As a GC language Common Lisp is slow as molasses. However, in the realm of languages which are slow as molasses it's got quite acceptable performance. I suppose it's in part because it's alien technology from beyond the bounds of the multiverse, but also in part due to the fact that we had really interesting tech back in the '70s and '80s that kinda got lost during the so-called AI winter.

To add on to that, with declarations the programmer can tell the Lisp compiler that (for example) a variable can be stack allocated to help improve performance. The fact that Lisp code is just data is another benefit towards performance as it means macros are relatively easy to write so some computation can be done at compile time. There are also various useful utilities in the spec which can be used to help profile execution of a program to aid in optimization, such as time and trace.