1 /*
   2  * Copyright (c) 2018, Red Hat, Inc. All rights reserved.
   3  *
   4  * This code is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU General Public License version 2 only, as
   6  * published by the Free Software Foundation.
   7  *
   8  * This code is distributed in the hope that it will be useful, but WITHOUT
   9  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  10  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  11  * version 2 for more details (a copy is included in the LICENSE file that
  12  * accompanied this code).
  13  *
  14  * You should have received a copy of the GNU General Public License version
  15  * 2 along with this work; if not, write to the Free Software Foundation,
  16  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  17  *
  18  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  19  * or visit www.oracle.com if you need additional information or have any
  20  * questions.
  21  *
  22  */
  23 
  24 #include "precompiled.hpp"
  25 
  26 #include "gc_implementation/shenandoah/heuristics/shenandoahAggressiveHeuristics.hpp"
  27 #include "gc_implementation/shenandoah/shenandoahCollectionSet.hpp"
  28 #include "gc_implementation/shenandoah/shenandoahHeapRegion.inline.hpp"
  29 #include "gc_implementation/shenandoah/shenandoahLogging.hpp"
  30 #include "runtime/os.hpp"
  31 
  32 ShenandoahAggressiveHeuristics::ShenandoahAggressiveHeuristics() : ShenandoahHeuristics() {
  33   // Do not shortcut evacuation
  34   SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahImmediateThreshold, 100);
  35 
  36   // Aggressive evacuates everything, so it needs as much evac space as it can get
  37   SHENANDOAH_ERGO_ENABLE_FLAG(ShenandoahEvacReserveOverflow);
  38 
  39   // If class unloading is globally enabled, aggressive does unloading even with
  40   // concurrent cycles.
  41   if (ClassUnloading) {
  42     SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahUnloadClassesFrequency, 1);
  43   }
  44 }
  45 
  46 void ShenandoahAggressiveHeuristics::choose_collection_set_from_regiondata(ShenandoahCollectionSet* cset,
  47                                                                            RegionData* data, size_t size,
  48                                                                            size_t free) {
  49   for (size_t idx = 0; idx < size; idx++) {
  50     ShenandoahHeapRegion* r = data[idx]._region;
  51     if (r->garbage() > 0) {
  52       cset->add_region(r);
  53     }
  54   }
  55 }
  56 
  57 bool ShenandoahAggressiveHeuristics::should_start_gc() const {
  58   log_info(gc)("Trigger: Start next cycle immediately");
  59   return true;
  60 }
  61 
  62 bool ShenandoahAggressiveHeuristics::should_process_references() {
  63   if (!can_process_references()) return false;
  64   // Randomly process refs with 50% chance.
  65   return (os::random() & 1) == 1;
  66 }
  67 
  68 bool ShenandoahAggressiveHeuristics::should_unload_classes() {
  69   if (!can_unload_classes_normal()) return false;
  70   if (has_metaspace_oom()) return true;
  71   // Randomly unload classes with 50% chance.
  72   return (os::random() & 1) == 1;
  73 }