src/hotspot/share/gc/shenandoah/heuristics/shenandoahCompactHeuristics.cpp

/*
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#include "gc/shenandoah/heuristics/shenandoahCompactHeuristics.hpp"
#include "gc/shenandoah/shenandoahCollectionSet.hpp"
#include "gc/shenandoah/shenandoahFreeSet.hpp"
#include "gc/shenandoah/shenandoahHeap.inline.hpp"
#include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
#include "logging/log.hpp"
#include "logging/logTag.hpp"

ShenandoahCompactHeuristics::ShenandoahCompactHeuristics(ShenandoahSpaceInfo* space_info) :
  ShenandoahHeuristics(space_info) {
  SHENANDOAH_ERGO_ENABLE_FLAG(ExplicitGCInvokesConcurrent);
  SHENANDOAH_ERGO_ENABLE_FLAG(ShenandoahImplicitGCInvokesConcurrent);
  SHENANDOAH_ERGO_ENABLE_FLAG(ShenandoahUncommit);
  SHENANDOAH_ERGO_ENABLE_FLAG(ShenandoahAlwaysClearSoftRefs);
  SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahAllocationThreshold,  10);
  SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahImmediateThreshold,   100);
  SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahUncommitDelay,        1000);
  SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahGuaranteedGCInterval, 30000);
  SHENANDOAH_ERGO_OVERRIDE_DEFAULT(ShenandoahGarbageThreshold,     10);
}

bool ShenandoahCompactHeuristics::should_start_gc() {
  size_t max_capacity = _space_info->max_capacity();
  size_t capacity = _space_info->soft_max_capacity();
  size_t available = _space_info->available();

  // Make sure the code below treats available without the soft tail.
  size_t soft_tail = max_capacity - capacity;
  available = (available > soft_tail) ? (available - soft_tail) : 0;

  size_t threshold_bytes_allocated = capacity / 100 * ShenandoahAllocationThreshold;
  size_t min_threshold = capacity / 100 * ShenandoahMinFreeThreshold;

  if (available < min_threshold) {
    log_trigger("Free (%zu%s) is below minimum threshold (%zu%s)",
                byte_size_in_proper_unit(available),     proper_unit_for_byte_size(available),
                byte_size_in_proper_unit(min_threshold), proper_unit_for_byte_size(min_threshold));
    accept_trigger();
    return true;
  }

  size_t bytes_allocated = _space_info->bytes_allocated_since_gc_start();
  if (bytes_allocated > threshold_bytes_allocated) {
    log_trigger("Allocated since last cycle (%zu%s) is larger than allocation threshold (%zu%s)",
                byte_size_in_proper_unit(bytes_allocated),           proper_unit_for_byte_size(bytes_allocated),
                byte_size_in_proper_unit(threshold_bytes_allocated), proper_unit_for_byte_size(threshold_bytes_allocated));
    accept_trigger();
    return true;
  }

  return ShenandoahHeuristics::should_start_gc();
}

void ShenandoahCompactHeuristics::choose_collection_set_from_regiondata(ShenandoahCollectionSet* cset,
                                                                        RegionData* data, size_t size,
                                                                        size_t actual_free) {
  // Do not select too large CSet that would overflow the available free space
  size_t max_cset = actual_free * 3 / 4;

  log_info(gc, ergo)("CSet Selection. Actual Free: %zu%s, Max CSet: %zu%s",
                     byte_size_in_proper_unit(actual_free), proper_unit_for_byte_size(actual_free),
                     byte_size_in_proper_unit(max_cset),    proper_unit_for_byte_size(max_cset));

  size_t threshold = ShenandoahHeapRegion::region_size_bytes() * ShenandoahGarbageThreshold / 100;

  size_t live_cset = 0;
  for (size_t idx = 0; idx < size; idx++) {
    ShenandoahHeapRegion* r = data[idx].get_region();
    size_t new_cset = live_cset + r->get_live_data_bytes();
    if (new_cset < max_cset && r->garbage() > threshold) {
      live_cset = new_cset;
      cset->add_region(r);
    }
  }
}