Re: Reading from /dev/fb0 very slow?

[Alan Cox]

> I did some benchmarks, and my framebuffer is *way* faster when writing
> than when reading:

That is quite normal.

> 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]

Writes to a PCI device can be queued or posted. Reads from a PCI device for
obvious reasons have to stall the CPU until the data returns.