GROOVY-10307: add JMH benchmarks for Grails-like invokedynamic pain points

Add 43 JMH benchmarks across 4 files targeting the metaclass invalidation
patterns that cause performance regression in Grails applications under
invokedynamic. These complement the general-purpose benchmarks from apache#2381
by exercising the specific dynamic dispatch patterns identified in apache#2374
and apache#2377.

New benchmark files:

MetaclassChangeBench (11 benchmarks)
- ExpandoMetaClass method addition during method dispatch
- Metaclass replacement cycles
- Multi-class invalidation cascade (change on ServiceA invalidates ServiceB/C)
- Burst-then-steady-state (simulates Grails startup then request handling)
- Property access and closure dispatch under metaclass churn

CategoryBench (10 benchmarks)
- use(Category) blocks inside vs outside loops
- Nested and simultaneous multi-category scopes
- Collateral invalidation damage on non-category call sites
- Category method shadowing existing methods

DynamicDispatchBench (12 benchmarks)
- methodMissing with single/rotating names (dynamic finders)
- propertyMissing read/write (Grails params/session)
- GroovyInterceptable invokeMethod interception (transactional services)
- ExpandoMetaClass-injected method calls mixed with real methods
- def-typed monomorphic and polymorphic dispatch

GrailsLikePatternsBench (10 benchmarks)
- Service chain: validation, CRUD, collection processing
- Controller action: param binding, service call, model/view rendering
- Domain validation with dynamic property access (this."$field")
- Configuration DSL with nested @DelegatesTo closures
- Markup builder with nested tag/closure rendering
- Full request cycle simulation with and without metaclass churn

Run with: ./gradlew perf:jmh -PbenchInclude=perf

Author: jamesfredley

subprojects/performance/src/jmh/groovy/org/apache/groovy/perf/CategoryBench.groovy

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+/*
+ *  Licensed to the Apache Software Foundation (ASF) under one
+ *  or more contributor license agreements.  See the NOTICE file
+ *  distributed with this work for additional information
+ *  regarding copyright ownership.  The ASF licenses this file
+ *  to you under the Apache License, Version 2.0 (the
+ *  "License"); you may not use this file except in compliance
+ *  with the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing,
+ *  software distributed under the License is distributed on an
+ *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ *  KIND, either express or implied.  See the License for the
+ *  specific language governing permissions and limitations
+ *  under the License.
+ */
+package org.apache.groovy.perf
+
+import org.openjdk.jmh.annotations.*
+import org.openjdk.jmh.infra.Blackhole
+
+import java.util.concurrent.TimeUnit
+
+/**
+ * Tests the performance of Groovy category usage patterns. Categories
+ * are a key metaclass mechanism used heavily in Grails and other Groovy
+ * frameworks: each {@code use(Category)} block temporarily modifies
+ * method dispatch for the current thread.
+ *
+ * Every entry into and exit from a {@code use} block triggers
+ * {@code invalidateSwitchPoints()}, causing global SwitchPoint
+ * invalidation. In tight loops or frequently called code, this
+ * creates significant overhead as all invokedynamic call sites must
+ * re-link after each category scope change.
+ *
+ * Grails uses categories for date utilities, collection enhancements,
+ * validation helpers, and domain class extensions.
+ */
+@Warmup(iterations = 3, time = 2, timeUnit = TimeUnit.SECONDS)
+@Measurement(iterations = 5, time = 2, timeUnit = TimeUnit.SECONDS)
+@Fork(2)
+@BenchmarkMode(Mode.AverageTime)
+@OutputTimeUnit(TimeUnit.MILLISECONDS)
+@State(Scope.Thread)
+class CategoryBench {
+    static final int ITERATIONS = 100_000
+
+    // Category that adds methods to String
+    static class StringCategory {
+        static String reverse(String self) {
+            self.reverse()
+        }
+
+        static String shout(String self) {
+            self.toUpperCase() + '!'
+        }
+
+        static boolean isPalindrome(String self) {
+            self == self.reverse()
+        }
+    }
+
+    // Category that adds methods to Integer
+    static class MathCategory {
+        static int doubled(Integer self) {
+            self * 2
+        }
+
+        static boolean isEven(Integer self) {
+            self % 2 == 0
+        }
+
+        static int factorial(Integer self) {
+            (1..self).inject(1) { acc, val -> acc * val }
+        }
+    }
+
+    // Category that adds methods to List
+    static class CollectionCategory {
+        static int sumAll(List self) {
+            self.sum() ?: 0
+        }
+
+        static List doubled(List self) {
+            self.collect { it * 2 }
+        }
+    }
+
+    String testString
+    List<Integer> testList
+
+    @Setup(Level.Trial)
+    void setup() {
+        testString = "hello"
+        testList = (1..10).toList()
+    }
+
+    // ===== BASELINE (no categories) =====
+
+    /**
+     * Baseline: direct method calls without any category usage.
+     * Establishes the cost of normal method dispatch for comparison.
+     */
+    @Benchmark
+    void baselineDirectCalls(Blackhole bh) {
+        int sum = 0
+        for (int i = 0; i < ITERATIONS; i++) {
+            sum += testString.length()
+        }
+        bh.consume(sum)
+    }
+
+    // ===== SINGLE CATEGORY =====
+
+    /**
+     * Single category block wrapping many calls. The category scope
+     * is entered once and all calls happen inside it. This is the
+     * most efficient category usage pattern - one enter/exit pair
+     * for many method invocations.
+     */
+    @Benchmark
+    void singleCategoryWrappingLoop(Blackhole bh) {
+        int sum = 0
+        use(StringCategory) {
+            for (int i = 0; i < ITERATIONS; i++) {
+                sum += testString.shout().length()
+            }
+        }
+        bh.consume(sum)
+    }
+
+    /**
+     * Category block entered on every iteration - the worst case.
+     * Each iteration enters and exits the category scope, triggering
+     * two SwitchPoint invalidations per iteration.
+     *
+     * This pattern appears in Grails when category-enhanced methods
+     * are called from within request-scoped code that repeatedly
+     * enters category scope.
+     */
+    @Benchmark
+    void categoryInLoop(Blackhole bh) {
+        int sum = 0
+        for (int i = 0; i < ITERATIONS; i++) {
+            use(StringCategory) {
+                sum += testString.shout().length()
+            }
+        }
+        bh.consume(sum)
+    }
+
+    /**
+     * Category enter/exit at moderate frequency - every 100 calls.
+     * Simulates code where category scope is entered per-batch
+     * rather than per-call.
+     */
+    @Benchmark
+    void categoryPerBatch(Blackhole bh) {
+        int sum = 0
+        for (int i = 0; i < ITERATIONS / 100; i++) {
+            use(StringCategory) {
+                for (int j = 0; j < 100; j++) {
+                    sum += testString.shout().length()
+                }
+            }
+        }
+        bh.consume(sum)
+    }
+
+    // ===== NESTED CATEGORIES =====
+
+    /**
+     * Nested category scopes - multiple categories active at once.
+     * Each nesting level adds another enter/exit invalidation pair.
+     * Grails applications often have multiple category layers active
+     * simultaneously (e.g., date utilities inside collection utilities
+     * inside validation helpers).
+     */
+    @Benchmark
+    void nestedCategories(Blackhole bh) {
+        int sum = 0
+        for (int i = 0; i < ITERATIONS; i++) {
+            use(StringCategory) {
+                use(MathCategory) {
+                    sum += testString.shout().length() + i.doubled()
+                }
+            }
+        }
+        bh.consume(sum)
+    }
+
+    /**
+     * Nested categories with the outer scope wrapping the loop.
+     * Only the inner category enters/exits per iteration.
+     */
+    @Benchmark
+    void nestedCategoryOuterWrapping(Blackhole bh) {
+        int sum = 0
+        use(StringCategory) {
+            for (int i = 0; i < ITERATIONS; i++) {
+                use(MathCategory) {
+                    sum += testString.shout().length() + i.doubled()
+                }
+            }
+        }
+        bh.consume(sum)
+    }
+
+    // ===== MULTIPLE SIMULTANEOUS CATEGORIES =====
+
+    /**
+     * Multiple categories applied simultaneously via use(Cat1, Cat2).
+     * Single enter/exit but with more method resolution complexity.
+     */
+    @Benchmark
+    void multipleCategoriesSimultaneous(Blackhole bh) {
+        int sum = 0
+        for (int i = 0; i < ITERATIONS; i++) {
+            use(StringCategory, MathCategory) {
+                sum += testString.shout().length() + i.doubled()
+            }
+        }
+        bh.consume(sum)
+    }
+
+    /**
+     * Three categories simultaneously - heavier resolution load.
+     */
+    @Benchmark
+    void threeCategoriesSimultaneous(Blackhole bh) {
+        int sum = 0
+        for (int i = 0; i < ITERATIONS; i++) {
+            use(StringCategory, MathCategory, CollectionCategory) {
+                sum += testString.shout().length() + i.doubled() + testList.sumAll()
+            }
+        }
+        bh.consume(sum)
+    }
+
+    // ===== CATEGORY WITH OUTSIDE CALLS =====
+
+    /**
+     * Method calls both inside and outside category scope.
+     * The outside calls exercise call sites that were invalidated
+     * when the category scope was entered/exited. This measures
+     * the collateral damage of category usage on non-category code.
+     */
+    @Benchmark
+    void categoryWithOutsideCalls(Blackhole bh) {
+        int sum = 0
+        for (int i = 0; i < ITERATIONS; i++) {
+            // Call outside category scope
+            sum += testString.length()
+
+            // Enter/exit category scope (triggers invalidation)
+            use(StringCategory) {
+                sum += testString.shout().length()
+            }
+
+            // Call outside again - call site was invalidated by use() above
+            sum += testString.length()
+        }
+        bh.consume(sum)
+    }
+
+    /**
+     * Baseline for category-with-outside-calls: same work without
+     * the category block. Shows how much the category enter/exit
+     * overhead costs for the surrounding non-category calls.
+     */
+    @Benchmark
+    void baselineEquivalentWithoutCategory(Blackhole bh) {
+        int sum = 0
+        for (int i = 0; i < ITERATIONS; i++) {
+            sum += testString.length()
+            sum += testString.toUpperCase().length() + 1  // same work as shout()
+            sum += testString.length()
+        }
+        bh.consume(sum)
+    }
+
+    // ===== CATEGORY METHOD RESOLUTION =====
+
+    /**
+     * Category method that shadows an existing method.
+     * Tests the overhead of category method resolution when the
+     * category method name matches a method already on the class.
+     */
+    @Benchmark
+    void categoryShadowingExistingMethod(Blackhole bh) {
+        int sum = 0
+        for (int i = 0; i < ITERATIONS; i++) {
+            use(StringCategory) {
+                // reverse() exists on String AND in StringCategory
+                sum += testString.reverse().length()
+            }
+        }
+        bh.consume(sum)
+    }
+}