Re: [Qemu-devel] [v2 0/2] add avx2 instruction optimization

[Paolo Bonzini]

On 12/11/2015 10:40, Li, Liang Z wrote:
> I migrate a 8GB RAM Idle guest,  I think most of it's pages are zero pages.
> 
> I use your new code:
> -------------------------------------------------
>       unsigned long *p = ...
>       if (p[0] || p[1] || p[2] || p[3]
>           || memcmp(p+4, p, size - 4 * sizeof(unsigned long)) != 0)
>               return BUFFER_NOT_ZERO;
>       else
>               return BUFFER_ZERO;
> ---------------------------------------------------
> and the result is almost the same.  I also tried the check 8, 16 long data at 
> the beginning, 
> same result.

Interesting...  Well, all I can say is that applaud you for testing your
hypothesis with the benchmark.

Probably the setup cost of memcmp is too high, because the testing loop
is already very optimized.

Please submit the AVX2 version if it helps!

Paolo