A parameter where? Obviously not in the code of the function itself; polluting your application code with flags such as log=true|false is obviously a no-go. Especially since logging is only one such "cross cutting concern", one of many, and you simply cannot go polluting your code with all of them because it leads to a mess.

Many Java logging systems allow you to enable/disable logging per package, but this is still not enough for a per function decision.

Logging is a hard problem.