Java 8完整GC和OutOfMemory Java堆空间

3 回答

• 0

  显然，创建的某些对象无法正确收集垃圾 . 您可以尝试使用VisualVM的采样器功能并跟踪创建的实例数 .

  回复于 2024-04-24T11:37:57+08:00
• 0

  尝试使用MapDB缓存IO操作 .

  您可以这样做将其缓存到基于磁盘的文件数据库：

  import java.io.File;
  import java.io.IOException;
  import java.util.Map;
  import org.mapdb.DB;
  import org.mapdb.DBMaker;
  
  /**
   * Singleton class.
   */
  public class DBManager 
  {
          /**
       * Variables.
       */
      private static File dbFile = new File("path/to/file");
      private DB db;
      private static final String password = "yourPassword";
      private Map<Integer, String> ctDB;
      private static DBManager manager;
  
     /**
      * Singleton operations.
      */
  
    /**
     * Static initializer.
     */
    static
    {
       manager = null;
    }
  
  /**
   * Singleton method @see DBManager.getInstance(File dbFile);
   * @return          ->  An object / instance of this class.
   */
  public static DBManager getInstance()
  {       
      if(isFileDatabaseOK())
      {
          /**
           * Check if an object/instance from this class exists already. 
           */
          if(manager == null)
          {
              manager = new DBManager();
          }
  
          /**
           * Return an object/instance of this class.
           */
          return manager;
      }
      else
      {
          return null;
      }
  }
  
  /**
   * Constructors.
   */
  
  /**
   * Empty default Constructor starts the MapDB instance.
   */
  private DBManager() 
  {       
      /**
       * Load the database file from the given path
       * and initialize the database.
       */
      initMapDB();
  }
  
  /**
   * MapDB initializer.
   */
  
  /**
   * Initialize a MapDB database.
   */
  private void initMapDB() 
  {
      /**
       * Persistence: Make MapDB able to load the same database from the 
       * file after JVM-Shutdown. Initialize database without @see     org.mapdb.DBMaker.deleteFilesAfterClose()
       * @see <link>https://groups.google.com/forum/#!topic/mapdb/AW8Ax49TLUc</link>
       */
      db = DBMaker.newFileDB(dbFile)
              .closeOnJvmShutdown()       
              .asyncWriteDisable()
              .encryptionEnable(password.getBytes())
              .make();
  
      /**
       * Create a Map / Get the existing map.
       */
      ctDB = db.getTreeMap("database");
  }
  
  /**
   * File existence check.
   * If file doesn't exists -> Create a new db file and inform the user.
   */
  private static boolean isFileDatabaseOK() 
  {       
      /**
       * If the file doesn't exists (First run) create a new file and 
       * inform the user.
       */
      if(!dbFile.exists())
      {
          try 
          {
              dbFile.getParentFile().mkdirs();
              dbFile.createNewFile();
  
              /**
               * TODO 
               * System.out.println("Database not found. Creating a new one.");
               */
  
              return true;
          }
          catch (IOException e)
          {
              /**
               * TODO Error handling
               */
              e.printStackTrace();
              return false;
          }
      }
      else
      {           
          return true;
      }
  }
  
  /**
   * Database methods / operations.
   */
  
  /**
   * Get objects by id.
   * @param id    ->  Search parameter.
   * @return      ->  The object that belongs to the id.
   */
  public String get(int id) 
  {
      return ctDB.get(id);
  }
  
  /**
   * Adding objects to the database.
   * @param id -> The key reference to the object as 'id'.
   * @param object -> The object to cache.
   */
  public void put(int id, String object)
  {
      ctDB.put(id, object);
  
      db.commit();
  }
  }
  

  然后做：

  DBManager manager = DBManager.getInstance();
   manager.put(1, "test");
   Sytem.out.println(manger.get(1));
  

  回复于 2024-04-24T11:37:57+08:00
• 1

  如果为大多数参数设置默认值，G1GC运行良好 . 仅设置关键参数

  -XX:MaxGCPauseMillis
  -XX:G1HeapRegionSize
  -XX:ParallelGCThreads
  -XX:ConcGCThreads
  

  并将其他所有内容留给Java .

  您可以在以下帖子中找到更多详细信息：

  Java 7 (JDK 7) garbage collection and documentation on G1

  Why do I get OutOfMemory when 20% of the heap is still free?

  使用一些内存分析器工具，如mat来了解根本原因 .

  在你的情况下，很明显oldgen正在成长 . 检查可能的内存泄漏 . 如果没有发现内存泄漏，请进一步增加堆内存 .

  回复于 2024-04-24T11:37:57+08:00