--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/jfr/periodic/jfrThreadCPULoadEvent.cpp	Tue May 15 20:24:34 2018 +0200
@@ -0,0 +1,145 @@
+/*
+ * Copyright (c) 2017, 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.
+ *
+ */
+
+#include "precompiled.hpp"
+#include "logging/log.hpp"
+#include "jfr/jfrEvents.hpp"
+#include "jfr/periodic/jfrThreadCPULoadEvent.hpp"
+#include "jfr/support/jfrThreadId.hpp"
+#include "jfr/support/jfrThreadLocal.hpp"
+#include "jfr/utilities/jfrTime.hpp"
+#include "utilities/globalDefinitions.hpp"
+#include "runtime/os.hpp"
+#include "runtime/thread.inline.hpp"
+#include "runtime/threadSMR.inline.hpp"
+
+jlong JfrThreadCPULoadEvent::get_wallclock_time() {
+  return os::javaTimeNanos();
+}
+
+int JfrThreadCPULoadEvent::_last_active_processor_count = 0;
+
+int JfrThreadCPULoadEvent::get_processor_count() {
+  int cur_processor_count = os::active_processor_count();
+  int last_processor_count = _last_active_processor_count;
+  _last_active_processor_count = cur_processor_count;
+
+  // If the number of processors decreases, we don't know at what point during
+  // the sample interval this happened, so use the largest number to try
+  // to avoid percentages above 100%
+  return MAX2(cur_processor_count, last_processor_count);
+}
+
+// Returns false if the thread has not been scheduled since the last call to updateEvent
+// (i.e. the delta for both system and user time is 0 milliseconds)
+bool JfrThreadCPULoadEvent::update_event(EventThreadCPULoad& event, JavaThread* thread, jlong cur_wallclock_time, int processor_count) {
+  JfrThreadLocal* const tl = thread->jfr_thread_local();
+
+  jlong cur_cpu_time = os::thread_cpu_time(thread, true);
+  jlong prev_cpu_time = tl->get_cpu_time();
+
+  jlong prev_wallclock_time = tl->get_wallclock_time();
+  tl->set_wallclock_time(cur_wallclock_time);
+
+  // Threshold of 1 ms
+  if (cur_cpu_time - prev_cpu_time < 1 * NANOSECS_PER_MILLISEC) {
+    return false;
+  }
+
+  jlong cur_user_time = os::thread_cpu_time(thread, false);
+  jlong prev_user_time = tl->get_user_time();
+
+  jlong cur_system_time = cur_cpu_time - cur_user_time;
+  jlong prev_system_time = prev_cpu_time - prev_user_time;
+
+  // The user and total cpu usage clocks can have different resolutions, which can
+  // make us see decreasing system time. Ensure time doesn't go backwards.
+  if (prev_system_time > cur_system_time) {
+    cur_cpu_time += prev_system_time - cur_system_time;
+    cur_system_time = prev_system_time;
+  }
+
+  jlong user_time = cur_user_time - prev_user_time;
+  jlong system_time = cur_system_time - prev_system_time;
+  jlong wallclock_time = cur_wallclock_time - prev_wallclock_time;
+  jlong total_available_time = wallclock_time * processor_count;
+
+  // Avoid reporting percentages above the theoretical max
+  if (user_time + system_time > wallclock_time) {
+    jlong excess = user_time + system_time - wallclock_time;
+    if (user_time > excess) {
+      user_time -= excess;
+      cur_user_time -= excess;
+      cur_cpu_time -= excess;
+    } else {
+      cur_cpu_time -= excess;
+      excess -= user_time;
+      user_time = 0;
+      cur_user_time = 0;
+      system_time -= excess;
+    }
+  }
+  event.set_user(total_available_time > 0 ? (double)user_time / total_available_time : 0);
+  event.set_system(total_available_time > 0 ? (double)system_time / total_available_time : 0);
+  tl->set_user_time(cur_user_time);
+  tl->set_cpu_time(cur_cpu_time);
+  return true;
+}
+
+void JfrThreadCPULoadEvent::send_events() {
+  Thread* periodic_thread = Thread::current();
+  JfrThreadLocal* const periodic_thread_tl = periodic_thread->jfr_thread_local();
+  traceid periodic_thread_id = periodic_thread_tl->thread_id();
+  const int processor_count = JfrThreadCPULoadEvent::get_processor_count();
+  JfrTicks event_time = JfrTicks::now();
+  jlong cur_wallclock_time = JfrThreadCPULoadEvent::get_wallclock_time();
+
+  JavaThreadIteratorWithHandle jtiwh;
+  while (JavaThread* jt = jtiwh.next()) {
+    EventThreadCPULoad event(UNTIMED);
+    if (JfrThreadCPULoadEvent::update_event(event, jt, cur_wallclock_time, processor_count)) {
+      event.set_starttime(event_time);
+      if (jt != periodic_thread) {
+        // Commit reads the thread id from this thread's trace data, so put it there temporarily
+        periodic_thread_tl->set_thread_id(JFR_THREAD_ID(jt));
+      } else {
+        periodic_thread_tl->set_thread_id(periodic_thread_id);
+      }
+      event.commit();
+    }
+  }
+  log_trace(jfr)("Measured CPU usage for %d threads in %.3f milliseconds", jtiwh.length(),
+    (double)(JfrTicks::now() - event_time).milliseconds());
+  // Restore this thread's thread id
+  periodic_thread_tl->set_thread_id(periodic_thread_id);
+}
+
+void JfrThreadCPULoadEvent::send_event_for_thread(JavaThread* jt) {
+  EventThreadCPULoad event;
+  if (event.should_commit()) {
+    if (update_event(event, jt, get_wallclock_time(), get_processor_count())) {
+      event.commit();
+    }
+  }
+}