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/shenandoah/heuristics/shenandoahAggressiveHeuristics.hpp"
  27 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
  28 #include "gc/shenandoah/shenandoahHeapRegion.hpp"
  29 #include "logging/log.hpp"
  30 #include "logging/logTag.hpp"
  31 #include "runtime/os.hpp"
  32 
  33 ShenandoahAggressiveHeuristics::ShenandoahAggressiveHeuristics() : ShenandoahHeuristics() {
  34   // Do not shortcut evacuation
  35   SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahImmediateThreshold, 100);
  36 
  37   // Aggressive runs with max speed for allocation, to capture races against mutator
  38   SHENANDOAH_ERGO_DISABLE_FLAG(ShenandoahPacing);
  39 
  40   // Aggressive evacuates everything, so it needs as much evac space as it can get
  41   SHENANDOAH_ERGO_ENABLE_FLAG(ShenandoahEvacReserveOverflow);
  42 
  43   // If class unloading is globally enabled, aggressive does unloading even with
  44   // concurrent cycles.
  45   if (ClassUnloading) {
  46     SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahUnloadClassesFrequency, 1);
  47   }
  48 }
  49 
  50 void ShenandoahAggressiveHeuristics::choose_collection_set_from_regiondata(ShenandoahCollectionSet* cset,
  51                                                                            RegionData* data, size_t size,
  52                                                                            size_t free) {
  53   for (size_t idx = 0; idx < size; idx++) {
  54     ShenandoahHeapRegion* r = data[idx]._region;
  55     if (r->garbage() > 0) {
  56       cset->add_region(r);
  57     }
  58   }
  59 }
  60 
  61 bool ShenandoahAggressiveHeuristics::should_start_normal_gc() const {
  62   log_info(gc)("Trigger: Start next cycle immediately");
  63   return true;
  64 }
  65 
  66 bool ShenandoahAggressiveHeuristics::should_process_references() {
  67   if (!can_process_references()) return false;
  68   // Randomly process refs with 50% chance.
  69   return (os::random() & 1) == 1;
  70 }
  71 
  72 bool ShenandoahAggressiveHeuristics::should_unload_classes() {
  73   if (!can_unload_classes_normal()) return false;
  74   if (has_metaspace_oom()) return true;
  75   // Randomly unload classes with 50% chance.
  76   return (os::random() & 1) == 1;
  77 }
  78 
  79 const char* ShenandoahAggressiveHeuristics::name() {
  80   return "aggressive";
  81 }
  82 
  83 bool ShenandoahAggressiveHeuristics::is_diagnostic() {
  84   return true;
  85 }
  86 
  87 bool ShenandoahAggressiveHeuristics::is_experimental() {
  88   return false;
  89 }