Stabilize secondary_super_cache in server code

jetty-core/jetty-io/src/main/java/org/eclipse/jetty/io/FillInterest.java

@@ -19,7 +19,6 @@
 import java.util.concurrent.atomic.AtomicReference;
 
 import org.eclipse.jetty.util.Callback;
-import org.eclipse.jetty.util.thread.Invocable;
 import org.eclipse.jetty.util.thread.Invocable.InvocationType;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -116,7 +115,8 @@ public boolean isInterested()
     public InvocationType getCallbackInvocationType()
     {
         Callback callback = _interested.get();
-        return Invocable.getInvocationType(callback);
+        // Identical to Invocable.getInvocationType(callback) except that the cast is costly here.
+        return callback == null ? InvocationType.BLOCKING : callback.getInvocationType();
     }
 
     /**

jetty-core/jetty-server/src/main/java/org/eclipse/jetty/server/Request.java

@@ -25,7 +25,9 @@
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Locale;
+import java.util.Map;
 import java.util.Objects;
+import java.util.Set;
 import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.TimeoutException;
 import java.util.function.Consumer;
@@ -714,11 +716,21 @@ default InvocationType getInvocationType()
     /**
      * <p>A wrapper for {@code Request} instances.</p>
      */
-    class Wrapper extends Attributes.Wrapper implements Request
+    class Wrapper implements Request, Attributes
     {
+        /**
+         * Implementation note: {@link Request.Wrapper} does not extend from {@link Attributes.Wrapper}
+         * as {@link #getWrapped()} would either need to be implemented as {@code return (Request)getWrapped()}
+         * which would require a cast from one interface type to another, spoiling the JVM's
+         * {@code secondary_super_cache}, or by storing the same {@code _wrapped} object in two fields
+         * (one in {@link Attributes.Wrapper} as type {@link Attributes} and one in {@link Request.Wrapper} as
+         * type {@link Request}) to save the costly cast from interface type to another.
+         */
+        private final Request _wrapped;
+
         public Wrapper(Request wrapped)
         {
-            super(wrapped);
+            _wrapped = Objects.requireNonNull(wrapped);
         }
 
         @Override
@@ -854,9 +866,44 @@ public Session getSession(boolean create)
         }
 
         @Override
+        public Object removeAttribute(String name)
+        {
+            return getWrapped().removeAttribute(name);
+        }
+
+        @Override
+        public Object setAttribute(String name, Object attribute)
+        {
+            return getWrapped().setAttribute(name, attribute);
+        }
+
+        @Override
+        public Object getAttribute(String name)
+        {
+            return getWrapped().getAttribute(name);
+        }
+
+        @Override
+        public Set<String> getAttributeNameSet()
+        {
+            return getWrapped().getAttributeNameSet();
+        }
+
+        @Override
+        public Map<String, Object> asAttributeMap()
+        {
+            return getWrapped().asAttributeMap();
+        }
+
+        @Override
+        public void clearAttributes()
+        {
+            getWrapped().clearAttributes();
+        }
+
         public Request getWrapped()
         {
-            return (Request)super.getWrapped();
+            return _wrapped;
         }
     }