Could not create Data Reader

Hello jazaman,

One possibility is that this is that we are preallocating large amounts of memory for queues of your data types rather than the Monitoring data types.  The way RTI Connext DDS allocates initial queue memory is:

Maximum serialized size of your data type (assuming that all strings/sequences are at max length) x resource_limits.initial_samples

This is not usually an issue if your data types have no sequences or unions in them.  But if you have complex union, or if you have a sequence of sequences that all have a large max length, the total memory allocation can become very big.  One way to check on the maximum size of your data type is to use Monitor's Type View.  That will show you the maximum size of every data type in your system.

To open the types view, click this: 

The Types View looks like this, and the "Max Serialized" column is the maximum size of my data types:

If the maximum size of your data types is very large, the next step is to see if you can decrease the maximum sizes of sequences.   If you cannot, there are additional steps you can take.

I don't know of any reason why you would see much larger memory usage on Windows than on Linux, unless you are loading a different QoS profile.  It's also possible that you are still seeing high memory usage, but it isn't running out of memory on Linux. 

Thank you,

Rose

Hello Jamil,

These are the next steps you should take:

1. If you are not setting a maximum size of your sequences in IDL, they default to a length of 100.  Evaluate whether this is a reasonable maximum size or not.  If this is larger than you need, explicitly set the maximum sizes of your sequences: sequence<MyType, 25> mySequence;
2. Double check the DataWriters' and DataReaders' resource_limits and history QoS.  Make sure they are the same on both Windows and Linux. They would typically only be different if the wrong QoS XML file is being loaded on one platform.  (This might happen, for example, if you are starting from a different working directory on Windows than on Linux.)
3. If you are explicitly setting the maximum size of your sequences in IDL, and the typical size of your data types is much smaller than the maximum size, you can use this property to tell RTI Connext DDS to allocate a much smaller size for the data type by default.  This only exists for DataWriters, so it will help with memory usage, but helps the most if you have many DataWriters and few DataReaders. 

<datawriter_qos>
  <property>
    <value>
      <element>
        <name>dds.data_writer.history.memory_manager.fast_pool.pool_buffer_max_size</name>
        <!-- Typical size of your data type. --> 
        <value>4096</value>

      </element>  
     </value>  
   </property>  
 </datawriter_qos>   

Thank you,

Rose