IO Contribution RatioIO Contribution RatioExternal Bus I/O Bus Transactions / External Bus Transactions (Processor-independent)
This ratio helps you to calculate the portion of all transactions on the bus were IO transactions caused by the analyzed code. A high ratio value for single-threaded code or moderate ratio value for each of the several threads running in parallel, combined with high Data Bus Utilization Ratio value, indicates that enhancement of the analyzed code may improve performance.
Parallel Computing:
If you parallelize portions of the code that require moderate bus utilization, the new total utilization can increase. Hence, gain from multithreading the program can be lower than expected. If bus utilization is high when running single-threaded program, the parallelized version can run for the same time or even longer.
If your program is multi-threaded, examining this ratio in the Thread view always gives a valid result. If you want to examine it in another view, see explanation.
If you are measuring several instances of the same single-threaded application running simultaneously, you can safely examine event counter results in the Process or Thread view. In the Module view, the results may be distorted. For further details, see explanation.