core/src/main/java/com/orientechnologies/orient/core/storage/impl/local/statistic/OSessionStoragePerformanceStatistic.java
public StorageCountersHolder pushStorageCounters(StorageCountersHolder holder) {
    if (snapshot == null)
      return holder;

    if (snapshot.storageCountersHolder == null)
      return holder;

    if (holder == null)
      holder = new StorageCountersHolder();

    snapshot.storageCountersHolder.pushData(holder);

    return holder;
  }
public StorageCountersHolder pushStorageCounters(StorageCountersHolder holder) {
    if (snapshot == null)
      return holder;

    if (snapshot.storageCountersHolder == null)
      return holder;

    if (holder == null)
      holder = new StorageCountersHolder();

    snapshot.storageCountersHolder.pushData(holder);

    return holder;
  }
Takes storage performance data from last snapshot and aggregates them with data passed inside method as parameter. Result of
aggregation of performance data is returned inside of passed in performance data and as result of this method call.

@param holder Performance data for storage may be <code>null</code>

@return Result of aggregation of performance data