linux-kernel - Re: [PATCH v2 0/4] have the vt console preserve unicode characters

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Message-ID: <nycvar.YSQ.7.76.1806221222340.16670@knanqh.ubzr>
Date:   Fri, 22 Jun 2018 12:28:17 -0400 (EDT)
From:   Nicolas Pitre <nicolas.pitre@...aro.org>
To:     Alan Cox <gnomes@...rguk.ukuu.org.uk>
cc:     Adam Borowski <kilobyte@...band.pl>, Dave Mielke <Dave@...lke.cc>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Samuel Thibault <samuel.thibault@...-lyon.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/4] have the vt console preserve unicode characters

On Fri, 22 Jun 2018, Alan Cox wrote:

> > The other point is a quite pointless assumption that existing scrollback is
> > "optimized".  Even vgacon mostly uses software scrollback these days, as the
> > amount of VGA display memory is really small.
> 
> All of our console driver code is horribly unoptimized for most of
> todays hardware. Long ago I did look at what was needed but it's a
> seriously non-trivial change. In particular
> 
> - Console I/O occurs under enough locks to keep fort knox safe. That
>   means it's very very hard to accelerate
> 
> - The logic is plain wrong for a lot of modern video. We shouldn't be
>   scrolling, we should be rendering the current backing text buffer at
>   video refresh rate or similar and if the source of the updates outruns
>   us it doesn't matter - we don't have to draw all the glyphs as if we
>   were fast enough they would have been a blur anyway.

My executive summary from what you say is that there is no longer an 
advantage to maintain a central vga-style glyph buffer in the core 
console code, right?


Nicolas