poor scrolling in qemu-kvm

poor scrolling in qemu-kvm

[Federico Beffa]

Hi,

I'm experimenting with the system in a qemu-kvm virtual machine. I
created an image and successfully booted. However, scrolling of the
display is unusably slow (e.g. displaying dmesg). The same problem is
also visible in Ludovic's presentation

http://audio-video.gnu.org/video/ghm2014/2014-08--courtes--were-building-the-gnu-system--ghm.webm

at about min. 41.

For comparison I run an ubuntu live cd (in text mode) and it performs very well.

Have someone found out the reason for this poor performance in
qemu-kvm and how to fix it?

Thanks,
Fede

Re: poor scrolling in qemu-kvm

[Federico Beffa]

On Sat, Nov 29, 2014 at 5:23 PM, Federico Beffa <beffa@ieee.org> wrote:
> Hi,
>
> I'm experimenting with the system in a qemu-kvm virtual machine. I
> created an image and successfully booted. However, scrolling of the
> display is unusably slow (e.g. displaying dmesg). The same problem is
> also visible in Ludovic's presentation
>
> http://audio-video.gnu.org/video/ghm2014/2014-08--courtes--were-building-the-gnu-system--ghm.webm
>
> at about min. 41.
>
> For comparison I run an ubuntu live cd (in text mode) and it performs very well.
>
> Have someone found out the reason for this poor performance in
> qemu-kvm and how to fix it?
>

Interestingly, under X the system performs pretty well. So, its a text
mode problem.

Fede

Re: poor scrolling in qemu-kvm

[Ludovic Courtès]

Federico Beffa <beffa@ieee.org> skribis:

> Have someone found out the reason for this poor performance in
> qemu-kvm and how to fix it?

Yes, I eventually found out: by default, QEMU uses a Cirrus VGA graphics
adapter emulator, which is damn slow for this kind of framebuffer thing.

The right thing is to use ‘-vga std’, which uses a “standard VGA”
emulator, which doesn’t have this problem.

However, X will fail to start currently when using this.  The fix is to
use xf86-video-modesetting.  But this driver is not currently usable
because it requires a version of libdrm incompatible with that currently
used by xorg-server/MESA.

Long story short: we just need to update MESA to use the newer libdrm,
and we should be able to fix that.

Would you like to try?  :-)

Thanks,
Ludo’.

Re: poor scrolling in qemu-kvm

[Andreas Enge]

On Sat, Nov 29, 2014 at 09:53:54PM +0100, Ludovic Courtès wrote:
> Long story short: we just need to update MESA to use the newer libdrm,
> and we should be able to fix that.
> Would you like to try?  :-)

I did try to update mesa, which was the source of some new packages in the
xorg module. However, if I remember correctly, a newer mesa would essentially
force us to upgrade all of our X. And so far, the policy has been to stay with
the releases stable R7.7. Just as a warning that by upgrading something, you
may be in for upgrading a lot, which we might not wish to do.

Andreas

Re: poor scrolling in qemu-kvm

[Ludovic Courtès]

Andreas Enge <andreas@enge.fr> skribis:

> On Sat, Nov 29, 2014 at 09:53:54PM +0100, Ludovic Courtès wrote:
>> Long story short: we just need to update MESA to use the newer libdrm,
>> and we should be able to fix that.
>> Would you like to try?  :-)
>
> I did try to update mesa, which was the source of some new packages in the
> xorg module. However, if I remember correctly, a newer mesa would essentially
> force us to upgrade all of our X. And so far, the policy has been to stay with
> the releases stable R7.7. Just as a warning that by upgrading something, you
> may be in for upgrading a lot, which we might not wish to do.

Oh, right.

OTOH the real R7.7 is getting old, no?  Should we really wait for the
next big joint release?

Thanks,
Ludo’.

Re: poor scrolling in qemu-kvm

[Federico Beffa]

On Sat, Nov 29, 2014 at 10:20 PM, Andreas Enge <andreas@enge.fr> wrote:
> On Sat, Nov 29, 2014 at 09:53:54PM +0100, Ludovic Courtès wrote:
>> Long story short: we just need to update MESA to use the newer libdrm,
>> and we should be able to fix that.
>> Would you like to try?  :-)

I will first finish the work on numpy/scipy .I will then give it a go.

>
> I did try to update mesa, which was the source of some new packages in the
> xorg module. However, if I remember correctly, a newer mesa would essentially
> force us to upgrade all of our X. And so far, the policy has been to stay with
> the releases stable R7.7. Just as a warning that by upgrading something, you
> may be in for upgrading a lot, which we might not wish to do.
>

Right now there are newer versions than the ones mentioned in the
comment of the mesa package.  If things require substantial upgrades I
will get back to the list.

Regards,
Fede

Re: poor scrolling in qemu-kvm

[Andreas Enge]

On Sun, Nov 30, 2014 at 05:05:30PM +0100, Federico Beffa wrote:
> Right now there are newer versions than the ones mentioned in the
> comment of the mesa package.  If things require substantial upgrades I
> will get back to the list.

I know, but I tried to package mesa 10 until I realised it would mean more
massive upgrades.

Now, I am not necessarily opposed to switching to newer x.org packages
everywhere. But in this case, it would be nice to start with a "guxi refresh"
that works more generally, and at least on the packages mirrored on x.org.

Andreas

Re: poor scrolling in qemu-kvm

[Federico Beffa]

On Sun, Nov 30, 2014 at 6:47 PM, Andreas Enge <andreas@enge.fr> wrote:
> On Sun, Nov 30, 2014 at 05:05:30PM +0100, Federico Beffa wrote:
>> Right now there are newer versions than the ones mentioned in the
>> comment of the mesa package.  If things require substantial upgrades I
>> will get back to the list.
>
> I know, but I tried to package mesa 10 until I realised it would mean more
> massive upgrades.
>
> Now, I am not necessarily opposed to switching to newer x.org packages
> everywhere. But in this case, it would be nice to start with a "guxi refresh"
> that works more generally, and at least on the packages mirrored on x.org.
>

Hi Andreas,

It sounds like you did quite some work on it already.  Please go on if
you like. I'm not trying to step on anyone's feet :-)

Regards,
Fede

Re: poor scrolling in qemu-kvm

[Andreas Enge]

On Mon, Dec 01, 2014 at 09:20:49AM +0100, Federico Beffa wrote:
> It sounds like you did quite some work on it already.  Please go on if
> you like. I'm not trying to step on anyone's feet :-)

Difficult to step on anyone's feet by doing work ;-)

I am definitely not going to work on "guix refresh" in the near future.

I could work on updating x.org, but not before next year, or maybe leisurely
during Christmas holidays.

Andreas

Re: poor scrolling in qemu-kvm

[Ludovic Courtès]

ludo@gnu.org (Ludovic Courtès) skribis:

> The right thing is to use ‘-vga std’, which uses a “standard VGA”
> emulator, which doesn’t have this problem.
>
> However, X will fail to start currently when using this.

Somehow this problem disappeared recently, and running X in -vga std
works fine as of commit b2bd7c2.

I’ll update the VM code to use that by default.

Ludo’.