Author Topic: Debian 10 vs CentOS 7 (both as VM under Fedora 32 KVM)  (Read 93 times)

cchinicz

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Debian 10 vs CentOS 7 (both as VM under Fedora 32 KVM)
« on: July 24, 2020, 09:23:51 am »
Hi,

I'm running Fedora 32 on my host (32GB RAM) and I have two VMs under KVM: Debian 10 and CentOS 7, both with 4GB RAM and 4 vCPUs.

With Debian, even the cursor moves with a delay when I move the mouse and all applications seems to be slower than usual. With CentOS it's just like on the host, I cannot perceive any difference in the user experience.

Any idea why Debian port does not seem to run "natively" while CentOS runs just ok? Is it because some "better" integration between host (which is Fedora) and CentOS? Shouldn't KVM see any guest the same way?

Appreciate any feed-back.

Thanks

MPC7500

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Re: Debian 10 vs CentOS 7 (both as VM under Fedora 32 KVM)
« Reply #1 on: July 24, 2020, 10:16:30 am »
Which Debian image do you use?

cchinicz

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Re: Debian 10 vs CentOS 7 (both as VM under Fedora 32 KVM)
« Reply #2 on: July 24, 2020, 10:37:37 am »
debian-10.4.0-ppc64el-xfce-CD-1

pocock

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Re: Debian 10 vs CentOS 7 (both as VM under Fedora 32 KVM)
« Reply #3 on: July 24, 2020, 10:56:01 am »
If you connect to the Debian VM with SSH, how is the performance of the command line?

Can you try to use X forwarding over SSH to see how one of the apps in the Debian VM behaves when its window is on the Fedora host X display?

Have you checked journalctl and the X server log in the Debian VM?

Which X server process in each case (Fedora host, CentOS and Debian)?

When you write "slower", do you mean the GUI is slow but applications are running at expected speed?  Or the applications actually run slowly when you do something with no visual output, e.g. zipping a large file is the same speed in every VM and host?
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cchinicz

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Re: Debian 10 vs CentOS 7 (both as VM under Fedora 32 KVM)
« Reply #4 on: July 24, 2020, 11:16:18 am »
Hi,

I use both VMs through the GUI, I'm just a regular desktop user.

Regarding slowness, your question kind of answer the issue: the slowness is related to the GUI and not the applications themselves. I've tried them both again, paying attention to application start time and responsiveness and they seem to be ok and similar (actually, Firefox starts much faster on Debian than on CentOS). The issue is just this sluggishness of the cursor when I move the mouse around the screen on the Debian VM.

Maybe it's something related to how these VMs connect to the display? By the way, I'm using both VMs at 1920x1080.

Regards

pocock

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Re: Debian 10 vs CentOS 7 (both as VM under Fedora 32 KVM)
« Reply #5 on: July 24, 2020, 11:31:39 am »
Even as a desktop user, there is always a display server in your system

It is really useful to find out, for example, if it is X or Wayland:

You can run this command in Fedora and each VM:

$ echo $XDG_SESSION_TYPE

You can get more information in each system by looking at the output of

$ xdpyinfo

In the Debian system, you can look at this file and search for errors:

/var/log/Xorg.0.log

Any line with WW is a warning and EE is an error

Here is an example error from that file:

[    98.019] (EE) Failed to load module "glx" (loader failed, 0)

The more details you share from that file, the easier it is to help you.

I suspect the problem you have is not a problem with the ppc64el architecture, it could be something related to X or Wayland and you might want to ask in the Debian IRC channels to see if anybody can help troubleshoot.
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cchinicz

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Re: Debian 10 vs CentOS 7 (both as VM under Fedora 32 KVM)
« Reply #6 on: July 25, 2020, 01:57:57 pm »
Hi,

echo $XDG_SESSION_TYPE
On host (Fedora): tty
On Debian VM: wayland
On Centos: x11

The file /var/log/Xorg.0.log did not exist on the Debian VM (I've tried vi /var/log/Xorg.0.log and it opened a new file).

Thanks

pocock

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Re: Debian 10 vs CentOS 7 (both as VM under Fedora 32 KVM)
« Reply #7 on: July 25, 2020, 03:02:39 pm »

That tells me that Debian is using Wayland.  You can disable Wayland in Debian so that it uses Xorg, like the Centos host.  There are lots of pages with information about how to do that

https://duckduckgo.com/?q=debian+disable+wayland

Please give feedback if this solves the problem for you, it is most likely a Wayland problem and not a PPC problem.
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cchinicz

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Re: Debian 10 vs CentOS 7 (both as VM under Fedora 32 KVM)
« Reply #8 on: July 27, 2020, 06:17:07 am »
Hi,

I've tried to edit /etc/gdm3/daemon.conf to uncomment #WaylandEnable=flalse but my Debian is not allowing me to add my user to sudoers. On CentOS I added my users to sudoers logging as root but on Debian I could not find how to add my user to sudoers neither how to login in as root or open a terminal as root.

I've tried reinstalling Debian but ended up with the same issue.

Any idea of how to circumvent this limitation?

Thanks

pocock

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Re: Debian 10 vs CentOS 7 (both as VM under Fedora 32 KVM)
« Reply #9 on: July 29, 2020, 12:36:28 am »

Are you able to access the Debian VM through a text console, for example, by starting at a different run level or using the CTRL-ALT-F3 keystroke in the VM?

If that doesn't work, I would suggest asking for help through the Debian IRC channels, somebody can help you with that step-by-step

https://wiki.debian.org/IRC
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cchinicz

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Re: Debian 10 vs CentOS 7 (both as VM under Fedora 32 KVM)
« Reply #10 on: July 29, 2020, 01:18:09 am »
Hi,

Thanks! I solved the issue and edited the /etc/gdm3/daemon.conf file and uncommented #WaylandEnable=flalse.

After restarting everything works fine, no sluggishness anymore.

Cheers