> Note that due to things like cache line misses, looking at the code will
> tell you almost nothing about which is *really* the "best" code...

I thought of counting number of instructions in disassembled code for each case. Since I'm only replacing certain API's , rest of the code remains same.

For example

Replacing ACCESS_ONCE() API with READ_ONCE()

Please correct me , if I'm wrong.

> Why do you need to cross-compile? Just build the drivers as x86_64. Pretty
> much anybody who actually *cares* about performance has moved off 32-bit
> kernels a while ago (unless you're stuck with an embedded 32-bit CPU).

Earlier, whenever I run this command

$ make drivers/staging/rdma/

I was getting this error

CONFIG_X86_X32 enabled but no binutils support

So, I thought to cross compile for x82. But now it seems i have solved by following this

On Tue, Jun 7, 2016 at 3:16 AM, <Valdis.Kletnieks@vt.edu> wrote:

On Tue, 07 Jun 2016 02:27:03 +0530, Shyam Saini said:

> To choose best optimized code, i need to first compile them and then
> disassemble the compiled code, where a change in single line would make a
> significant difference in the performance.

Note that due to things like cache line misses, looking at the code will
tell you almost nothing about which is *really* the "best" code...

> So, my question is how to compile* x86 based network drivers on x86_64
> Ubuntu machine*. Currently I'm running Ubuntu 14.04.

Why do you need to cross-compile? Just build the drivers as x86_64. Pretty
much anybody who actually *cares* about performance has moved off 32-bit
kernels a while ago (unless you're stuck with an embedded 32-bit CPU).