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

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.

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

Sam

>
> ----------------------------------------
>
> #lang racket/base
> (require ffi/unsafe)
>
> (define N 1000)
>
> (define p (malloc N))
>
> (time
>  (for ([i (in-range 1000)])
>    (for ([j (in-range N)])
>      (ptr-set! p _byte j 42))))
>