Speed Analysis Util.

[Gustavo da Silva]

Very interesting!! Both the link and the movntq instruction. I'll read and
study.

Thanks Tobias!!

2012/12/8 Tobias Boege <tobias at gambas-buch.de>

> 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.
>
>
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-- 
Atenciosamente,

Gustavo da Silva
gustavodasilva at gmail.com
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