use_usb_tablet=true have no effect

[Thiago Martins]

Hello Stackers!

I'm trying to enable the "usb tablet" to see if it improve my Windows guests but, it have not effect.

Steps to reproduce:

1- Install Ubuntu 14.04.1 with IceHouse;

2- Enable the following line at /etc/nova/nova-compute.conf, under [libvirt] group:

---
use_usb_tablet=true
---

3- Start a guest (Windows 2k8 R2), go to its compute node to verify the VM configuration file with:

---
virsh dumpxml instance-XXXXWWWZ
---

...There is no "usb tablet" there.

I tried to put "use_usb_tablet=true" under [DEFAULT], under nova.conf, still no luck.

Thanks in advance!

Regards,
Thiago

[Davanum Srinivas (DIMS) (dims-v)]

Thiago,

Did you get a chance to look at how/when the switch is used in the code?
https://github.com/openstack/nova/blob/master/nova/virt/libvirt/driver.py#L3407

Maybe you will spot a combination of flags that will work for you

-- dims

[Sahid Orentino (sahid-ferdjaoui)]

As dims said we need to know you configuration about vnc or spice

[Thiago Martins (martinx)]

Hello Dims, Sahid,

Thanks for this fast reply! :-)

I'm using KVM as hypervisor (Compute Node), and with SPICE Consoles + SPICE Agent installed on Windows guest (I'm not using VNC anymore).

That line 3407 you presented, it have:

"... and guest.os_type == vm_mode.HVM"

so, I think that KVM is "vm_mode.HVM", am I right?!

The compute configuration is (nova.conf):

---
vnc_enabled = False
novnc_enabled = False

[spice]
enabled = True
agent_enabled = True
html5proxy_base_url = http://controller-1.domain.com.br:6082/spice_auto.html
keymap = en-us
server_listen = ::
server_proxyclient_address = cnode-1.mng.domain.com.br
---

Thanks!!

[Thiago Martins (martinx)]

Moving from "Incomplete -> New", since I posted the missing info.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/120264

[Daniel Berrange (berrange)]

The SPICE agent provides a transport channel for mouse events which is better than USB tablet as it avoids the high CPU burn that USB tablet suffers from. So when SPICE agent is enabled, avoiding USB tablet is desirable to cut the baseline CPU usage of VMs and thus increase overall host CPU capacity / VM density per host.

Of course the logic that Nova applies here is not 100% ideal - there will always be some portion of scenarios which may want to keep the USB tablet, but on balance disabling it is a win in general. We likely want to make it possible to override the default behaviour based on an image property, but keep USB disabled by default when SPICE agent is on.

[Thiago Martins (martinx)]

Hi Daniel,

You answer is very complete, I think you guys can mark this BUG as
"Invalid"...

Thanks!
Thiago

On 10 September 2014 07:55, Daniel Berrange <email address hidden>
wrote:

> The SPICE agent provides a transport channel for mouse events which is
> better than USB tablet as it avoids the high CPU burn that USB tablet
> suffers from. So when SPICE agent is enabled, avoiding USB tablet is
> desirable to cut the baseline CPU usage of VMs and thus increase overall
> host CPU capacity / VM density per host.
>
> Of course the logic that Nova applies here is not 100% ideal - there
> will always be some portion of scenarios which may want to keep the USB
> tablet, but on balance disabling it is a win in general. We likely want
> to make it possible to override the default behaviour based on an image
> property, but keep USB disabled by default when SPICE agent is on.
>
> --
> You received this bug notification because you are subscribed to the bug
> report.
> https://bugs.launchpad.net/bugs/1356633
>
> Title:
> use_usb_tablet=true have no effect
>
> To manage notifications about this bug go to:
> https://bugs.launchpad.net/nova/+bug/1356633/+subscriptions
>

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/120264
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=78294b9ecf4382a51bc312834228c1d4ec789c1b
Submitter: Jenkins
Branch: master

commit 78294b9ecf4382a51bc312834228c1d4ec789c1b
Author: Sean Dague <email address hidden>
Date: Tue Sep 9 18:06:38 2014 -0400

    document why we disable usb_tablet in code

    This provides a code level explanation for why we disregard the user
    option for use_usb_tablet when the spice agent is enabled. It came up
    in a bug report, and having the comment close to the code helps carry
    the information forward.

    Change-Id: I7945e921b6283519d91e234584d99d9e82218e6d
    Closes-Bug: #1356633