Re: [Linux-fbdev-devel] RFC: Optimizing putcs()

[Geert U. <ge...@li...>]

On 6 Aug 2002, Antonino Daplas wrote:
> With fbcon-accel and the new drawing functions in linux-2.5, console
> performance degraded compared to the linux-2.4 implementation.  This is
> because putcs() has to to do 1 fb_imageblit() per character to be
> drawn.  

Yes, this will be shown badly after I'll have ported amifb to the new
framework, since chip RAM accesses are very slow and we use bitplanes...

> This can be optimized by letting putcs() initially construct the row of
> text to be drawn into an offscreen buffer, then do a single
> fb_imageblit() in the end.  Performance wil increase for several
> reasons:

Yes, this is very nice! I was thinking about passing an array of images to an
fb_imageblit_multiple() or so, but yours may be better.

> For drivers that uses cfb_imageblit or similar, a code such as the one
> below can be inserted during initialization:
> 
> info->pixmap.addr = (unsigned long) kmalloc(BUFFER_SIZE, GFP_KERNEL);
> info->pixmap.size = BUFFER_SIZE;
> info->pixmap.offset = 0;
> info->pixmap.buf_align = 1;
> info->pixmap.scan_align = 1;
> 
> Some benchmarks:
> 
> time cat /usr/src/linux/MAINTAINERS (40K text file)
> mode: 1024x768@8bpp, y-panning disabled.

  [...]

Just for reference, did you run this benchmark on 2.4.x as well?

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@li...

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds