shenandoahAggressiveHeuristics.cpp

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * version 2 for more details (a copy is included in the LICENSE file that
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 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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#include "precompiled.hpp"

#include "gc/shenandoah/heuristics/shenandoahAggressiveHeuristics.hpp"
#include "gc/shenandoah/shenandoahCollectionSet.hpp"
#include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
#include "logging/log.hpp"
#include "logging/logTag.hpp"
#include "runtime/os.hpp"

ShenandoahAggressiveHeuristics::ShenandoahAggressiveHeuristics() : ShenandoahHeuristics() {
  // Do not shortcut evacuation
  SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahImmediateThreshold, 100);

  // Aggressive evacuates everything, so it needs as much evac space as it can get
  SHENANDOAH_ERGO_ENABLE_FLAG(ShenandoahEvacReserveOverflow);

  // If class unloading is globally enabled, aggressive does unloading even with
  // concurrent cycles.
  if (ClassUnloading) {
    SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahUnloadClassesFrequency, 1);
  }
}

void ShenandoahAggressiveHeuristics::choose_collection_set_from_regiondata(ShenandoahCollectionSet* cset,
                                                                           RegionData* data, size_t size,
                                                                           size_t free) {
  for (size_t idx = 0; idx < size; idx++) {
    ShenandoahHeapRegion* r = data[idx]._region;
    if (r->garbage() > 0) {
      cset->add_region(r);
    }
  }
}

bool ShenandoahAggressiveHeuristics::should_start_gc() {
  log_info(gc)("Trigger: Start next cycle immediately");
  return true;
}

bool ShenandoahAggressiveHeuristics::should_unload_classes() {
  if (!can_unload_classes_normal()) return false;
  if (has_metaspace_oom()) return true;
  // Randomly unload classes with 50% chance.
  return (os::random() & 1) == 1;
}