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From Robin Garner <robin.gar...@anu.edu.au>
Subject Re: [perf] Comparative benchmarking
Date Tue, 06 Nov 2007 23:09:24 GMT
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 ?

cheers

cheers

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