diff --git a/collects/tests/mzscheme/benchmarks/mz/redsem.scm b/collects/tests/mzscheme/benchmarks/mz/redsem.scm
index a233311e1d..fe7c068576 100644
--- a/collects/tests/mzscheme/benchmarks/mz/redsem.scm
+++ b/collects/tests/mzscheme/benchmarks/mz/redsem.scm
@@ -1,7 +1,20 @@
-(require (planet "beginner.ss" ("robby" "redex.plt") "examples"))
+#|
+
+Time the cache-less version of the pattern matcher
+under the theory that if this speeds up, the cache
+can be used less, leading to less memory use, and
+better performance.
+
+(and I'm pretty sure that measuing the cache isn't
+super useful.)
+
+Robby
+
+|#
+
+(require (planet "reduction-semantics.ss" ("robby" "redex.plt" 2 4)))
+(set-cache-size! #f)
+(require (planet "beginner.ss" ("robby" "redex.plt" 2 4) "examples"))
 (collect-garbage)
 (printf "Now\n")
-(time (begin 
-	(run-tests) (run-tests) (run-tests) (run-tests) (run-tests)
-	(run-tests) (run-tests) (run-tests) (run-tests) (run-tests)
-	))
+(time (begin (run-tests) (run-tests) (run-tests)))