id	summary	reporter	owner	description	type	status	priority	milestone	component	version	resolution	keywords	cc
234	[ACL2] Garbage Collection Performance on OpenMCL	ragerdl	gb	"The folks at UTexas have been playing around with mergesort, and since
you're already improving the garbage collector, you would probably like to see
this problematic example.

Can you make running the below example with garbage collection enabled as fast
as (or at least closer in performance to) executing when the garbage collector
has really large GC thresholds?  With GC effectively disabled, non-parallelized
code speeds up by a factor close to 15.  And parallelized code (via my
threading library) speeds up by a factor close to 100.

This smaller example yields a slow down of about 3 when using default garbage
collection thresholds.  This example runs on ACL2-3.3 compiled with OpenMCL
x86-64.

If you would like, I can also send you the parallelized mergesort example.
Running this would require you to download PACL2, but you've done this before,
so maybe this would be a good thing to do.

Thanks,
David



{{{
(include-book ""finite-set-theory/osets/sets"" :dir :system)

(defmacro assign$ (name value)
 `(make-event (pprogn (f-put-global
                       (quote ,name)
                       ,value
                       state)
                      (value '(value-triple nil)))))


(in-package ""SETS"")

(defun integers (n acc)
 (if (zp n)
     (reverse acc)
   (integers (1- n) (cons n acc))))

(ACL2::assign$ int-list (integers 3200000 nil))
; For true dramatic effect use this commented out version instead
; (ACL2::assign$ int-list (integers 32000000 nil))


(ACL2::cw ""Timing the serial verions of mergesort"")

(ACL2::assign$ serial-result (time$ (SETS::mergesort-exec (@ int-list))))



:q
(ccl:set-lisp-heap-gc-threshold (* 4 16777216))
(ccl:configure-egc (expt 2 16) (expt 2 17) (expt 2 17))
; For true dramatic effect use this commented out version instead
; (ccl:configure-egc (expt 2 30) (expt 2 31) (expt 2 32))


(progn

 (with-standard-io-syntax
  (let ((*package* (find-package ""CCL"")))
    (eval (read-from-string ""

 ;;; Work of Gary Byers.

 ;;; The #_ and #$ reader macros in the code below are part of
 ;;; OpenMCL's ffi; you'd basically need to hide this code in
 ;;; a file that's isolated from other implementations.
 (defun acl2::physical-memory ()
    (rlet ((info :sysinfo))
      (if (eql 0 (#_sysinfo info))
        (pref info :sysinfo.totalram))))""))))

 (defparameter *gc-min-threshold* (expt 2 31))

 (defparameter *max-mem-usage*
   (let ((phys (physical-memory)))
     (max (floor (* 6/8 phys))
          *gc-min-threshold*)))


 (defun set-and-reset-gc-thresholds ()
   (let ((n (max (- *max-mem-usage* (ccl::%usedbytes))
                 *gc-min-threshold*)))
     (cond ((not (eql n (ccl::lisp-heap-gc-threshold)))
            (ccl::set-lisp-heap-gc-threshold n)
            )))
   (ccl::use-lisp-heap-gc-threshold)
   (cond ((not (eql *gc-min-threshold*
                    (ccl::lisp-heap-gc-threshold)))
          (ccl::set-lisp-heap-gc-threshold *gc-min-threshold*)
          )))


 (defun set-max-mem-usage (max)
   (setf *max-mem-usage* max)
   (set-and-reset-gc-thresholds))

 (ccl::add-gc-hook
  #'(lambda ()
      (ccl::process-interrupt
       (slot-value ccl:*application*
                   'ccl::initial-listener-process)
       #'set-and-reset-gc-thresholds))
  :post-gc)

 (set-and-reset-gc-thresholds)

 (ccl::gc-verbose t t)
 (ccl:egc nil)
 (ccl:gc)
 )




(lp)

(ACL2::cw ""GC Disabled.  Timing the serial verions of mergesort (again)"")


(ACL2::assign$ serial-result (time$ (SETS::mergesort-exec (@ int-list))))
}}}

"	enhancement	assigned	minor		Runtime (threads, GC)			garbage collection ephemeral faster	hunt@… boyer@… gb@…