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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Thu, 20 Jan 2022 10:06:01 +0100
Message-ID: <CAMuHMdWV+-+Jr7HggbfH_GEDcdep4pJLiMG+15jxBvQ91BCS0w@mail.gmail.com>
Subject: Re: [PATCH] MAINTAINERS: Add Helge as fbdev maintainer
To:     Gerd Hoffmann <kraxel@redhat.com>
Cc:     Pekka Paalanen <ppaalanen@gmail.com>,
        Sven Schnelle <svens@stackframe.org>,
        DRI Development <dri-devel@lists.freedesktop.org>,
        Helge Deller <deller@gmx.de>,
        Linux Fbdev development list <linux-fbdev@vger.kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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Hi Gerd,

On Thu, Jan 20, 2022 at 4:29 AM Gerd Hoffmann <kraxel@redhat.com> wrote:
> On Tue, Jan 18, 2022 at 10:33:23AM +0200, Pekka Paalanen wrote:
> > On Mon, 17 Jan 2022 19:47:39 +0100
> > Sven Schnelle <svens@stackframe.org> wrote:
> >
> > > I also tested the speed on my Thinkpad X1 with Intel graphics, and there
> > > a dmesg with 919 lines one the text console took about 2s to display. In
> > > x11, i measure 22ms. This might be unfair because encoding might be
> > > different, but i cannot confirm the 'memcpy' is faster than hardware
> > > blitting' point. I think if that would be the case, no-one would care
> > > about 2D acceleration.
> >
> > I think that is an extremely unfair comparison, because a graphical
> > terminal app is not going to render every line of text streamed to it.
> > It probably renders only the final view alone if you simply run
> > 'dmesg', skipping the first 800-900 lines completely.
>
> Probably more like "render on every vblank", but yes, unlike fbcon it
> surely wouldn't render every single character sent to the terminal.
>
> Also acceleration on modern hardware is more like "compose window
> content using the 3d engine" than "use 2d blitter to scroll the window".
>
> > Maybe fbcon should do the same when presented with a flood of text,
> > but I don't know how or why it works like it works.
>
> fbcon could do the same, i.e. render to fbdev in a 60Hz timer instead of
> doing it synchronously.

Hopefully only the parts of the screen which need a redraw?

Not all displays can be updated that fast. For a "modern" example, see
https://patchwork.freedesktop.org/series/93070/.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@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