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24 
25 #ifndef SHARE_VM_JFR_CHECKPOINT_TYPES_TRACEID_JFRTRACEID_HPP
26 #define SHARE_VM_JFR_CHECKPOINT_TYPES_TRACEID_JFRTRACEID_HPP
27 
28 #include "jni.h"
29 #include "jfr/utilities/jfrTypes.hpp"
30 #include "memory/allocation.hpp"
31 
32 class ClassLoaderData;
33 class Klass;
34 class Method;
35 class ModuleEntry;
36 class PackageEntry;
37 class Thread;
38 
39 /*
40  * JfrTraceId is a means of tagging, e.g. marking, specific instances as being actively in-use.
41  * The most common situation is a committed event that has a field that is referring to a specific instance.
42  * Now there exist a relation between an event (field) and an artifact of some kind.
43  * We track this relation during runtime using the JfrTraceId mechanism in order to reify it into the chunk
44  * where the event is finally written.
45  *
46  * It is the event commit mechanism that tags instances as in-use. The tag routines return the untagged traceid
47  * as a mapping key, and the commit mechanism writes the key into the event field.
48  * Consequently, the mechanism is opaque and not something a user needs to know about.
49  * Indeed, the API promotes using well-known JVM concepts directly in events, such as having a Klass* as an event field.
50  *
51  * Tagging allows for many-to-one mappings of constants, lazy evaluation / collection of tags during chunk rotation
52  * and concurrency (by using an epoch relative tagging scheme).
53  *
54  * JfrTraceId(s) have been added to support tagging instances of classes such as:
55  *
56  *   Klass (includes Method)
57  *   ClassLoaderData
58  *   ModuleEntry
59  *   PackageEntry
60  *
61  * These classes have been extended to include a _traceid field (64-bits).
62  *
63  * Each instance is uniquely identified by a type-relative monotonic counter that is unique over the VM lifecycle.
64  * "Tagging an instance" essentially means to set contextually determined (by epoch) marker bits in the _traceid field.
65  * The constants associated with a tagged instance is a set of which is determined by a constant type definition,
66  * and these constants are then serialized in an upcoming checkpoint event for the relevant chunk.
67  *
68  * Note that a "tagging" is relative to a chunk. Having serialized the tagged instance, the tag bits are reset (for that epoch).
69  * As mentioned previously, the returned traceid is always the untagged value.
70  *
71  * We also use the _traceid field in Klass to quickly identify (bit check) if a newly loaded klass is of type jdk.jfr.Event.
72  * (see jfr/instrumentation/jfrEventClassTransformer.cpp)
73  *
74  *
75  * _traceid bit layout and description planned to go here
76  *
77  *
78  */
79 
80 class JfrTraceId : public AllStatic {
81  public:
82   static void assign(const Klass* klass);
83   static void assign(const ModuleEntry* module);
84   static void assign(const PackageEntry* package);
85   static void assign(const ClassLoaderData* cld);
86   static traceid assign_primitive_klass_id();
87   static traceid assign_thread_id();
88 
89   static traceid get(const Klass* klass);
90   static traceid get(jclass jc);
91   static traceid get(const Thread* thread);
92 
93   // tag construct as used, returns pre-tagged traceid
94   static traceid use(const Klass* klass);
95   static traceid use(jclass jc, bool raw = false);
96   static traceid use(const Method* method);
97   static traceid use(const Klass* klass, const Method* method);
98   static traceid use(const ModuleEntry* module);
99   static traceid use(const PackageEntry* package);
100   static traceid use(const ClassLoaderData* cld);
101 
102   // leak profiler
103   static void set_leakp(const Method* method);
104 
105   static void remove(const Klass* klass);
106   static void restore(const Klass* klass);
107 
108   // set of event classes made visible to java
109   static bool in_visible_set(const Klass* k);
110   static bool in_visible_set(const jclass jc);
111 
112   // jdk.jfr.Event
113   static bool is_jdk_jfr_event(const Klass* k);
114   static bool is_jdk_jfr_event(const jclass jc);
115   static void tag_as_jdk_jfr_event(const Klass* k);
116 
117   // jdk.jfr.Event subklasses
118   static bool is_jdk_jfr_event_sub(const Klass* k);
119   static bool is_jdk_jfr_event_sub(const jclass jc);
120   static void tag_as_jdk_jfr_event_sub(const Klass* k);
121   static void tag_as_jdk_jfr_event_sub(const jclass jc);
122 
123   static bool in_jdk_jfr_event_hierarchy(const Klass* k);
124   static bool in_jdk_jfr_event_hierarchy(const jclass jc);
125 
126   // klasses that host an event
127   static bool is_event_host(const Klass* k);
128   static bool is_event_host(const jclass jc);
129   static void tag_as_event_host(const Klass* k);
130   static void tag_as_event_host(const jclass jc);
131 };
132 
133 #endif // SHARE_VM_JFR_CHECKPOINT_TYPES_TRACEID_JFRTRACEID_HPP
134