On Tue 2015-04-07 14:19:33, Geert Uytterhoeven wrote:
> Hi Pavel,
>
> On Tue, Apr 7, 2015 at 2:12 PM, Pavel Machek <[email protected]> wrote:
> > I have an socfpga board, which uses has simple framebuffer implemented
> > in the FPGA. On 3.15, framebuffer is fast:
> >
> > root@wagabuibui:~# time cat /dev/fb0 > /dev/null
> > real 0m 0.00s
> > user 0m 0.00s
> > sys 0m 0.00s
> >
> > on 3.18, this takes 220msec. Similar slowdown exists for
> > writes. Simple framebuffer did not change at all between 3.15 and
> > 3.18; resource flags of the framebuffer are still same (0x200).
> >
> > If I enable caching on 3.18, it speeds up a bit, to 70msec or
> > so... Which means problem is not only in caching.
> >
> > Any ideas?
>
> My first guess was commit 67dc0d4758e5 ("vt_buffer: drop console buffer
> copying optimisations"), but this was introduced only in v4.0-rc1.
>
> Just in case you encounter another performance regression after upgrading
> to a more modern kernel ;-)
:-). I did a git bisect, and it pointed to this. And reverting it
indeed fixes the problem in 3.18. Problem is still there in 4.0.
Archit do you know what is going on there? Should the revert be filled
for 4.0?
Pavel
commit 981409b25e2a99409b26daa67293ca1cfd5ea0a0
Author: Archit Taneja <[email protected]>
Date: Fri Nov 16 14:46:04 2012 +0530
fbdev: arm has __raw I/O accessors, use them in fb.h
This removes the sparse warnings on arm platforms:
warning: cast removes address space of expression
Signed-off-by: Archit Taneja <[email protected]>
Signed-off-by: Tomi Valkeinen <[email protected]>
Cc: H Hartley Sweeten <hsweeten at visionengravers.com>
Cc: Alexander Shiyan <[email protected]>
Cc: Russell King <[email protected]>
> Gr{oetje,eeting}s,
>
> Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 --
> [email protected]
>
> 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
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures)
http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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