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

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

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

    snapshot.writCacheCountersHolder.pushData(holder);

    return holder;
  }
public WritCacheCountersHolder pushWriteCacheCounters(WritCacheCountersHolder holder) {
    if (snapshot == null)
      return holder;

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

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

    snapshot.writCacheCountersHolder.pushData(holder);

    return holder;
  }
Takes write cache 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 write cache may be <code>null</code>

@return Result of aggregation of performance data