Re: [Qemu-devel] 答复: Expansion Ratio Issue

["Alex Bennée" <alex.bennee@linaro.org>]

Chaos Shu writes:

> Hi
>
> I'm running SPEC CPU2006 on three kinds of situation, native aarch64 binary and emulator x86_64 system running SPEC CPU2006 and linux user mode level running x86_64 SPEC CPU2006 binary.
>
> To find where the performance lose, translator ? or execution of instruction after TCG? Or something else
>
> I guess most of  time, up to 90% should be spent on exec the
> instruction of TCG, does that mean the quality of translating lead to
> the performance lost directly ?

It really depends on the type of code you are executing but yes most of
the time should be spent in TCG generated code. However if you are
running a lot of FP heavy code you'll find it spends a lot of time in
helper routines calling the internal softfloat code.

I posted some patches a few months ago that enabled output to help the
Linux "perf" tool track this. I haven't got time to re-work at the
moment but it might give you a head start to instrumentation:

https://patches.linaro.org/27229/

>
> Thanks
> Chaos
>
> On 29.05.2014 13:04, Peter Maydell wrote:
>> No, we don't in general have any benchmarking of TCG codegen. I think 
>> if we did do benchmarking we'd be interested in performance 
>> benchmarking -- code expansion ratio doesn't seem like a very 
>> interesting thing to measure to me.
>
> Hi,
>
> I have a plan to play with TCG performance benchmarking. And then try to implement some optimizations. So maybe there would be some suggestions on how to perform such benchmarking? What tests seems to be appropriate for this task? I think the benchmarking should reflect real TCG use cases. So what the most typical use cases for TCG are there? Seems that system and user modes may be different from this point.
>
> Appreciate any help.
>
> Thanks,
> Sergey.

-- 
Alex Bennée