Re: [Qemu-devel] Debian 7.8.0 SPARC64 on qemu - anything i can do to speedup the emulation?

[Artyom Tarasenko]

On Thu, Jul 30, 2015 at 10:55 AM, Aurelien Jarno <address@hidden> wrote:
> On 2015-07-30 10:16, Dennis Luehring wrote:
>> Am 30.07.2015 um 09:52 schrieb Aurelien Jarno:
>> >On 2015-07-30 05:52, Dennis Luehring wrote:
>> >> Am 29.07.2015 um 17:01 schrieb Aurelien Jarno:
>> >> >The point is that emulation has a cost, and it's quite difficult to
>> >> >to lower it and thus improve the emulation speed.
>> >>
>> >> so its just not strange for you to see an 1/100...200 of the native x64
>> >> speed under qemu/SPARC64
>> >> i hoped that someone will jump up an shout "its impossible - it needs to 
>> >> be
>> >> a bug" ...sadly not
>> >
>> >Overall the ratio is more around 10, but in some specific cases where
>> >the TB cache is inefficient and TB can't be linked or with an
>> >inefficient MMU, a ratio of 100 is possible.
>>
>>
>> sysbench (0.4.12) --num-threads=1 --test=cpu --cpu-max-prime=2000 run
>>    Host x64    :   1.3580s
>>    Qemu SPARC64: 184.2532s
>>
>> sysbench shows nearly ration of 200
>
> Note that when you say SPARC64 here, it's actually only the kernel, you
> are using a 32-bit userland. And that makes a difference. Here are my
> tests here:
>
> host (x86-64)                    0.8976s
> sparc32 guest (sparc64 kernel)  99.6116s
> sparc64 guest (sparc64 kernel)   4.4908s

Wow. That's quite a difference. What have you used as a sparc64 guest?
Are there any ready-to-use distributions, or have you built it from scratch?

> So it looks like the 32-bit code is not QEMU friendly. I haven't looked
> at it yet, but I guess it might be due to dynamic jumps, so that TB
> can't be chained.
>
> --
> Aurelien Jarno                          GPG: 4096R/1DDD8C9B
> address@hidden                 http://www.aurel32.net



-- 
Regards,
Artyom Tarasenko

SPARC and PPC PReP under qemu blog: http://tyom.blogspot.com/search/label/qemu