Subject: Re: wsdisplay on vesafb is slow
To: Aaron J. Grier <email@example.com>
From: Michael Lorenz <firstname.lastname@example.org>
Date: 12/26/2006 03:13:05
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On Dec 26, 2006, at 01:04, Aaron J. Grier wrote:
> On Thu, Dec 21, 2006 at 04:31:24PM -0500, Thor Lancelot Simon wrote:
>> On Thu, Dec 21, 2006 at 03:58:18PM -0500, Michael Lorenz wrote:
>>> There was a proposal for a VESA BIOS extension to talk to a blitter
>>> but as far as I remember it never got anywhere.
>> Can't it use VGA text mode for text, at least?
> vesafb would cease to be a framebuffer, then, and isn't that the whole
> point of vesafb?
>> The problem is, with wscons attached to vesafb, the console is
>> unusuably slow; with wscons attached to vga, and a direct-hardware-
>> access X server, X11 is unsafe.
> so pick your poison.
On macppc we can enable caching for the framebuffer on most models
which speeds things up considerably. No idea if something similar can
be done on i386.
> has a PR been filed about the speed issue?
Do you have a fix for it? Or, do you have an idea how to fix it?
There are a few things we could do but those tend have side effects.
For instance, XFree86 uses a shadow framebuffer to avoid having to read
from video memory ( which is usually painfully slow ) - gives a nice
speed boost but costs memory, in vesafb's case kernel memory which may
or may not be acceptable. If I remember correctly Jared was at least
looking into supporting it but I'm fairly sure if it's there it's not
enabled by default.
Another thing would be to define a userland interface to switch video
modes and colour depth, then teach wsfb to use it.
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