--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/jfr/recorder/checkpoint/types/traceid/jfrTraceId.hpp Tue May 15 20:24:34 2018 +0200
@@ -0,0 +1,128 @@
+/*
+ * Copyright (c) 2011, 2018, 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.
+ *
+ * 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.
+ *
+ */
+
+#ifndef SHARE_VM_JFR_CHECKPOINT_TYPES_TRACEID_JFRTRACEID_HPP
+#define SHARE_VM_JFR_CHECKPOINT_TYPES_TRACEID_JFRTRACEID_HPP
+
+#include "jni.h"
+#include "jfr/utilities/jfrTypes.hpp"
+#include "memory/allocation.hpp"
+
+class ClassLoaderData;
+class Klass;
+class Method;
+class ModuleEntry;
+class PackageEntry;
+class Thread;
+
+/*
+ * JfrTraceId is a means of tagging, e.g. marking, specific instances as being actively in-use.
+ * The most common situation is a committed event that has a field that is referring to a specific instance.
+ * Now there exist a relation between an event (field) and an artifact of some kind.
+ * We track this relation during runtime using the JfrTraceId mechanism in order to reify it into the chunk
+ * where the event is finally written.
+ *
+ * It is the event commit mechanism that tags instances as in-use. The tag routines return the untagged traceid
+ * as a mapping key, and the commit mechanism writes the key into the event field.
+ * Consequently, the mechanism is opaque and not something a user needs to know about.
+ * Indeed, the API promotes using well-known JVM concepts directly in events, such as having a Klass* as an event field.
+ *
+ * Tagging allows for many-to-one mappings of constants, lazy evaluation / collection of tags during chunk rotation
+ * and concurrency (by using an epoch relative tagging scheme).
+ *
+ * JfrTraceId(s) have been added to support tagging instances of classes such as:
+ *
+ * Klass (includes Method)
+ * ClassLoaderData
+ * ModuleEntry
+ * PackageEntry
+ *
+ * These classes have been extended to include a _traceid field (64-bits).
+ *
+ * Each instance is uniquely identified by a type-relative monotonic counter that is unique over the VM lifecycle.
+ * "Tagging an instance" essentially means to set contextually determined (by epoch) marker bits in the _traceid field.
+ * The constants associated with a tagged instance is a set of which is determined by a constant type definition,
+ * and these constants are then serialized in an upcoming checkpoint event for the relevant chunk.
+ *
+ * Note that a "tagging" is relative to a chunk. Having serialized the tagged instance, the tag bits are reset (for that epoch).
+ * As mentioned previously, the returned traceid is always the untagged value.
+ *
+ * We also use the _traceid field in Klass to quickly identify (bit check) if a newly loaded klass is of type jdk.jfr.Event.
+ * (see jfr/instrumentation/jfrEventClassTransformer.cpp)
+ *
+ *
+ * _traceid bit layout and description planned to go here
+ *
+ *
+ */
+
+class JfrTraceId : public AllStatic {
+ public:
+ static void assign(const Klass* klass);
+ static void assign(const ModuleEntry* module);
+ static void assign(const PackageEntry* package);
+ static void assign(const ClassLoaderData* cld);
+ static traceid assign_thread_id();
+
+ static traceid get(const Klass* klass);
+ static traceid get(jclass jc);
+ static traceid get(const Thread* thread);
+
+ // tag construct as used, returns pre-tagged traceid
+ static traceid use(const Klass* klass, bool leakp = false);
+ static traceid use(jclass jc, bool leakp = false);
+ static traceid use(const Method* method, bool leakp = false);
+ static traceid use(const ModuleEntry* module, bool leakp = false);
+ static traceid use(const PackageEntry* package, bool leakp = false);
+ static traceid use(const ClassLoaderData* cld, bool leakp = false);
+
+ static void remove(const Klass* klass);
+ static void restore(const Klass* klass);
+
+ // set of event classes made visible to java
+ static bool in_visible_set(const Klass* k);
+ static bool in_visible_set(const jclass jc);
+
+ // jdk.jfr.Event
+ static bool is_jdk_jfr_event(const Klass* k);
+ static bool is_jdk_jfr_event(const jclass jc);
+ static void tag_as_jdk_jfr_event(const Klass* k);
+
+ // jdk.jfr.Event subklasses
+ static bool is_jdk_jfr_event_sub(const Klass* k);
+ static bool is_jdk_jfr_event_sub(const jclass jc);
+ static void tag_as_jdk_jfr_event_sub(const Klass* k);
+ static void tag_as_jdk_jfr_event_sub(const jclass jc);
+
+ static bool in_jdk_jfr_event_hierarchy(const Klass* k);
+ static bool in_jdk_jfr_event_hierarchy(const jclass jc);
+
+ // klasses that host an event
+ static bool is_event_host(const Klass* k);
+ static bool is_event_host(const jclass jc);
+ static void tag_as_event_host(const Klass* k);
+ static void tag_as_event_host(const jclass jc);
+};
+
+#endif // SHARE_VM_JFR_CHECKPOINT_TYPES_TRACEID_JFRTRACEID_HPP