8003216: Add JFR event indicating explicit System.gc() call

Reviewed-by: jbachorik, mgronlun, tschatzl

Author: egahlin

src/hotspot/share/jfr/metadata/metadata.xml

@@ -278,6 +278,10 @@
     <Field type="Tickspan" name="longestPause" label="Longest Pause" description="Longest individual pause during the garbage collection" />
   </Event>
 
+  <Event name="SystemGC" category="Java Virtual Machine, GC, Collector" label="System GC" stackTrace="true" startTime="true" thread="true">
+    <Field type="boolean" name="invokedConcurrent" label="Invoked Concurrent" />
+  </Event>
+
   <Event name="ParallelOldGarbageCollection" category="Java Virtual Machine, GC, Collector" label="Parallel Old Garbage Collection"
     description="Extra information specific to Parallel Old Garbage Collections">
     <Field type="uint" name="gcId" label="GC Identifier" relation="GcId" />

src/hotspot/share/prims/jvm.cpp

@@ -443,7 +443,10 @@ JVM_END
 
 JVM_ENTRY_NO_ENV(void, JVM_GC(void))
   if (!DisableExplicitGC) {
+    EventSystemGC event;
+    event.set_invokedConcurrent(ExplicitGCInvokesConcurrent);
     Universe::heap()->collect(GCCause::_java_lang_system_gc);
+    event.commit();
   }
 JVM_END
 

src/jdk.jfr/share/conf/jfr/default.jfc

@@ -346,6 +346,12 @@
       <setting name="threshold">0 ms</setting>
     </event>
 
+    <event name="jdk.SystemGC">
+      <setting name="enabled">true</setting>
+      <setting name="threshold">0 ms</setting>
+      <setting name="stackTrace">true</setting>
+    </event>
+
     <event name="jdk.ParallelOldGarbageCollection">
       <setting name="enabled" control="gc-enabled-normal">true</setting>
       <setting name="threshold">0 ms</setting>

src/jdk.jfr/share/conf/jfr/profile.jfc

@@ -346,6 +346,12 @@
       <setting name="threshold">0 ms</setting>
     </event>
 
+    <event name="jdk.SystemGC">
+      <setting name="enabled">true</setting>
+      <setting name="threshold">0 ms</setting>
+      <setting name="stackTrace">true</setting> 
+    </event>
+
     <event name="jdk.ParallelOldGarbageCollection">
       <setting name="enabled" control="gc-enabled-normal">true</setting>
       <setting name="threshold">0 ms</setting>

test/jdk/jdk/jfr/event/gc/collection/TestSystemGc.java

@@ -0,0 +1,79 @@
+/*
+ * Copyright (c) 2020, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+package jdk.jfr.event.gc.collection;
+
+import java.lang.management.ManagementFactory;
+import java.util.List;
+
+import jdk.jfr.Recording;
+import jdk.jfr.consumer.RecordedEvent;
+import jdk.test.lib.Asserts;
+import jdk.test.lib.jfr.EventNames;
+import jdk.test.lib.jfr.Events;
+
+/**
+ * @test
+ * @key jfr
+ * @requires vm.hasJFR
+ * @library /test/lib /test/jdk
+ * @run main/othervm -XX:+ExplicitGCInvokesConcurrent jdk.jfr.event.gc.collection.TestSystemGC true
+ * @run main/othervm -XX:-ExplicitGCInvokesConcurrent jdk.jfr.event.gc.collection.TestSystemGC false
+ */
+public class TestSystemGC {
+    public static void main(String[] args) throws Exception {
+        boolean concurrent = Boolean.valueOf(args[0]);
+        try (Recording recording = new Recording()) {
+            recording.enable(EventNames.SystemGC);
+            recording.start();
+
+            // Trigger 3 System GC
+            System.gc();
+            ManagementFactory.getMemoryMXBean().gc();
+            Runtime.getRuntime().gc();
+
+            recording.stop();
+            List<RecordedEvent> events = Events.fromRecording(recording);
+            System.out.println(events);
+
+            Asserts.assertEquals(3, events.size(), "Expected 3 SystemGC events");
+
+            RecordedEvent event1 = events.get(0);
+            Events.assertFrame(event1, System.class, "gc");
+            Events.assertEventThread(event1, Thread.currentThread());
+            Events.assertField(event1, "invokedConcurrent").isEqual(concurrent);
+
+            RecordedEvent event2 = events.get(1);
+            Events.assertFrame(event2, Runtime.class, "gc");
+            Events.assertEventThread(event2, Thread.currentThread());
+            Events.assertField(event1, "invokedConcurrent").isEqual(concurrent);
+
+            RecordedEvent event3 = events.get(2);
+            // MemoryMXBean.class is an interface so can't assertFrame on it
+            Events.assertEventThread(event3, Thread.currentThread());
+            Events.assertField(event1, "invokedConcurrent").isEqual(concurrent);
+        }
+     }
+}

test/lib/jdk/test/lib/jfr/EventNames.java

@@ -150,6 +150,7 @@ public class EventNames {
     public final static String ZUncommit = PREFIX + "ZUncommit";
     public final static String ZUnmap = PREFIX + "ZUnmap";
     public final static String GCLocker = PREFIX + "GCLocker";
+    public static final String SystemGC = PREFIX + "SystemGC";
 
     // Compiler
     public final static String Compilation = PREFIX + "Compilation";