1 /*
   2  * Copyright (c) 2018, 2019, Red Hat, Inc. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 
  27 #include "gc/shenandoah/heuristics/shenandoahAggressiveHeuristics.hpp"
  28 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
  29 #include "gc/shenandoah/shenandoahHeapRegion.hpp"
  30 #include "logging/log.hpp"
  31 #include "logging/logTag.hpp"
  32 #include "runtime/os.hpp"
  33 
  34 ShenandoahAggressiveHeuristics::ShenandoahAggressiveHeuristics() : ShenandoahHeuristics() {
  35   // Do not shortcut evacuation
  36   SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahImmediateThreshold, 100);
  37 
  38   // Aggressive evacuates everything, so it needs as much evac space as it can get
  39   SHENANDOAH_ERGO_ENABLE_FLAG(ShenandoahEvacReserveOverflow);
  40 
  41   // If class unloading is globally enabled, aggressive does unloading even with
  42   // concurrent cycles.
  43   if (ClassUnloading) {
  44     SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahUnloadClassesFrequency, 1);
  45   }
  46 }
  47 
  48 void ShenandoahAggressiveHeuristics::choose_collection_set_from_regiondata(ShenandoahCollectionSet* cset,
  49                                                                            RegionData* data, size_t size,
  50                                                                            size_t free) {
  51   for (size_t idx = 0; idx < size; idx++) {
  52     ShenandoahHeapRegion* r = data[idx]._region;
  53     if (r->garbage() > 0) {
  54       cset->add_region(r);
  55     }
  56   }
  57 }
  58 
  59 bool ShenandoahAggressiveHeuristics::should_start_gc() const {
  60   log_info(gc)("Trigger: Start next cycle immediately");
  61   return true;
  62 }
  63 
  64 bool ShenandoahAggressiveHeuristics::should_process_references() {
  65   if (!can_process_references()) return false;
  66   // Randomly process refs with 50% chance.
  67   return (os::random() & 1) == 1;
  68 }
  69 
  70 bool ShenandoahAggressiveHeuristics::should_unload_classes() {
  71   if (!can_unload_classes_normal()) return false;
  72   if (has_metaspace_oom()) return true;
  73   // Randomly unload classes with 50% chance.
  74   return (os::random() & 1) == 1;
  75 }
  76 
  77 const char* ShenandoahAggressiveHeuristics::name() {
  78   return "aggressive";
  79 }
  80 
  81 bool ShenandoahAggressiveHeuristics::is_diagnostic() {
  82   return true;
  83 }
  84 
  85 bool ShenandoahAggressiveHeuristics::is_experimental() {
  86   return false;
  87 }