Re: Reading from /dev/fb0 very slow?
Jeff Garzik (jgarzik@mandrakesoft.com)
Sat, 02 Jun 2001 17:42:27 -0400
Pavel Machek wrote:
>
> Hi!
>
> I did some benchmarks, and my framebuffer is *way* faster when writing
> than when reading:
>
> root@bug:/home/pavel# time cat /tmp/test > /dev/fb0
> 0.01user 0.08system 0.09 (0m0.097s) elapsed 93.13%CPU
> root@bug:/home/pavel# time cat /dev/fb0 > /dev/null
> 0.00user 0.62system 0.62 (0m0.620s) elapsed 99.93%CPU
> root@bug:/home/pavel#
>
> That is 6 times slower! This is also very visible in X, where moving
> regions is expensive, while just drawing regions is fast. For example
> gnome-terminal is *way* faster *with* transparent background option.
>
> Any idea why such assymetry? [This is toshiba 4030cdt with vesafb and
> 2.4.5]
Do you have write combining enabled?
--
Jeff Garzik | Echelon words of the day, from The Register:
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