Speed Analysis Util.

[tobias@gambas-buch.de (Tobias Boege)]

On Sat, 08 Dec 2012, Gustavo da Silva wrote:
> Hello Kernel Brothers!! How are you???
> 
> So, I would like test the performance of my notebook, developing one or two
> utilities, and have a better
> mensurement about the speed.
> 
> But it can help all of us.
> 
> 1st: I would like mensure the speed making a counter (exacly bogomips? may
> be). Loop+counter during 1 tickrate.
> 2nd: The most interesting: How many memory cells in ram can we
> access during 1tickrate? How could we develop this?!
> 
> Both utils may run in long mode (64bits). Well, in real mode too; so, we
> can compare the speed in the two modes!
> 
> Some one knows how to develop a very small program/routine about that?!
> 
> For the 2nd situation, a simple idea wrote in codesnipet form (consider the
> intention, not the sintax! there are bugs! I know. Intel syntax.)

Obviously! ;-)

> 
>   dw the_counter_cell 0
>   lea bx, the_counter_cell
>   xor bx,bx
> label:
>   inc [bx]    # Could not be so simple like this, because the address can
> be cached. Right?
>   loop label # breaked by an interruption. Just to express the intention.
> 
> How could we create a small code for the 2nd situation, tring to force the
> processor to not use the cache?

As Drepper says[0], use the movntq instruction on x86_64 to bypass the
cache.

Regards,
Tobi

[0] http://www.akkadia.org/drepper/cpumemory.pdf p. 47ff.