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

[Alex Bennée]

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