Aries Performance
Perhaps the largest issue surrounding the execution of non-native code is performance. In some cases, the execution of non-native code can lead to unacceptable performance degradation. Performance under Aries depends on application characteristics.
HP has performed benchmarks comparing the performance of applications running native on PA-RISC to that of the same applications running under Aries on Itanium-based systems of comparable performance. The objective was to determine the amount of performance degradation that occurred when the application was moved from PA-RISC to Itanium and executed using the Aries dynamic code translation technology.
The results have shown that general commercial applications spending significant time utilizing operating system services and/or performing a large amount of I/O (with mass storage and/or in interaction with users) suffer very little or no performance degradation when using Aries compared to the performance of a similar class PA-RISC system. These applications can be classified as system-intensive applications.
Aries has been optimized to deliver the best performance for commercial applications with the characteristics listed above. Performance for applications that are compute-intensive is more degraded (and applications that are floating-point computation-intensive will see significant performance degradation). Examples of these are technical and analytical workloads or commercial workloads utilizing databases. For these types of applications, recompilation using a native mode compiler is recommended. With very few exceptions, PA-RISC applications can be recompiled for native Itanium mode without modifying source code. For example, 32-bit PA-RISC applications do not need to be converted into 64-bit applications in order to successfully compile on Itanium.
It is also possible to have some executables of an application run under Aries and have other executables run in native mode. A comparison of performance under either architecture is displayed in Figure 12-3.
Figure 12-3. Performance of applications under Aries
System-intensive and nonperformance-sensitive applications can run under Aries while performance-sensitive applications can be recompiled for native execution in order to get maximum performance.
Note: Executables on Itanium must be all PA-RISC or all Itanium; mixed-mode executables are not allowed.