8022872: G1: Use correct GC cause for young GC triggered by humongous allocations

Reviewed-by: tonyp, tschatzl

hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp

@@ -981,7 +981,8 @@ HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
 
     if (should_try_gc) {
       bool succeeded;
-      result = do_collection_pause(word_size, gc_count_before, &succeeded);
+      result = do_collection_pause(word_size, gc_count_before, &succeeded,
+          GCCause::_g1_inc_collection_pause);
       if (result != NULL) {
         assert(succeeded, "only way to get back a non-NULL result");
         return result;
@@ -1106,7 +1107,8 @@ HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
       // enough space for the allocation to succeed after the pause.
 
       bool succeeded;
-      result = do_collection_pause(word_size, gc_count_before, &succeeded);
+      result = do_collection_pause(word_size, gc_count_before, &succeeded,
+          GCCause::_g1_humongous_allocation);
       if (result != NULL) {
         assert(succeeded, "only way to get back a non-NULL result");
         return result;
@@ -3700,14 +3702,15 @@ void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
 
 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
                                                unsigned int gc_count_before,
-                                               bool* succeeded) {
+                                               bool* succeeded,
+                                               GCCause::Cause gc_cause) {
   assert_heap_not_locked_and_not_at_safepoint();
   g1_policy()->record_stop_world_start();
   VM_G1IncCollectionPause op(gc_count_before,
                              word_size,
                              false, /* should_initiate_conc_mark */
                              g1_policy()->max_pause_time_ms(),
-                             GCCause::_g1_inc_collection_pause);
+                             gc_cause);
   VMThread::execute(&op);
 
   HeapWord* result = op.result();

hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp

@@ -776,9 +776,10 @@ protected:
   // it has to be read while holding the Heap_lock. Currently, both
   // methods that call do_collection_pause() release the Heap_lock
   // before the call, so it's easy to read gc_count_before just before.
-  HeapWord* do_collection_pause(size_t       word_size,
-                                unsigned int gc_count_before,
-                                bool*        succeeded);
+  HeapWord* do_collection_pause(size_t         word_size,
+                                unsigned int   gc_count_before,
+                                bool*          succeeded,
+                                GCCause::Cause gc_cause);
 
   // The guts of the incremental collection pause, executed by the vm
   // thread. It returns false if it is unable to do the collection due

hotspot/src/share/vm/gc_implementation/g1/vm_operations_g1.cpp

@@ -70,9 +70,6 @@ VM_G1IncCollectionPause::VM_G1IncCollectionPause(
   guarantee(target_pause_time_ms > 0.0,
             err_msg("target_pause_time_ms = %1.6lf should be positive",
                     target_pause_time_ms));
-  guarantee(word_size == 0 || gc_cause == GCCause::_g1_inc_collection_pause,
-            "we can only request an allocation if the GC cause is for "
-            "an incremental GC pause");
   _gc_cause = gc_cause;
 }