You can find out the performance impact by adding the
timing on
statement at the beginning of the iRule. That'll generate timing stats for each event.
If you want finer grained you can use the [clock ] command to get the timings at high resolution and work out the performance by logging the clock at various points (Via HSL. Although of course adding these commands will affect the timings against the iRule without them). 🙂
There have been a few discussions here on devcentral over the last few years about what's more efficient. And IIRC there were some real examples as well.
H