Bug#755739: VGA-mode newcons very slow

[Ed Maste <emaste@freebsd.org>]

On 20 August 2014 15:56, Steven Chamberlain <steven@pyro.eu.org> wrote:
> Hi,
>
> I've tested for this vt(4) issue in upstream's own kernel build from:
> ftp://ftp.freebsd.org/pub/FreeBSD/snapshots/amd64/10.0-STABLE
> and it is affected as well.  It is only a problem when using Qemu with
> the "-enable-kvm" option (and some virtualisation platforms will do this) :

There is a patch in discussion to fix the vt_vga performance issue
that you could try out if you like.

The thread is here:
http://lists.freebsd.org/pipermail/freebsd-current/2014-August/051731.html
The current version of the patch:
https://people.freebsd.org/~dumbbell/vt/vt-vga.5.patch

We plan to get a version of this into 10.1-RELEASE.



>
> On 08/08/14 01:52, Steven Chamberlain wrote:
>> With hw.vga.textmode=1, it takes about a second for the first kernel
>> messages to fill the screen;  the only apparent delay here would be the
>> kernel doing things between printing each line of output.
>>
>> With hw.vga.textmode=0, the same takes about 6 seconds, with noticeable
>> delay between printing each character (like a really slow serial tty)
>> and even slower once the screen is filled and starts to scroll.
>
> I could file a FreeBSD PR about this 'soon', but can't right now, sorry.
>
> Thanks,
> Regards,
> --
> Steven Chamberlain
> steven@pyro.eu.org