Re: [PATCH v6 1/3] target/ppc: Optimize emulation of vpkpx instruction

[Stefan Brankovic <stefan.brankovic@rt-rk.com>]

On 29.8.19. 17:31, Richard Henderson wrote:
> On 8/29/19 6:34 AM, Stefan Brankovic wrote:
>> Then I run my performance tests and I got following results(test is calling
>> vpkpx 100000 times):
>>
>> 1) Current helper implementation: ~ 157 ms
>>
>> 2) helper implementation you suggested: ~94 ms
>>
>> 3) tcg implementation: ~75 ms
> I assume you tested in a loop.  If you have just the one expansion, you'll not
> see the penalty for the icache expansion.  To show the other extreme, you'd
> want to test as separate sequential invocations.
Yes, testing is done in a loop.
>
> That said, I'd be more interested in a real test case that isn't just calling
> one instruction over and over.  Is there a real test case that shows vpkpx in
> the top 25 of the profile?  With more than 0.5% of runtime?
>
>
> r~

I made an experiment where I started MAC OSX 10.4 in QEMU system mode 
and I found out that vpkpx instruction is widely used to display 
different graphical elements. With that in mind, this performance 
improvement is of great importance.

Also, vpkpx instruction is often used in a loop, to process big amount 
of pixels at once. That's why testing performance of this instruction in 
a loop should give good insight of how this instruction perform overall.

Kind Regards,

Stefan