--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/shenandoah/heuristics/shenandoahPassiveHeuristics.cpp	Mon Dec 10 15:47:44 2018 +0100
@@ -0,0 +1,117 @@
+/*
+ * Copyright (c) 2018, Red Hat, Inc. All rights reserved.
+ *
+ * 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 "gc/shenandoah/heuristics/shenandoahPassiveHeuristics.hpp"
+#include "gc/shenandoah/shenandoahCollectionSet.hpp"
+#include "gc/shenandoah/shenandoahHeapRegion.hpp"
+#include "logging/log.hpp"
+#include "logging/logTag.hpp"
+
+ShenandoahPassiveHeuristics::ShenandoahPassiveHeuristics() : ShenandoahHeuristics() {
+  // Do not allow concurrent cycles.
+  FLAG_SET_DEFAULT(ExplicitGCInvokesConcurrent, false);
+  FLAG_SET_DEFAULT(ShenandoahImplicitGCInvokesConcurrent, false);
+
+  // Passive runs with max speed, reacts on allocation failure.
+  FLAG_SET_DEFAULT(ShenandoahPacing, false);
+
+  // No need for evacuation reserve with Full GC, only for Degenerated GC.
+  if (!ShenandoahDegeneratedGC) {
+    SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahEvacReserve, 0);
+  }
+
+  // Disable known barriers by default.
+  SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahSATBBarrier);
+  SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahKeepAliveBarrier);
+  SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahWriteBarrier);
+  SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahReadBarrier);
+  SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahStoreValEnqueueBarrier);
+  SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahStoreValReadBarrier);
+  SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahCASBarrier);
+  SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahAcmpBarrier);
+  SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahCloneBarrier);
+
+  // Final configuration checks
+  // No barriers are required to run.
+}
+
+bool ShenandoahPassiveHeuristics::should_start_normal_gc() const {
+  // Never do concurrent GCs.
+  return false;
+}
+
+bool ShenandoahPassiveHeuristics::should_process_references() {
+  // Always process references, if we can.
+  return can_process_references();
+}
+
+bool ShenandoahPassiveHeuristics::should_unload_classes() {
+  // Always unload classes, if we can.
+  return can_unload_classes();
+}
+
+bool ShenandoahPassiveHeuristics::should_degenerate_cycle() {
+  // Always fail to Degenerated GC, if enabled
+  return ShenandoahDegeneratedGC;
+}
+
+void ShenandoahPassiveHeuristics::choose_collection_set_from_regiondata(ShenandoahCollectionSet* cset,
+                                                                        RegionData* data, size_t size,
+                                                                        size_t actual_free) {
+  assert(ShenandoahDegeneratedGC, "This path is only taken for Degenerated GC");
+
+  // Do not select too large CSet that would overflow the available free space.
+  // Take at least the entire evacuation reserve, and be free to overflow to free space.
+  size_t capacity  = ShenandoahHeap::heap()->capacity();
+  size_t available = MAX2(ShenandoahEvacReserve * capacity / 100, actual_free);
+  size_t max_cset  = (size_t)(available / ShenandoahEvacWaste);
+
+  log_info(gc, ergo)("CSet Selection. Actual Free: " SIZE_FORMAT "M, Max CSet: " SIZE_FORMAT "M",
+                     actual_free / M, max_cset / M);
+
+  size_t threshold = ShenandoahHeapRegion::region_size_bytes() * ShenandoahGarbageThreshold / 100;
+
+  size_t live_cset = 0;
+  for (size_t idx = 0; idx < size; idx++) {
+    ShenandoahHeapRegion* r = data[idx]._region;
+    size_t new_cset = live_cset + r->get_live_data_bytes();
+    if (new_cset < max_cset && r->garbage() > threshold) {
+      live_cset = new_cset;
+      cset->add_region(r);
+    }
+  }
+}
+
+const char* ShenandoahPassiveHeuristics::name() {
+  return "passive";
+}
+
+bool ShenandoahPassiveHeuristics::is_diagnostic() {
+  return true;
+}
+
+bool ShenandoahPassiveHeuristics::is_experimental() {
+  return false;
+}