Re: [RFC] fbdev/riva:change to use generice function to implement reverse_order()

Afzal Mohammed
2015-08-24T13:42:00Z

Hi,

On Mon, Aug 24, 2015 at 04:31:13PM +0800, yalin wang wrote:
>
> i only submit the bit reverse patch for arm / arm64 arch,

yes, saw later git blaming it on you :)

> > Not for this case, but once measured on ARM, iirc, a 32-bit asm bit
> > reversal as compared to doing it in C was taking 1 cycle as opposed to
> > ~225 cycles!, of course writing optimized C could have made it fare
> > better, but still would reach no-way near asm bit reversal.

The above measurement was done not in Linux, rather on a baremetal
code, but seeing the efficient Kernel C implementation, realized that
the gain would not be that much, it would be good to know if there are
measurements for Kernel bitreversal in C & asm (on supported arch)

Regards
afzal