g1CollectionSetChooser.hpp

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#ifndef SHARE_GC_G1_G1COLLECTIONSETCHOOSER_HPP
#define SHARE_GC_G1_G1COLLECTIONSETCHOOSER_HPP

#include "gc/g1/heapRegion.hpp"
#include "memory/allocation.hpp"
#include "runtime/globals.hpp"

class G1CollectionSetCandidates;
class WorkGang;

// Helper class to calculate collection set candidates, and containing some related
// methods.
class G1CollectionSetChooser : public AllStatic {
  static uint calculate_work_chunk_size(uint num_workers, uint num_regions);

  // Remove regions in the collection set candidates as long as the G1HeapWastePercent
  // criteria is met. Keep at least the minimum amount of old regions to guarantee
  // some progress.
  static void prune(G1CollectionSetCandidates* candidates);
public:

  static size_t mixed_gc_live_threshold_bytes() {
    return HeapRegion::GrainBytes * (size_t) G1MixedGCLiveThresholdPercent / 100;
  }

  static bool region_occupancy_low_enough_for_evac(size_t live_bytes) {
    return live_bytes < mixed_gc_live_threshold_bytes();
  }

  // Determine whether to add the given region to the collection set candidates or
  // not. Currently, we skip pinned regions and regions whose live
  // bytes are over the threshold. Humongous regions may be reclaimed during cleanup.
  // Regions also need a complete remembered set to be a candidate.
  static bool should_add(HeapRegion* hr);

  // Build and return set of collection set candidates sorted by decreasing gc
  // efficiency.
  static G1CollectionSetCandidates* build(WorkGang* workers, uint max_num_regions);
};

#endif // SHARE_GC_G1_G1COLLECTIONSETCHOOSER_HPP