Very interesting!! Both the link and the movntq instruction. I'll read and study. Thanks Tobias!! 2012/12/8 Tobias Boege <tobias@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@gmail.com