src/hotspot/share/gc/shared/stringdedup/stringDedupProcessor.hpp

/*
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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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#ifndef SHARE_GC_SHARED_STRINGDEDUP_STRINGDEDUPPROCESSOR_HPP
#define SHARE_GC_SHARED_STRINGDEDUP_STRINGDEDUPPROCESSOR_HPP

#include "gc/shared/stringdedup/stringDedup.hpp"
#include "memory/allocation.hpp"
#include "utilities/macros.hpp"

class JavaThread;
class OopStorage;

// This class performs string deduplication.  There is only one instance of
// this class.  It processes deduplication requests.  It also manages the
// deduplication table, performing resize and cleanup operations as needed.
// This includes managing the OopStorage objects used to hold requests.
//
// Processing periodically checks for and yields at safepoints.  Processing of
// requests is performed in incremental chunks.  The Table provides
// incremental operations for resizing and for removing dead entries, so
// safepoint checks can be performed between steps in those operations.
class StringDedup::Processor : public CHeapObj<mtGC> {
  Processor();
  ~Processor() = default;

  NONCOPYABLE(Processor);

  static OopStorage* _storages[2];
  static StorageUse* volatile _storage_for_requests;
  static StorageUse* _storage_for_processing;

  JavaThread* _thread;

  // Wait until there are requests to be processed.  The storage for requests
  // and storage for processing are swapped; the former requests storage
  // becomes the current processing storage, and vice versa.
  // precondition: the processing storage is empty.
  void wait_for_requests() const;

  // Yield if requested.
  void yield() const;

  class ProcessRequest;
  void process_requests() const;
  void cleanup_table(bool grow_only, bool force) const;

  void log_statistics();

public:
  static void initialize();

  static void initialize_storage();
  static StorageUse* storage_for_requests();

  // Use thread as the deduplication thread.
  // precondition: thread == Thread::current()
  void run(JavaThread* thread);
};

#endif // SHARE_GC_SHARED_STRINGDEDUP_STRINGDEDUPPROCESSOR_HPP