G1: Use SoftMaxHeapSize to guide GC heuristics

@@ -677,10 +677,13 @@
       (end_time_sec - _analytics->last_known_gc_end_time_sec()) * 1000.0;
     _analytics->update_recent_gc_times(end_time_sec, pause_time_ms);
     _analytics->compute_pause_time_ratio(interval_ms, pause_time_ms);
   }
 
+  if (collector_state()->finish_of_mixed_gc()) {
+    collector_state()->set_finish_of_mixed_gc(false);
+  }
   if (collector_state()->in_young_gc_before_mixed()) {
     assert(!this_pause_included_initial_mark, "The young GC before mixed is not allowed to be an initial mark GC");
     // This has been the young GC before we start doing mixed GCs. We already
     // decided to start mixed GCs much earlier, so there is nothing to do except
     // advancing the state.

@@ -690,10 +693,11 @@
     // This is a mixed GC. Here we decide whether to continue doing more
     // mixed GCs or not.
     if (!next_gc_should_be_mixed("continue mixed GCs",
                                  "do not continue mixed GCs")) {
       collector_state()->set_in_young_only_phase(true);
+      collector_state()->set_finish_of_mixed_gc(true);
 
       clear_collection_set_candidates();
       maybe_start_marking();
     }
   }

@@ -1409,5 +1413,12 @@
   // Don't clear the survivor list handles until the start of
   // the next evacuation pause - we need it in order to re-tag
   // the survivor regions from this evacuation pause as 'young'
   // at the start of the next.
 }
+
+size_t G1Policy::minimum_desired_bytes_after_concurrent_mark(size_t used_bytes) {
+  size_t minimum_desired_buffer_size = _ihop_control->predict_unstrained_buffer_size();
+  return minimum_desired_buffer_size != 0 ?
+           minimum_desired_buffer_size : _young_list_max_length * HeapRegion::GrainBytes
+         + _reserve_regions * HeapRegion::GrainBytes + used_bytes;
+}