--- a/hotspot/src/share/vm/memory/metaspace.cpp	Mon Mar 17 17:31:46 2014 +0100
+++ b/hotspot/src/share/vm/memory/metaspace.cpp	Mon Mar 17 20:59:19 2014 +0100
@@ -32,7 +32,9 @@
 #include "memory/gcLocker.hpp"
 #include "memory/metachunk.hpp"
 #include "memory/metaspace.hpp"
+#include "memory/metaspaceGCThresholdUpdater.hpp"
 #include "memory/metaspaceShared.hpp"
+#include "memory/metaspaceTracer.hpp"
 #include "memory/resourceArea.hpp"
 #include "memory/universe.hpp"
 #include "runtime/atomic.inline.hpp"
@@ -57,6 +59,7 @@
 MetaWord* last_allocated = 0;
 
 size_t Metaspace::_compressed_class_space_size;
+const MetaspaceTracer* Metaspace::_tracer = NULL;
 
 // Used in declarations in SpaceManager and ChunkManager
 enum ChunkIndex {
@@ -1436,19 +1439,21 @@
     expand_bytes = align_size_up(expand_bytes, Metaspace::commit_alignment());
     // Don't expand unless it's significant
     if (expand_bytes >= MinMetaspaceExpansion) {
-      MetaspaceGC::inc_capacity_until_GC(expand_bytes);
-    }
-    if (PrintGCDetails && Verbose) {
-      size_t new_capacity_until_GC = capacity_until_GC;
-      gclog_or_tty->print_cr("    expanding:"
-                    "  minimum_desired_capacity: %6.1fKB"
-                    "  expand_bytes: %6.1fKB"
-                    "  MinMetaspaceExpansion: %6.1fKB"
-                    "  new metaspace HWM:  %6.1fKB",
-                    minimum_desired_capacity / (double) K,
-                    expand_bytes / (double) K,
-                    MinMetaspaceExpansion / (double) K,
-                    new_capacity_until_GC / (double) K);
+      size_t new_capacity_until_GC = MetaspaceGC::inc_capacity_until_GC(expand_bytes);
+      Metaspace::tracer()->report_gc_threshold(capacity_until_GC,
+                                               new_capacity_until_GC,
+                                               MetaspaceGCThresholdUpdater::ComputeNewSize);
+      if (PrintGCDetails && Verbose) {
+        gclog_or_tty->print_cr("    expanding:"
+                      "  minimum_desired_capacity: %6.1fKB"
+                      "  expand_bytes: %6.1fKB"
+                      "  MinMetaspaceExpansion: %6.1fKB"
+                      "  new metaspace HWM:  %6.1fKB",
+                      minimum_desired_capacity / (double) K,
+                      expand_bytes / (double) K,
+                      MinMetaspaceExpansion / (double) K,
+                      new_capacity_until_GC / (double) K);
+      }
     }
     return;
   }
@@ -1528,7 +1533,10 @@
   // Don't shrink unless it's significant
   if (shrink_bytes >= MinMetaspaceExpansion &&
       ((capacity_until_GC - shrink_bytes) >= MetaspaceSize)) {
-    MetaspaceGC::dec_capacity_until_GC(shrink_bytes);
+    size_t new_capacity_until_GC = MetaspaceGC::dec_capacity_until_GC(shrink_bytes);
+    Metaspace::tracer()->report_gc_threshold(capacity_until_GC,
+                                             new_capacity_until_GC,
+                                             MetaspaceGCThresholdUpdater::ComputeNewSize);
   }
 }
 
@@ -3132,6 +3140,7 @@
   }
 
   MetaspaceGC::initialize();
+  _tracer = new MetaspaceTracer();
 }
 
 Metachunk* Metaspace::get_initialization_chunk(MetadataType mdtype,
@@ -3220,8 +3229,12 @@
   assert(delta_bytes > 0, "Must be");
 
   size_t after_inc = MetaspaceGC::inc_capacity_until_GC(delta_bytes);
+
+  // capacity_until_GC might be updated concurrently, must calculate previous value.
   size_t before_inc = after_inc - delta_bytes;
 
+  tracer()->report_gc_threshold(before_inc, after_inc,
+                                MetaspaceGCThresholdUpdater::ExpandAndAllocate);
   if (PrintGCDetails && Verbose) {
     gclog_or_tty->print_cr("Increase capacity to GC from " SIZE_FORMAT
         " to " SIZE_FORMAT, before_inc, after_inc);

--- a/hotspot/src/share/vm/memory/metaspace.hpp	Mon Mar 17 17:31:46 2014 +0100
+++ b/hotspot/src/share/vm/memory/metaspace.hpp	Mon Mar 17 20:59:19 2014 +0100
@@ -60,6 +60,7 @@
 class ClassLoaderData;
 class Metablock;
 class Metachunk;
+class MetaspaceTracer;
 class MetaWord;
 class Mutex;
 class outputStream;
@@ -149,6 +150,8 @@
   static ChunkManager* _chunk_manager_metadata;
   static ChunkManager* _chunk_manager_class;
 
+  static const MetaspaceTracer* _tracer;
+
  public:
   static VirtualSpaceList* space_list()       { return _space_list; }
   static VirtualSpaceList* class_space_list() { return _class_space_list; }
@@ -164,6 +167,8 @@
     return mdtype == ClassType ? chunk_manager_class() : chunk_manager_metadata();
   }
 
+  static const MetaspaceTracer* tracer() { return _tracer; }
+
  private:
   // This is used by DumpSharedSpaces only, where only _vsm is used. So we will
   // maintain a single list for now.

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/memory/metaspaceGCThresholdUpdater.hpp	Mon Mar 17 20:59:19 2014 +0100
@@ -0,0 +1,52 @@
+/*
+ * Copyright (c) 2014, 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_MEMORY_METASPACE_GC_THRESHOLD_UPDATER_HPP
+#define SHARE_VM_MEMORY_METASPACE_GC_THRESHOLD_UPDATER_HPP
+
+#include "memory/allocation.hpp"
+#include "utilities/debug.hpp"
+
+class MetaspaceGCThresholdUpdater : public AllStatic {
+ public:
+  enum Type {
+    ComputeNewSize,
+    ExpandAndAllocate,
+    Last
+  };
+
+  static const char* to_string(MetaspaceGCThresholdUpdater::Type updater) {
+    switch (updater) {
+      case ComputeNewSize:
+        return "compute_new_size";
+      case ExpandAndAllocate:
+        return "expand_and_allocate";
+      default:
+        assert(false, err_msg("Got bad updater: %d", (int) updater));
+        return NULL;
+    };
+  }
+};
+
+#endif // SHARE_VM_MEMORY_METASPACE_GC_THRESHOLD_UPDATER_HPP

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/memory/metaspaceTracer.cpp	Mon Mar 17 20:59:19 2014 +0100
@@ -0,0 +1,40 @@
+/*
+ * Copyright (c) 2014, 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 "memory/metaspaceTracer.hpp"
+#include "trace/tracing.hpp"
+#include "trace/traceBackend.hpp"
+
+void MetaspaceTracer::report_gc_threshold(size_t old_val,
+                                          size_t new_val,
+                                          MetaspaceGCThresholdUpdater::Type updater) const {
+  EventMetaspaceGCThreshold event;
+  if (event.should_commit()) {
+    event.set_oldValue(old_val);
+    event.set_newValue(new_val);
+    event.set_updater((u1)updater);
+    event.commit();
+  }
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/memory/metaspaceTracer.hpp	Mon Mar 17 20:59:19 2014 +0100
@@ -0,0 +1,38 @@
+/*
+ * Copyright (c) 2014, 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_MEMORY_METASPACE_TRACER_HPP
+#define SHARE_VM_MEMORY_METASPACE_TRACER_HPP
+
+#include "memory/allocation.hpp"
+#include "memory/metaspaceGCThresholdUpdater.hpp"
+
+class MetaspaceTracer : public CHeapObj<mtTracing> {
+ public:
+  void report_gc_threshold(size_t old_val,
+                           size_t new_val,
+                           MetaspaceGCThresholdUpdater::Type updater) const;
+};
+
+#endif // SHARE_VM_MEMORY_METASPACE_TRACER_HPP

--- a/hotspot/src/share/vm/trace/trace.xml	Mon Mar 17 17:31:46 2014 +0100
+++ b/hotspot/src/share/vm/trace/trace.xml	Mon Mar 17 20:59:19 2014 +0100
@@ -199,6 +199,12 @@
       <structvalue type="MetaspaceSizes" field="classSpace" label="Class"/>
     </event>
 
+    <event id="MetaspaceGCThreshold" path="vm/gc/metaspace/gc_threshold" label="Metaspace GC Threshold" is_instant="true">
+      <value type="BYTES64" field="oldValue" label="Old Value" />
+      <value type="BYTES64" field="newValue" label="New Value" />
+      <value type="GCTHRESHOLDUPDATER" field="updater" label="Updater" />
+    </event>
+
     <event id="PSHeapSummary" path="vm/gc/heap/ps_summary" label="Parallel Scavenge Heap Summary" is_instant="true">
       <value type="UINT" field="gcId" label="GC ID" relation="GC_ID"/>
       <value type="GCWHEN" field="when" label="When" />

--- a/hotspot/src/share/vm/trace/tracetypes.xml	Mon Mar 17 17:31:46 2014 +0100
+++ b/hotspot/src/share/vm/trace/tracetypes.xml	Mon Mar 17 20:59:19 2014 +0100
@@ -130,6 +130,11 @@
       <value type="UTF8" field="type" label="type" />
     </content_type>
 
+    <content_type id="GCThresholdUpdater" hr_name="GC Treshold Updater"
+                  type="U1" jvm_type="GCTHRESHOLDUPDATER">
+      <value type="UTF8" field="updater" label="updater" />
+    </content_type>
+
     <content_type id="ReferenceType" hr_name="Reference Type"
                   type="U1" jvm_type="REFERENCETYPE">
       <value type="UTF8" field="type" label="type" />
@@ -324,6 +329,10 @@
     <primary_type symbol="G1YCTYPE" datatype="U1" contenttype="G1YCTYPE"
                   type="u1" sizeop="sizeof(u1)" />
 
+    <!-- GCTHRESHOLDUPDATER -->
+    <primary_type symbol="GCTHRESHOLDUPDATER" datatype="U1" contenttype="GCTHRESHOLDUPDATER"
+                  type="u1" sizeop="sizeof(u1)" />
+
     <!-- REFERENCETYPE -->
     <primary_type symbol="REFERENCETYPE" datatype="U1"
                   contenttype="REFERENCETYPE" type="u1" sizeop="sizeof(u1)" />