Make RESTEasy Reactive handlers calls monomorphic

This looks ugly, but it results in better performance (cherry picked from commit 65dd4d4)
quarkusio · May 16, 2022 · fa4c991 · fa4c991
1 parent 083e22b
commit fa4c991
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diff --git a/...va/io/quarkus/resteasy/reactive/server/runtime/QuarkusResteasyReactiveRequestContext.java b/...va/io/quarkus/resteasy/reactive/server/runtime/QuarkusResteasyReactiveRequestContext.java
@@ -69,4 +69,52 @@ public void handleUnmappedException(Throwable throwable) {
     private <E extends Throwable> RuntimeException sneakyThrow(Throwable e) throws E {
         throw (E) e;
     }
+
+    /**
+     * The implementation looks like it makes no sense, but it in fact does make sense from a performance perspective.
+     * The idea is to reduce the use instances of megamorphic calls into a series of instance checks and monomorphic calls.
+     * The rationale behind this is fully explored in
+     * https://shipilev.net/blog/2015/black-magic-method-dispatch/#_cheating_the_runtime_2
+     * and this specific instance has been verified experimentally to result in better performance.
+     */
+    @Override
+    protected void invokeHandler(int pos) throws Exception {
+        var handler = handlers[pos];
+        if (handler instanceof org.jboss.resteasy.reactive.server.handlers.MatrixParamHandler) {
+            handler.handle(this);
+        } else if (handler instanceof io.quarkus.resteasy.reactive.server.runtime.security.SecurityContextOverrideHandler) {
+            handler.handle(this);
+        } else if (handler instanceof org.jboss.resteasy.reactive.server.handlers.RestInitialHandler) {
+            handler.handle(this);
+        } else if (handler instanceof org.jboss.resteasy.reactive.server.handlers.ClassRoutingHandler) {
+            handler.handle(this);
+        } else if (handler instanceof org.jboss.resteasy.reactive.server.handlers.AbortChainHandler) {
+            handler.handle(this);
+        } else if (handler instanceof org.jboss.resteasy.reactive.server.handlers.NonBlockingHandler) {
+            handler.handle(this);
+        } else if (handler instanceof org.jboss.resteasy.reactive.server.handlers.BlockingHandler) {
+            handler.handle(this);
+        } else if (handler instanceof org.jboss.resteasy.reactive.server.handlers.ResourceRequestFilterHandler) {
+            handler.handle(this);
+        } else if (handler instanceof org.jboss.resteasy.reactive.server.handlers.InputHandler) {
+            handler.handle(this);
+        } else if (handler instanceof org.jboss.resteasy.reactive.server.handlers.RequestDeserializeHandler) {
+            handler.handle(this);
+        } else if (handler instanceof org.jboss.resteasy.reactive.server.handlers.ParameterHandler) {
+            handler.handle(this);
+        } else if (handler instanceof org.jboss.resteasy.reactive.server.handlers.InstanceHandler) {
+            handler.handle(this);
+        } else if (handler instanceof org.jboss.resteasy.reactive.server.handlers.InvocationHandler) {
+            handler.handle(this);
+        } else if (handler instanceof org.jboss.resteasy.reactive.server.handlers.FixedProducesHandler) {
+            handler.handle(this);
+        } else if (handler instanceof org.jboss.resteasy.reactive.server.handlers.ResponseHandler) {
+            handler.handle(this);
+        } else if (handler instanceof org.jboss.resteasy.reactive.server.handlers.ResponseWriterHandler) {
+            handler.handle(this);
+        } else {
+            // megamorphic call for other handlers
+            handler.handle(this);
+        }
+    }
 }
diff --git a/...rc/main/java/org/jboss/resteasy/reactive/common/core/AbstractResteasyReactiveContext.java b/...rc/main/java/org/jboss/resteasy/reactive/common/core/AbstractResteasyReactiveContext.java
@@ -138,7 +138,7 @@ public void run() {
                 int pos = position;
                 position++; //increment before, as reset may reset it to zero
                 try {
-                    handlers[pos].handle((T) this);
+                    invokeHandler(pos);
                     if (suspended) {
                         synchronized (this) {
                             // as running is not volatile but instead read from inside the same monitor,
@@ -215,6 +215,10 @@ public void run() {
         }
     }
 
+    protected void invokeHandler(int pos) throws Exception {
+        handlers[pos].handle((T) this);
+    }
+
     protected void beginAsyncProcessing() {
 
     }