from the help file at:
A single background process can consume 100% of a single CPU core, and sometimes even more for certain tasks. As a result of this, the total number of instances you should run depends on the machine’s available cores—as well as on what you’re trying to improve. The deployment examples below uses
Nto represent the machine’s total number of cores, and each suggests a different strategy where the background process is concerned. When in doubt, start with the low end of the suggested range and assess performance before increasing the number.
How many cores on the machine running backgrounder processes? Is this machine running other Tableau Server processes (vizql, application, etc.)? The recommendation is dependent on the number of cores, and the reality is if your backgrounder tasks do not cause performance degradation in other parts of Tableau Server, you are probably fine to up the number of processes to complete the tasks quicker. This is very much "your mileage may vary", so I would test and monitor different configurations and keep in mind there is a trade-off between resources for backgrounder and other processes on the same box.