0.8.12.37:

[sbcl.git] / tests / threads.impure.lisp

diff --git a/tests/threads.impure.lisp b/tests/threads.impure.lisp
index c0feefe..4881bc4 100644 (file)
--- a/tests/threads.impure.lisp
+++ b/tests/threads.impure.lisp
@@ -15,6 +15,30 @@
 
 (in-package "SB-THREAD") ; this is white-box testing, really
 
+;;; We had appalling scaling properties for a while.  Make sure they
+;;; don't reappear.
+(defun scaling-test (function &optional (nthreads 5))
+  "Execute FUNCTION with NTHREADS lurking to slow it down."
+  (let ((queue (sb-thread:make-waitqueue))
+        (mutex (sb-thread:make-mutex)))
+    ;; Start NTHREADS idle threads.
+    (dotimes (i nthreads)
+      (sb-thread:make-thread (lambda ()
+                               (sb-thread:condition-wait queue mutex)
+                              (sb-ext:quit))))
+    (let ((start-time (get-internal-run-time)))
+      (funcall function)
+      (prog1 (- (get-internal-run-time) start-time)
+       (sb-thread:condition-broadcast queue)))))
+(defun fact (n)
+  "A function that does work with the CPU."
+  (if (zerop n) 1 (* n (fact (1- n)))))
+(let ((work (lambda () (fact 15000))))
+  (let ((zero (scaling-test work 0))
+       (four (scaling-test work 4)))
+    ;; a slightly weak assertion, but good enough for starters.
+    (assert (< four (* 1.5 zero)))))
+
 ;;; For one of the interupt-thread tests, we want a foreign function
 ;;; that does not make syscalls