Here are ways of improving the execution speed of byte-compiled
Profile your program with the elp library. See the file
elp.el for instructions.
Check the speed of individual Emacs Lisp forms using the
benchmark library. See the functions benchmark-run and
benchmark-run-compiled in benchmark.el.
Use iteration rather than recursion whenever possible.
Function calls are slow in Emacs Lisp even when a compiled function
is calling another compiled function.
Using the primitive list-searching functions memq, member,
assq, or assoc is even faster than explicit iteration. It
can be worth rearranging a data structure so that one of these primitive
search functions can be used.
Certain built-in functions are handled specially in byte-compiled code,
avoiding the need for an ordinary function call. It is a good idea to
use these functions rather than alternatives. To see whether a function
is handled specially by the compiler, examine its byte-compile
property. If the property is non-nil, then the function is
For example, the following input will show you that aref is
compiled specially (see Array Functions):
(get 'aref 'byte-compile)
If calling a small function accounts for a substantial part of your
program's running time, make the function inline. This eliminates
the function call overhead. Since making a function inline reduces
the flexibility of changing the program, don't do it unless it gives
a noticeable speedup in something slow enough that users care about
the speed. See Inline Functions.