[LLVMdev] Performance vs other VMs

[Ramón García]

This is not a quite fair comparison. Other virtual machines must be
doing garbage collection, while LLVM, as it is using C code, it is
taking advantage of memory allocation by hand.

On Fri, Jan 30, 2009 at 9:56 PM, Jon Harrop <jon at ffconsultancy.com> wrote:
>
> The release of a new code generator in Mono 2.2 prompted me to benchmark the
> performance of various VMs using the SciMark2 benchmark on an 8x 2.1GHz
> 64-bit Opteron and I have published the results here:
>
>  http://flyingfrogblog.blogspot.com/2009/01/mono-22.html
>
> The LLVM results were generated using llvm-gcc 4.2.1 on the C version of
> SciMark2 with the following command-line options:
>
>  llvm-gcc -Wall -lm -O2 -funroll-loops *.c -o scimark2
>
> Mono was up to 12x slower than LLVM before and is now only 2.2x slower on
> average. Interestingly, the JVM scores slightly higher than LLVM on this
> benchmark on average and beats LLVM on two of the five individual tests.
>
> The individual scores are particularly enlightening. Specifically:
>
> . LLVM outperforms all other VMs by a significant margin on FFT, Monte Carlo
> and sparse matrix multiply.
>
> . LLVM is beaten by the JVM on successive over-relaxation (SOR) and LU
> decomposition.
>
> In the context of the SOR test, I suspect the JVM is using alias information
> to perform optimizations that LLVM and llvm-gcc probably do not do.
>
> I am not sure what causes the performance discrepancy on LU. Perhaps the JVM
> is generating SSE instructions. Does llvm-gcc generate SSE instructions under
> any circumstances?
>
> --
> Dr Jon Harrop, Flying Frog Consultancy Ltd.
> http://www.ffconsultancy.com/?e
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