8277397: ZGC: Add JFR event for temporary latency measurements

Reviewed-by: eosterlund, jbachorik, pliden, mgronlun

src/hotspot/share/gc/z/zTracer.cpp

@@ -131,3 +131,16 @@ void ZTracer::send_thread_phase(const char* name, const Ticks& start, const Tick
     e.commit();
   }
 }
+
+void ZTracer::send_thread_debug(const char* name, const Ticks& start, const Ticks& end) {
+  NoSafepointVerifier nsv;
+
+  EventZThreadDebug e(UNTIMED);
+  if (e.should_commit()) {
+    e.set_gcId(GCId::current_or_undefined());
+    e.set_name(name);
+    e.set_starttime(start);
+    e.set_endtime(end);
+    e.commit();
+  }
+}

src/hotspot/share/gc/z/zTracer.hpp

@@ -39,6 +39,7 @@ private:
   void send_stat_counter(const ZStatCounter& counter, uint64_t increment, uint64_t value);
   void send_stat_sampler(const ZStatSampler& sampler, uint64_t value);
   void send_thread_phase(const char* name, const Ticks& start, const Ticks& end);
+  void send_thread_debug(const char* name, const Ticks& start, const Ticks& end);
 
 public:
   static ZTracer* tracer();
@@ -47,16 +48,18 @@ public:
   void report_stat_counter(const ZStatCounter& counter, uint64_t increment, uint64_t value);
   void report_stat_sampler(const ZStatSampler& sampler, uint64_t value);
   void report_thread_phase(const char* name, const Ticks& start, const Ticks& end);
+  void report_thread_debug(const char* name, const Ticks& start, const Ticks& end);
 };
 
-class ZTraceThreadPhase : public StackObj {
+// For temporary latency measurements during development and debugging
+class ZTraceThreadDebug : public StackObj {
 private:
   const Ticks       _start;
   const char* const _name;
 
 public:
-  ZTraceThreadPhase(const char* name);
-  ~ZTraceThreadPhase();
+  ZTraceThreadDebug(const char* name);
+  ~ZTraceThreadDebug();
 };
 
 #endif // SHARE_GC_Z_ZTRACER_HPP

src/hotspot/share/gc/z/zTracer.inline.hpp

@@ -50,12 +50,18 @@ inline void ZTracer::report_thread_phase(const char* name, const Ticks& start, c
   }
 }
 
-inline ZTraceThreadPhase::ZTraceThreadPhase(const char* name) :
+inline void ZTracer::report_thread_debug(const char* name, const Ticks& start, const Ticks& end) {
+  if (EventZThreadDebug::is_enabled()) {
+    send_thread_debug(name, start, end);
+  }
+}
+
+inline ZTraceThreadDebug::ZTraceThreadDebug(const char* name) :
     _start(Ticks::now()),
     _name(name) {}
 
-inline ZTraceThreadPhase::~ZTraceThreadPhase() {
-  ZTracer::tracer()->report_thread_phase(_name, _start, Ticks::now());
+inline ZTraceThreadDebug::~ZTraceThreadDebug() {
+  ZTracer::tracer()->report_thread_debug(_name, _start, Ticks::now());
 }
 
 #endif // SHARE_GC_Z_ZTRACER_INLINE_HPP

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

@@ -1034,6 +1034,11 @@
     <Field type="string" name="name" label="Name" />
   </Event>
 
+  <Event name="ZThreadDebug" category="Java Virtual Machine, GC, Detailed" label="ZGC Thread Event" description="Temporary latency measurements used during development and debugging of ZGC" thread="true" experimental="true">
+    <Field type="uint" name="gcId" label="GC Identifier" relation="GcId"/>
+    <Field type="string" name="name" label="Name" />
+  </Event>
+
   <Event name="ZUncommit" category="Java Virtual Machine, GC, Detailed" label="ZGC Uncommit" description="Uncommitting of memory" thread="true">
     <Field type="ulong" contentType="bytes" name="uncommitted" label="Uncommitted" />
   </Event>

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

@@ -775,6 +775,11 @@
       <setting name="threshold">0 ms</setting>
     </event>
 
+    <event name="jdk.ZThreadDebug">
+      <setting name="enabled">true</setting>
+      <setting name="threshold">0 ms</setting>
+    </event>
+
     <event name="jdk.ZUncommit">
       <setting name="enabled">true</setting>
       <setting name="threshold">0 ms</setting>

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

@@ -775,6 +775,11 @@
       <setting name="threshold">0 ms</setting>
     </event>
 
+    <event name="jdk.ZThreadDebug">
+      <setting name="enabled">true</setting>
+      <setting name="threshold">0 ms</setting>
+    </event>
+
     <event name="jdk.ZUncommit">
       <setting name="enabled">true</setting>
       <setting name="threshold">0 ms</setting>