public long getUsedMemorySizeInBytesOfTsFiles() {
    return usedMemorySizeInBytesOfTsFiles;
  }
Allocate a {@link PipeMemoryBlock} for pipe only if memory used after allocation is less than
the specified threshold.

@param sizeInBytes size of memory needed to allocate
@param usedThreshold proportion of memory used, ranged from 0.0 to 1.0
@return {@code null} if the proportion of memory used after allocation exceeds {@code
    usedThreshold}. Will return a memory block otherwise.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/pipe/resource/memory/PipeMemoryManager.java