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
<http://stackoverflow.com/questions/12501124/errors-in-compiling-linux-kernel-module-config-x86-x32-enabled-but-no-binutils>

On Tue, Jun 7, 2016 at 3:16 AM, [off-list ref] wrote:

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

quoted

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

quoted

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...

quoted

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).

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