Re: [PATCH 4/10] atyfb: set FBINFO_READS_FAST

From: Mikulas Patocka
Date: Thu Jan 23 2014 - 14:31:14 EST

On Thu, 23 Jan 2014, Linus Torvalds wrote:

> Hmm. You're doing this for Matrix and now the aty driver.
> Maybe the problem is at the fbcon level? Depending on
> FBINFO_READS_FAST to decide whether you should scroll or rewrite
> sounds a bit silly: even if a device doesn't have fast reads, maybe it
> has a fast accelerated BLIT operation and scrolls quickly. Should the
> fbcon test perhaps be for FBINFO_READS_FAST _or_ the

Both mach64 and matrox have a hardware bitter that is faster than
rewriting the console - that's why FBINFO_READS_FAST improves performance
for them.

One could improve generic framebuffer core to benchmark the performance of
scrolling using blitter and rewrite and select FBINFO_READS_FAST


> I dunno. I didn't actually check the ->bcopy implementations, maybe
> they don't use copyarea. So I'm just going by a general "this feels
> wrong" feeling..
> Linus

> On Thu, Jan 23, 2014 at 10:18 AM, Mikulas Patocka <mpatocka@xxxxxxxxxx> wrote:
> > Set FBINFO_READS_FAST so that the console code uses scrolling instead of
> > rewriting. This improves scrolling speed.
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