra/pull/4415#discussion_r2506934896


##########
src/java/org/apache/cassandra/utils/memory/NativeAllocator.java:
##########
@@ -104,30 +104,98 @@ public DecoratedKey clone(DecoratedKey key, OpOrder.Group writeOp)
     @Override
     public Cloner cloner(Group opGroup)
     {
-        return new Cloner()
-                {
-
-                    @Override
-                    public DecoratedKey clone(DecoratedKey key)
-                    {
-                        return NativeAllocator.this.clone(key, opGroup);
-                    }
-
-                    @Override
-                    public Clustering<?> clone(Clustering<?> clustering)
-                    {
-                        if (clustering != Clustering.STATIC_CLUSTERING)
-                            return new NativeClustering(NativeAllocator.this, opGroup, clustering);
-
-                        return Clustering.STATIC_CLUSTERING;
-                    }
-
-                    @Override
-                    public Cell<?> clone(Cell<?> cell)
-                    {
-                        return new NativeCell(NativeAllocator.this, opGroup, cell);
-                    }
-                };
+        return new NativeCloner(this, opGroup);
+    }
+
+    private static class NativeCloner implements Cloner, AddressBasedAllocator
+    {
+        private final NativeAllocator allocator;
+        private final Group opGroup;
+
+        private final long address;
+        private final int limit;
+        private int offset = 0;
+
+        private NativeCloner(NativeAllocator allocator, Group opGroup)
+        {
+            this(allocator, opGroup, 0);
+        }
+
+        private NativeCloner(NativeAllocator allocator, Group opGroup, int size)
+        {
+            this.allocator = allocator;
+            this.opGroup = opGroup;
+            this.limit = size;
+            this.address = size > 0 ? allocator.allocate(size, opGroup) : -1;
+        }
+
+        @Override
+        public DecoratedKey clone(DecoratedKey key)
+        {
+            return allocator.clone(key, opGroup);
+        }
+
+        @Override
+        public Clustering<?> clone(Clustering<?> clustering)
+        {
+            if (clustering != Clustering.STATIC_CLUSTERING)
+                return new NativeClustering(this, opGroup, clustering);
+
+            return Clustering.STATIC_CLUSTERING;

Review Comment:
   nit: style
   ```
   return (Clustering.STATIC_CLUSTERING == clustering) ? clustering : new NativeClustering(this, opGroup, clustering); 
   ```



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