presto-main/src/main/java/io/prestosql/connector/informationschema/InformationSchemaPageSource.java/InformationSchemaPageSource/getSystemMemoryUsage
class InformationSchemaPageSource:    @Override
    public long getSystemMemoryUsage()
    {
        return memoryUsageBytes + pageBuilder.getRetainedSizeInBytes();
    }