While real-time behavior and memory footprint are often important for real-time and embedded developers, ORB performance is still the most important criteria in the selection of a CORBA product. There is a prevailing mindset that the insertion of CORBA into a system consists of adding another "layer". In fact, CORBA adds minimal overhead to the system, and the amount of overhead will vary between CORBA implementations.

ORBexpress™, Objective Interface's premier object request broker (ORB), is a lightweight CORBA-compliant product optimized for use in the real-time, embedded, and high-performance development environment, combining high-speed performance with extreme reliability. For more information about ORBexpress products, please see the Products Overview page.

ORBexpress, designed from the ground up, provides developers with the smallest, fastest, most predictable ORB on the market. Inherent in the design process is our commitment to:

• Minimize the memory footprint
• Provide minimal overhead to for local and remote invocations
• Optimize the performance of the ORB within all application types

Memory Footprint
ORBexpress is designed to be flexible, offering a variety of configurations to ensure that the memory footprint is as small as possible. By using these different types of configurations, ORBexpress provides the flexibility to be used in many types of real-time, embedded, and high-performance applications.

The footprint can be configured to be as low as 93k, and any unused features will be automatically omitted from the target application. By minimizing the footprint, the internal structures are optimized within the available space, while per object overhead is very small.

Overhead
CORBA adds two types of overhead, fixed and variable, and ORBexpress is designed to minimize any overhead for local and remote operations. The graph below shows the time, in Microseconds, of a single round trip performance.

This graph identifies the minimal overhead ORBexpress provides in a two-way operation (an exercise least favorable to a CORBA system). In this instance, ORBexpress adds on 17% to the round trip time as compared to using sockets directly. Other CORBA ORBs add 200% to 1,000% overhead to the socket times. As ORBexpress scales, it will add less than 3% when sending larger volumes of data (more than 2k).

ORBexpress Performance
A number of benchmarking studies have been completed to fully document ORB performance on a variety of leading platforms, operating systems, and transports. When benchmarking ORBs, it is important to look at more than just the total time it takes for a message invocation to complete. One important measurement is the time it takes to perform the transfer without the ORB, or with TCP/IP, to measure the time a transfer takes using a simple socket program. The difference between the socket time and the time with the ORB in the loop is the true measure of the CORBA overhead.

A number of benchmarking graphs are available in the DII COE study to show the performance features of ORBexpress on a variety of operating systems and machines. Below you will find a graph comparing ORBexpress against Sockets on a single LynxOS/PPC. For additional benchmarking graphs see the DII COE study.

Latency Comparison between TCP and other Transports

The low net overhead of the ORB is necessary to support transports other than TCP/IP over ethernet. Transports can yield better speed and a lower maximum. For example when using a high performance switched fabric transport, the overhead of the TCP/IP layer becomes a significant performance barrier. As shown in the figure below, when the ORB is run out of the box using IIOP, significant time is spent in the TCP/IP stack and the round trip times are not reflective of the capabilities of the transport media. Instead, however, when a replacement transport is plugged in that makes direct use of the Switched Fabric's native APIs, the system performance show a noticeable improvement. The times of low data two way transfers now drop to ~55 microseconds.

Conclusion
ORBexpress was designed from the ground up to provide developers with the smallest, fastest, most predictable ORB on the market. The various benchmarking scenarios for:

• Memory Footprint
• Minimal Overhead
• Performance

continues to validate ORBexpress as a premier CORBA-compliant product optimized for use in the real-time, embedded, and high-performance development environment, combining high-speed performance with extreme reliability.