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From
SubjectRe: scrollback
Date
Followup to:  <3272A0FE.52193236@uiuc.edu>
By author: Keith Rohrer <kwrohrer@uiuc.edu>
In newsgroup: linux.dev.kernel
>
> Try switching between a "normal" VC and a VC in graphics mode (e.g. X)
> and back sometime. That overhead is (1) copying the necessary amount of
> video RAM (2-4 megs total) to + from virtual main memory (with
> associated pages getting written out to the swap space), and (2)
> possibly paging in code to write to the backing store rather than to the
> screen. It's not too bad for a full graphics screen if you don't need
> to swap it in, and the tails of the little scrollback buffers would fit
> in the cache much more easily than a meg or two of X screen...
>
> It's not as bad as you think.
>

It's not bad at all, having written programs that do exactly that. It
is only that currently, kernel memory is not swappable. I am
suspecting it is getting unavoidable to add swappable kernel memory;
there are indeed a number of features (like tmpfs) that cannot be
reasonably done without it.

As far as the console, though, there is an alternative: consoled.
There are simply features that do not belong in kernel space (dynamic
font generation comes to mind.) However, it is perfectly reasonable to
do a console manager in user space, using "graphics"
(i.e. software-managed) console mode and raw keyboard mode; and, of
course, PTY's.

-hpa
--
Not speaking for Transmeta in any shape, way, or form.

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