--- /dev/null	2017-11-09 09:38:01.297999907 +0100
+++ new/src/hotspot/share/jfr/recorder/access/jfrFlush.cpp	2018-04-09 14:54:13.363211774 +0200
@@ -0,0 +1,86 @@
+/*
+ * Copyright (c) 2016, 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 "jfr/recorder/access/jfrFlush.hpp"
+#include "jfr/recorder/access/jfrThreadData.hpp"
+#include "jfr/recorder/jfrEventSetting.inline.hpp"
+#include "jfr/recorder/storage/jfrStorage.hpp"
+#include "jfr/recorder/stacktrace/jfrStackTraceRepository.hpp"
+#include "runtime/thread.inline.hpp"
+#include "utilities/debug.hpp"
+
+
+JfrFlush::JfrFlush(JfrStorage::Buffer* old, size_t used, size_t requested, Thread* t) :
+  _result(JfrStorage::flush(old, used, requested, true, t)) {
+}
+
+template <typename T>
+class LessThanHalfBufferSize : AllStatic {
+public:
+  static bool evaluate(T* t) {
+    assert(t != NULL, "invariant");
+    return t->free_size() < t->size() / 2;
+  }
+};
+
+template <typename T>
+class LessThanSize : AllStatic {
+ public:
+  static bool evaluate(T* t, size_t size) {
+    assert(t != NULL, "invariant");
+    return t->free_size() < size;
+  }
+};
+
+bool jfr_is_event_enabled(TraceEventId id) {
+  return JfrEventSetting::is_enabled(id);
+}
+
+bool jfr_has_stacktrace_enabled(TraceEventId id) {
+  return JfrEventSetting::has_stacktrace(id);
+}
+
+void jfr_conditional_flush(TraceEventId id, size_t size, Thread* t) {
+  assert(jfr_is_event_enabled(id), "invariant");
+  if (t->trace_data()->has_native_buffer()) {
+    JfrStorage::Buffer* const buffer = t->trace_data()->native_buffer();
+    if (LessThanSize<JfrStorage::Buffer>::evaluate(buffer, size)) {
+      JfrFlush f(buffer, 0, 0, t);
+    }
+  }
+}
+
+bool jfr_save_stacktrace(Thread* t) {
+  JfrThreadData* const trace_data = t->trace_data();
+  if (trace_data->has_cached_stack_trace()) {
+    return false; // no ownership
+  }
+  trace_data->set_cached_stack_trace_id(JfrStackTraceRepository::record(t));
+  return true;
+}
+
+void jfr_clear_stacktrace(Thread* t) {
+  t->trace_data()->clear_cached_stack_trace();
+}