1 /*
   2  * Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.
   3  * Copyright (c) 2017, Red Hat, Inc. and/or its affiliates.
   4  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   5  *
   6  * This code is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU General Public License version 2 only, as
   8  * published by the Free Software Foundation.
   9  *
  10  * This code is distributed in the hope that it will be useful, but WITHOUT
  11  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  12  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  13  * version 2 for more details (a copy is included in the LICENSE file that
  14  * accompanied this code).
  15  *
  16  * You should have received a copy of the GNU General Public License version
  17  * 2 along with this work; if not, write to the Free Software Foundation,
  18  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  19  *
  20  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  21  * or visit www.oracle.com if you need additional information or have any
  22  * questions.
  23  *
  24  */
  25 
  26 #include "precompiled.hpp"
  27 #include "gc/shared/gcArguments.hpp"
  28 #include "runtime/arguments.hpp"
  29 #include "runtime/globals.hpp"
  30 #include "runtime/globals_extension.hpp"
  31 #include "utilities/macros.hpp"
  32 
  33 void GCArguments::initialize() {
  34   if (FullGCALot && FLAG_IS_DEFAULT(MarkSweepAlwaysCompactCount)) {
  35     MarkSweepAlwaysCompactCount = 1;  // Move objects every gc.
  36   }
  37 
  38   if (!(UseParallelGC || UseParallelOldGC) && FLAG_IS_DEFAULT(ScavengeBeforeFullGC)) {
  39     FLAG_SET_DEFAULT(ScavengeBeforeFullGC, false);
  40   }
  41 
  42   if (GCTimeLimit == 100) {
  43     // Turn off gc-overhead-limit-exceeded checks
  44     FLAG_SET_DEFAULT(UseGCOverheadLimit, false);
  45   }
  46 
  47   if (MinHeapFreeRatio == 100) {
  48     // Keeping the heap 100% free is hard ;-) so limit it to 99%.
  49     FLAG_SET_ERGO(uintx, MinHeapFreeRatio, 99);
  50   }
  51 
  52   if (!ClassUnloading) {
  53     // If class unloading is disabled, also disable concurrent class unloading.
  54     FLAG_SET_CMDLINE(bool, ClassUnloadingWithConcurrentMark, false);
  55   }
  56 }