--- a/hotspot/src/share/vm/gc/shared/allocTracer.cpp	Fri Jan 01 17:08:38 2016 +0000
+++ b/hotspot/src/share/vm/gc/shared/allocTracer.cpp	Mon Jan 04 11:27:02 2016 +0100
@@ -46,3 +46,12 @@
     event.commit();
   }
 }
+
+void AllocTracer::send_allocation_requiring_gc_event(size_t size, uint gcId) {
+  EventAllocationRequiringGC event;
+  if (event.should_commit()) {
+    event.set_gcId(gcId);
+    event.set_size(size);
+    event.commit();
+  }
+}

--- a/hotspot/src/share/vm/gc/shared/allocTracer.hpp	Fri Jan 01 17:08:38 2016 +0000
+++ b/hotspot/src/share/vm/gc/shared/allocTracer.hpp	Mon Jan 04 11:27:02 2016 +0100
@@ -32,6 +32,7 @@
   public:
     static void send_allocation_outside_tlab_event(KlassHandle klass, size_t alloc_size);
     static void send_allocation_in_new_tlab_event(KlassHandle klass, size_t tlab_size, size_t alloc_size);
+    static void send_allocation_requiring_gc_event(size_t size, uint gcId);
 };
 
 #endif // SHARE_VM_GC_SHARED_ALLOCTRACER_HPP

--- a/hotspot/src/share/vm/gc/shared/gcId.cpp	Fri Jan 01 17:08:38 2016 +0000
+++ b/hotspot/src/share/vm/gc/shared/gcId.cpp	Mon Jan 04 11:27:02 2016 +0100
@@ -39,6 +39,10 @@
   return _next_id++;
 }
 
+const uint GCId::peek() {
+  return _next_id;
+}
+
 const uint GCId::current() {
   assert(currentNamedthread()->gc_id() != undefined(), "Using undefined GC id.");
   return current_raw();

--- a/hotspot/src/share/vm/gc/shared/gcId.hpp	Fri Jan 01 17:08:38 2016 +0000
+++ b/hotspot/src/share/vm/gc/shared/gcId.hpp	Mon Jan 04 11:27:02 2016 +0100
@@ -39,6 +39,8 @@
   static const uint current();
   // Same as current() but can return undefined() if no GC id is currently active
   static const uint current_raw();
+  // Returns the next expected GCId.
+  static const uint peek();
   static const uint undefined() { return UNDEFINED; }
   static size_t print_prefix(char* buf, size_t len);
 };

--- a/hotspot/src/share/vm/gc/shared/vmGCOperations.cpp	Fri Jan 01 17:08:38 2016 +0000
+++ b/hotspot/src/share/vm/gc/shared/vmGCOperations.cpp	Mon Jan 04 11:27:02 2016 +0100
@@ -25,6 +25,8 @@
 #include "precompiled.hpp"
 #include "classfile/classLoader.hpp"
 #include "classfile/javaClasses.hpp"
+#include "gc/shared/allocTracer.hpp"
+#include "gc/shared/gcId.hpp"
 #include "gc/shared/gcLocker.inline.hpp"
 #include "gc/shared/genCollectedHeap.hpp"
 #include "gc/shared/vmGCOperations.hpp"
@@ -188,6 +190,18 @@
   gch->do_full_collection(gch->must_clear_all_soft_refs(), _max_generation);
 }
 
+VM_CollectForMetadataAllocation::VM_CollectForMetadataAllocation(ClassLoaderData* loader_data,
+                                                                 size_t size,
+                                                                 Metaspace::MetadataType mdtype,
+                                                                 uint gc_count_before,
+                                                                 uint full_gc_count_before,
+                                                                 GCCause::Cause gc_cause)
+    : VM_GC_Operation(gc_count_before, gc_cause, full_gc_count_before, true),
+      _loader_data(loader_data), _size(size), _mdtype(mdtype), _result(NULL) {
+  assert(_size != 0, "An allocation should always be requested with this operation.");
+  AllocTracer::send_allocation_requiring_gc_event(_size * HeapWordSize, GCId::peek());
+}
+
 // Returns true iff concurrent GCs unloads metadata.
 bool VM_CollectForMetadataAllocation::initiate_concurrent_GC() {
 #if INCLUDE_ALL_GCS
@@ -279,3 +293,11 @@
     set_gc_locked();
   }
 }
+
+VM_CollectForAllocation::VM_CollectForAllocation(size_t word_size, uint gc_count_before, GCCause::Cause cause)
+    : VM_GC_Operation(gc_count_before, cause), _result(NULL), _word_size(word_size) {
+  // Only report if operation was really caused by an allocation.
+  if (_word_size != 0) {
+    AllocTracer::send_allocation_requiring_gc_event(_word_size * HeapWordSize, GCId::peek());
+  }
+}

--- a/hotspot/src/share/vm/gc/shared/vmGCOperations.hpp	Fri Jan 01 17:08:38 2016 +0000
+++ b/hotspot/src/share/vm/gc/shared/vmGCOperations.hpp	Mon Jan 04 11:27:02 2016 +0100
@@ -166,8 +166,7 @@
   HeapWord* _result;    // Allocation result (NULL if allocation failed)
 
  public:
-  VM_CollectForAllocation(size_t word_size, uint gc_count_before, GCCause::Cause cause)
-    : VM_GC_Operation(gc_count_before, cause), _result(NULL), _word_size(word_size) {}
+  VM_CollectForAllocation(size_t word_size, uint gc_count_before, GCCause::Cause cause);
 
   HeapWord* result() const {
     return _result;
@@ -220,10 +219,7 @@
                                   Metaspace::MetadataType mdtype,
                                   uint gc_count_before,
                                   uint full_gc_count_before,
-                                  GCCause::Cause gc_cause)
-    : VM_GC_Operation(gc_count_before, gc_cause, full_gc_count_before, true),
-      _loader_data(loader_data), _size(size), _mdtype(mdtype), _result(NULL) {
-  }
+                                  GCCause::Cause gc_cause);
 
   virtual VMOp_Type type() const { return VMOp_CollectForMetadataAllocation; }
   virtual void doit();

--- a/hotspot/src/share/vm/trace/trace.xml	Fri Jan 01 17:08:38 2016 +0000
+++ b/hotspot/src/share/vm/trace/trace.xml	Mon Jan 04 11:27:02 2016 +0100
@@ -465,6 +465,12 @@
       <value type="UTF8" field="name" label="Name" />
     </event>
 
+    <event id="AllocationRequiringGC" path="vm/gc/detailed/allocation_requiring_gc" label="Allocation Requiring GC"
+           has_thread="true" has_stacktrace="true"  is_instant="true">
+      <value type="UINT" field="gcId"  label="Pending GC ID" relation="GC_ID" />
+      <value type="BYTES64" field="size" label="Allocation Size" />
+    </event>
+
     <!-- Compiler events -->
 
     <event id="Compilation" path="vm/compiler/compilation" label="Compilation"