Appendix A. Performance Impact; Overhead Of Performance Measurement Techniques; Rta Effects On Cpu Load - Texas Instruments DSP/BIOS Real-Time Analysis (RTA User Manual

Dsp/bios real-time analysis (rta) and debugging applied to a video application

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A.1 Overhead of Performance Measurement Techniques

Because most of the benchmarking APIs are called once every 30 frames, the additional CPU

load expected after adding the instrumentation is low. The measured performance of the

benchmarking techniques is given in Table 3. A spreadsheet containing the expected and actual

timing values is provided with the software distribution.

Table 3.

Benchmark

MBX check in process Task

LOAD module call

Single Call to UTL_stsStart

Single Call to UTL_stsStop

Capture Task benchmarking

Display Task benchmarking

Process Task benchmarking

Control Task

SubTotal Load (Task bchmrk)

SubTotal Load (UTL calls)

Total Load of benchmarking

These benchmarks are given in instructions, and the individual CPU load of each function is

calculated by dividing the benchmark by 20M instructions per frame, the number of cycles

available on a 600 MHz 64x device in a 30 fps NTSC system.

These benchmarks were measured using UTL_stsStart and UTL_stsStop API calls bracketing

the regions of code to be benchmarked. For example, to benchmark the LOAD_getcpuload

function, the measurement code was the following:

UTL_stsStart( stsBenchmark1 );

benchVid.cpuLoad.current = LOAD_getcpuload();

UTL_stsStop( stsBenchmark1 );

This method of benchmarking allows execution time to be measured in real-time, although if an

interrupt or context switch occurs between the UTL calls, the time spent executing the interrupt

or out-of-context code would also be included in the benchmark.

A.2 RTA Effects on CPU Load

The CPU load was measured with RTA debugging turned off and the UTL_DBGLEVEL set to

40. The total CPU load of the application with the instrumentation turned off was 93% average

and 95% peak. The CPU load of the instrumented application was 93% average and 95% peak

when using the same video content, a repeating high-motion sequence from a DVD. The

benchmarking did not make a statistically significant impact on the CPU load.