Re: [RFC] [PATCH] Add memcpy32 function

Bryan O'Sullivan
2005-12-28T18:11:49Z

On Wed, 2005-12-28 at 18:50 +0100, Andreas Kleen wrote:

> Ok thanks. And do you have numbers that show that the assembly
> function with rep ; movsl actually improves performance over C?

I'll see if I can ferret some numbers out. If not, I'll generate them,
but it will take me a day or so. I'm pretty sure it makes a difference
of tens to hundreds of nanoseconds, which in our case is very
significant (we measure some of our user-level performance in increments
of 10ns, very repeatably).

> If the assembly is not really faster I would recommend you just use a
> writel()
> loop in the driver instead of adding this very special purpose function
> everywhere.

Yeah, clearly if there's no difference, it's not worth the trouble.

<b