4. Vortex OpenSplice Architectural Modes — OpenSplice Evaluation and Benchmarking Guide

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# 4. Vortex OpenSplice Architectural Modes

Vortex OpenSplice provides two main architectural modes. These are the Single Process deployment mode, which provides a Standalone architecture, and, unique to OpenSplice, the Shared Memory deployment mode which provides a Federated architecture.

## 4.1. The Single Process or Standalone deployment

Features of this mode are:

- Simplest to run and get started with.
- Each DDS application process contains the entire DDS infrastructure.
- Uses in-process heap memory for the DDS database.
- Vortex OpenSplice services run as threads within the application process.
- When there are multiple DDS application processes on a single machine, the communication between them must be done via a networking service; this introduces additional overhead so performance in this scenario is not optimal.

Single Process or Standalone deployment

## 4.2. The Shared Memory or Federated deployment

Features of this mode are:

- The DDS infrastructure is started once per machine.
- Uses shared memory for the DDS database.
- Each DDS application process interfaces with the shared memory rather than creating the DDS infrastructure itself.
- Allows the data to be physically present only once on any machine.
- Reading and writing directly to locally-mapped memory is far more efficient than having to actually move the data via a networking service, allowing for improved performance and scalability.
- Vortex OpenSplice services are able to arbitrate over all of the DDS data on the node, and so can make smart decisions with respect to data delivery so that priority QoS values (for example) are respected; this is not possible when there are multiple standalone deployments on a machine.

Shared Memory or Federated deployment

When there are multiple DDS applications running on a single computing node, the use of OpenSplice’s unique Shared Memory architecture can provide greater performance, smaller footprint and better scalability than other DDS deployment options.

## 4.3. How to select the Architectural Mode

- For a Single Process deployment, set the OSPL_URI variable to refer to a single process (sp) xml file such as `ospl_sp_ddsi.xml` or `ospl_sp_nativeRT.xml`. Note that a networking service (such as ddsi or nativeRT) is required for two DDS application processes to communicate even if they are running on the same physical machine. See the next section for more details on networking options.

A single process deployment is enabled when the Domain section of the XML configuration contains a ‘<SingleProcess> TRUE’ attribute.

NOTE for VxWorks kernel mode builds of OpenSplice the single process feature of the OpenSplice domain must not be enabled. i.e. “<SingleProcess>true</SingleProcess>” must not be included in the OpenSplice Configuration xml. The model used on VxWorks kernel builds is always that an area of kernel memory is allocated to store the domain database ( the size of which is controlled by the size option in the Database configuration for opensplice as is used on other platforms for the shared memory model. ) This can then be accessed by any task on the same VxWorks node.

- For a Shared Memory deployment, set the `OSPL_URI` variable to refer to a shared memory (shmem) xml file such as `ospl_shmem_no_network.xml`, `ospl_shmem_ddsi.xml`, or `ospl_shmem_nativeRT.xml`. Note that two or more DDS applications running on the same physical machine are able to communicate via the shared memory so a networking service (such as ddsi or nativeRT) is not necessarily required.

A shared memory deployment is enabled when the Domain section of the XML configuration does not contain a ‘<SingleProcess> TRUE’ attribute but does contain a ‘<Database>’ attribute.

Note that by default the `OSPL_URI` environment variable refers to a Single Process configuration, so to see the extra performance and scalability benefits of Vortex OpenSplice’s Shared Memory architecture it is necessary to switch from the default.

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