Re: [Qemu-devel] Profiling Qemu for speed?

[Christian MICHON]

I did months ago gcc/FDO with a xp/lite installation as a "repetitive task" :)
I did not improve the timings after all the effort.

Christian

On 4/18/05, Daniel Egger <address@hidden> wrote:
> On 18.04.2005, at 11:51, Ian Rogers wrote:
> 
> > I'm not sure if you can get GCC to generate code sequences like this,
> > but you probably at least need to use the -fprofile-generate and
> > -fprofile-use options
> > http://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html
> 
> Feedback optimisation (FDO) will not work for two reasons:
> a) qemu itself is something like a realtime compiler so FDO
>     will only speed up the compiler but not the generated code
> b) FDO will only provide speed boosts if the feedback phase
>     has a chance to analyse a representative work pattern that
>     is hopefully also repetitive
> 
> After all FDO is mostly about making a tradeoff size/speed
> and rearranging code (mostly branches) to avoid branch
> mispredictions of the CPU.
> 
> Servus,
>        Daniel
> 
> 
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> 


-- 
Christian