--- a/hotspot/src/share/vm/gc_implementation/shared/vmGCOperations.cpp	Mon Jul 07 12:37:11 2014 +0200
+++ b/hotspot/src/share/vm/gc_implementation/shared/vmGCOperations.cpp	Mon Jul 07 10:12:40 2014 +0200
@@ -195,6 +195,43 @@
   gch->do_full_collection(gch->must_clear_all_soft_refs(), _max_level);
 }
 
+bool VM_CollectForMetadataAllocation::initiate_concurrent_GC() {
+#if INCLUDE_ALL_GCS
+  if (UseConcMarkSweepGC || UseG1GC) {
+    if (UseConcMarkSweepGC && CMSClassUnloadingEnabled) {
+      MetaspaceGC::set_should_concurrent_collect(true);
+    } else if (UseG1GC) {
+      G1CollectedHeap* g1h = G1CollectedHeap::heap();
+      g1h->g1_policy()->set_initiate_conc_mark_if_possible();
+
+      GCCauseSetter x(g1h, _gc_cause);
+
+      // At this point we are supposed to start a concurrent cycle. We
+      // will do so if one is not already in progress.
+      bool should_start = g1h->g1_policy()->force_initial_mark_if_outside_cycle(_gc_cause);
+
+      if (should_start) {
+        double pause_target = g1h->g1_policy()->max_pause_time_ms();
+        g1h->do_collection_pause_at_safepoint(pause_target);
+      }
+    }
+
+    return true;
+  }
+#endif
+  return false;
+}
+
+static void log_metaspace_alloc_failure_for_concurrent_GC() {
+  if (Verbose && PrintGCDetails) {
+    if (UseConcMarkSweepGC) {
+      gclog_or_tty->print_cr("\nCMS full GC for Metaspace");
+    } else if (UseG1GC) {
+      gclog_or_tty->print_cr("\nG1 full GC for Metaspace");
+    }
+  }
+}
+
 void VM_CollectForMetadataAllocation::doit() {
   SvcGCMarker sgcm(SvcGCMarker::FULL);
 
@@ -206,54 +243,57 @@
   // a GC that freed space for the allocation.
   if (!MetadataAllocationFailALot) {
     _result = _loader_data->metaspace_non_null()->allocate(_size, _mdtype);
-  }
-
-  if (_result == NULL) {
-    if (UseConcMarkSweepGC) {
-      if (CMSClassUnloadingEnabled) {
-        MetaspaceGC::set_should_concurrent_collect(true);
-      }
-      // For CMS expand since the collection is going to be concurrent.
-      _result =
-        _loader_data->metaspace_non_null()->expand_and_allocate(_size, _mdtype);
-    }
-    if (_result == NULL) {
-      // Don't clear the soft refs yet.
-      if (Verbose && PrintGCDetails && UseConcMarkSweepGC) {
-        gclog_or_tty->print_cr("\nCMS full GC for Metaspace");
-      }
-      heap->collect_as_vm_thread(GCCause::_metadata_GC_threshold);
-      // After a GC try to allocate without expanding.  Could fail
-      // and expansion will be tried below.
-      _result =
-        _loader_data->metaspace_non_null()->allocate(_size, _mdtype);
-    }
-    if (_result == NULL) {
-      // If still failing, allow the Metaspace to expand.
-      // See delta_capacity_until_GC() for explanation of the
-      // amount of the expansion.
-      // This should work unless there really is no more space
-      // or a MaxMetaspaceSize has been specified on the command line.
-      _result =
-        _loader_data->metaspace_non_null()->expand_and_allocate(_size, _mdtype);
-      if (_result == NULL) {
-        // If expansion failed, do a last-ditch collection and try allocating
-        // again.  A last-ditch collection will clear softrefs.  This
-        // behavior is similar to the last-ditch collection done for perm
-        // gen when it was full and a collection for failed allocation
-        // did not free perm gen space.
-        heap->collect_as_vm_thread(GCCause::_last_ditch_collection);
-        _result =
-          _loader_data->metaspace_non_null()->allocate(_size, _mdtype);
-      }
-    }
-    if (Verbose && PrintGCDetails && _result == NULL) {
-      gclog_or_tty->print_cr("\nAfter Metaspace GC failed to allocate size "
-                             SIZE_FORMAT, _size);
+    if (_result != NULL) {
+      return;
     }
   }
 
-  if (_result == NULL && GC_locker::is_active_and_needs_gc()) {
+  if (initiate_concurrent_GC()) {
+    // For CMS and G1 expand since the collection is going to be concurrent.
+    _result = _loader_data->metaspace_non_null()->expand_and_allocate(_size, _mdtype);
+    if (_result != NULL) {
+      return;
+    }
+
+    log_metaspace_alloc_failure_for_concurrent_GC();
+  }
+
+  // Don't clear the soft refs yet.
+  heap->collect_as_vm_thread(GCCause::_metadata_GC_threshold);
+  // After a GC try to allocate without expanding.  Could fail
+  // and expansion will be tried below.
+  _result = _loader_data->metaspace_non_null()->allocate(_size, _mdtype);
+  if (_result != NULL) {
+    return;
+  }
+
+  // If still failing, allow the Metaspace to expand.
+  // See delta_capacity_until_GC() for explanation of the
+  // amount of the expansion.
+  // This should work unless there really is no more space
+  // or a MaxMetaspaceSize has been specified on the command line.
+  _result = _loader_data->metaspace_non_null()->expand_and_allocate(_size, _mdtype);
+  if (_result != NULL) {
+    return;
+  }
+
+  // If expansion failed, do a last-ditch collection and try allocating
+  // again.  A last-ditch collection will clear softrefs.  This
+  // behavior is similar to the last-ditch collection done for perm
+  // gen when it was full and a collection for failed allocation
+  // did not free perm gen space.
+  heap->collect_as_vm_thread(GCCause::_last_ditch_collection);
+  _result = _loader_data->metaspace_non_null()->allocate(_size, _mdtype);
+  if (_result != NULL) {
+    return;
+  }
+
+  if (Verbose && PrintGCDetails) {
+    gclog_or_tty->print_cr("\nAfter Metaspace GC failed to allocate size "
+                           SIZE_FORMAT, _size);
+  }
+
+  if (GC_locker::is_active_and_needs_gc()) {
     set_gc_locked();
   }
 }