I finally got my development XEmacs to stop core dumping, and there is visible signs of progress on the faster elisp front: Here is my generic bytecode benchmark: (progn (defun foo (a b c) (bar a b c) (bar a b c) (bar a b c)) (defun bar (d e f) nil) (byte-compile 'foo) (byte-compile 'bar) (race 200000 (foo 1 2 3))) Martin's development version: "Elapsed: 23.430829 User: 17.750000 System: 0.000000 " Function Name Ticks %/Total Call Count ===================== ===== ======= ========== bar 1164 66.174 600000 foo 518 29.449 200000 measure-compiled-form 77 4.377 1 21.2-b1: "Elapsed: 33.032012 User: 25.020000 System: 0.000000 " Function Name Ticks %/Total Call Count ===================== ===== ======= ========== bar 1586 63.874 600000 foo 799 32.179 200000 measure-compiled-form 98 3.947 1 Benchmarking harness: (when (not (fboundp 'profile-results)) (defun profile-results (&optional info stream) (get-profiling-info) (pretty-print-profiling-info))) (defmacro measure (&rest body) `(progn (let ((oct (current-time)) (opt (current-process-time))) (garbage-collect) (clear-profiling-info) (start-profiling) ,＠body (stop-profiling) (let ((ct (current-time)) (pt (current-process-time))) (print (format "Elapsed: %f User: %f System: %f\n" (+ (* 65536 (- (first ct) (first oct))) (- (second ct) (second oct)) (/ (- (third ct) (third oct)) 1000000.0)) (- (first pt) (first opt)) (- (second pt) (second opt)))))) (profile-results))) (defmacro measure-compiled (&rest body) `(progn (defun measure-compiled-form () ,＠body) (byte-compile 'measure-compiled-form) (measure (measure-compiled-form)) (disassemble 'measure-compiled-form) (fmakunbound 'measure-compiled-form))) (defmacro race (times &rest forms) `(with-output-to-temp-buffer "*Race*" ,＠(mapcar (lambda (form) `(measure-compiled (dotimes (--race-tmp ,times) ,form))) forms)))