--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/shared/gcOverheadChecker.cpp	Tue Jan 15 15:59:47 2019 -0800
@@ -0,0 +1,102 @@
+/*
+ * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2019, Google and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * 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/shared/gcOverheadChecker.hpp"
+#include "gc/shared/softRefPolicy.hpp"
+#include "logging/log.hpp"
+
+GCOverheadChecker::GCOverheadChecker() :
+  _gc_overhead_limit_exceeded(false),
+  _print_gc_overhead_limit_would_be_exceeded(false),
+  _gc_overhead_limit_count(0) {
+  assert(GCOverheadLimitThreshold > 0,
+    "No opportunity to clear SoftReferences before GC overhead limit");
+}
+
+void GCOverheadChecker::check_gc_overhead_limit(GCOverheadTester* time_overhead,
+                                                GCOverheadTester* space_overhead,
+                                                bool is_full_gc,
+                                                GCCause::Cause gc_cause,
+                                                SoftRefPolicy* soft_ref_policy) {
+
+  // Ignore explicit GC's.  Exiting here does not set the flag and
+  // does not reset the count.
+  if (GCCause::is_user_requested_gc(gc_cause) ||
+      GCCause::is_serviceability_requested_gc(gc_cause)) {
+    return;
+  }
+
+  bool print_gc_overhead_limit_would_be_exceeded = false;
+  if (is_full_gc) {
+    if (time_overhead->is_exceeded() && space_overhead->is_exceeded()) {
+      // Collections, on average, are taking too much time, and
+      // we have too little space available after a full gc.
+      // At this point the GC overhead limit is being exceeded.
+      _gc_overhead_limit_count++;
+      if (UseGCOverheadLimit) {
+        if (_gc_overhead_limit_count >= GCOverheadLimitThreshold){
+          // All conditions have been met for throwing an out-of-memory
+          set_gc_overhead_limit_exceeded(true);
+          // Avoid consecutive OOM due to the gc time limit by resetting
+          // the counter.
+          reset_gc_overhead_limit_count();
+        } else {
+          // The required consecutive collections which exceed the
+          // GC time limit may or may not have been reached. We
+          // are approaching that condition and so as not to
+          // throw an out-of-memory before all SoftRef's have been
+          // cleared, set _should_clear_all_soft_refs in CollectorPolicy.
+          // The clearing will be done on the next GC.
+          bool near_limit = gc_overhead_limit_near();
+          if (near_limit) {
+            soft_ref_policy->set_should_clear_all_soft_refs(true);
+            log_trace(gc, ergo)("Nearing GC overhead limit, will be clearing all SoftReference");
+          }
+        }
+      }
+      // Set this even when the overhead limit will not
+      // cause an out-of-memory.  Diagnostic message indicating
+      // that the overhead limit is being exceeded is sometimes
+      // printed.
+      print_gc_overhead_limit_would_be_exceeded = true;
+
+    } else {
+      // Did not exceed overhead limits
+      reset_gc_overhead_limit_count();
+    }
+  }
+
+  if (UseGCOverheadLimit) {
+    if (gc_overhead_limit_exceeded()) {
+      log_trace(gc, ergo)("GC is exceeding overhead limit of " UINTX_FORMAT "%%", GCTimeLimit);
+      reset_gc_overhead_limit_count();
+    } else if (print_gc_overhead_limit_would_be_exceeded) {
+      assert(_gc_overhead_limit_count > 0, "Should not be printing");
+      log_trace(gc, ergo)("GC would exceed overhead limit of " UINTX_FORMAT "%% %d consecutive time(s)",
+                          GCTimeLimit, _gc_overhead_limit_count);
+    }
+  }
+}