Hi Pavel, On Tue, Apr 7, 2015 at 2:12 PM, Pavel Machek <pa...@ucw.cz> 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 ;-) Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- ge...@linux-m68k.org 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/