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From "Xiao-Feng Li" <xiaofeng...@gmail.com>
Subject Re: [perf] Comparative benchmarking
Date Wed, 07 Nov 2007 02:46:20 GMT
On Nov 7, 2007 7:09 AM, Robin Garner <robin.garner@anu.edu.au> wrote:
>
> Aleksey Shipilev wrote:
> > On 07 Nov 2007 00:27:25 +0300, Egor Pasko <egor.pasko@gmail.com> wrote:
> >
> >> Vladimir, guess what? :) I actually mixed several things
> >> altogether.
> >>
> > <giggly>(sigh) As usual, miracle does not happen :) I dreamed to see
> > software sqrt() implementation that could be faster than hardware one.
> > </giggly>
> >
> >
> >> So, we are left with SSE asm that can be inlined by JIT and AFAI can
> >> see it is not as fast as HotSpot? Weird :)
> >>
> > No, for now we have just the intrinsic in native code, so we also have
> > overheads for JNI transition (and it is heavy!), parameter passing,
> > chains of calls, etc. I believe that sqrt() magic will lead that NBody
> > performance very close to RI.
> >
> > BTW, in my thought this benchmark is like the top of the iceberg
> > called "FP performance problems".
> >
> > Thanks,
> > Aleksey.
> >
> You might be interested to know that the JikesRVM implementation calls
> out to glibc via a fast syscall (we have an @SysCall annotation for
> native methods), and it is 1.5x slower than Sun 1.6 on a Core2/Linux for
> Tim's (non-strict) benchmark.  Maybe you can squeeze the overhead of
> intrinsic calls down a bit further ?

I am also wondering why not to leverage the system support directly.
This solution is by default portable. :-)

> cheers
>
> cheers
>



-- 
http://xiao-feng.blogspot.com

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