[racket-dev] [plt] Push #28239: master branch updated

At Tue, 25 Feb 2014 09:37:27 -0500, Sam Tobin-Hochstadt wrote:
> On Tue, Feb 25, 2014 at 9:32 AM, Matthew Flatt <mflatt at cs.utah.edu> wrote:
> > At Tue, 25 Feb 2014 09:22:54 -0500, Sam Tobin-Hochstadt wrote:
> >> On Tue, Feb 25, 2014 at 8:34 AM,  <mflatt at racket-lang.org> wrote:
> >> >
> >> > eff53cd Matthew Flatt <mflatt at racket-lang.org> 2014-02-24 16:42
> >> > :
> >> > | treat FFI primitives like other primitives internally
> >> > |
> >> > | This change paves the way for JIT-inlining FFI operations
> >> > | such as `ptr-ref`. Even without JIT treatment, the change
> >> > | slightly reduces the overhead for calling FFI primitives.
> >>
> >> Do you have benchmarks for the FFI that you used here?
> >
> > The claim of reduced overhead was based on removing indirections
> > through scheme_do_eval(), as visible in a low-level profile of a
> > drawing loop.
> >
> > Now that you ask, though, the change cuts about 25% of the time for the
> > loop below on my machine.
> 
> Nice!
> 
> What code in the drawing loop were you profiling, though? I'm really
> looking for a larger-scale Racket program where the FFI is
> performance-important, rather than a micro-benchmark.

See below, but I don't think FFI performance turns out to be crucial.
Streamlining calls of FFI functions was more about reducing noise in
the information that I was looking at (i.e., making sure I understood
where scheme_do_eval() indirections came from).

I have been looking at editor refresh in DrRacket, and while time spent
in foreign functions is significant, it doesn't appear that the path to
get there is a bottleneck.

> Would the slideshow benchmark from our OOPSLA paper be a reasonable choice 
> here?

No, that benchmark mostly constructs picts without rendering them.

Offhand, I can't think of an existing program that makes a good
benchmark, but I'll keep it in mind.

----------------------------------------

#lang racket/gui

(define bm (make-bitmap 600 600))
(define dc (send bm make-dc))

(define (copy n s) (apply string-append (for/list ([i (in-range n)]) s)))

(define (go)
 (for ([i (in-range 100)])
   (for ([j (in-range 100)])
     (send dc draw-text "hello" (* i 5) (* j 5)))))

(time (go))
(time (for ([i (in-range 50)])
        (go)))