[pve-devel] qemu 1.4 and usb-tablet

[Alexandre DERUMIER]

I have just send a patch to enable usb2 as default and hotplug/unplug usb-tablet on demand on console open.



----- Mail original ----- 

De: "Alexandre DERUMIER" <aderumier at odiso.com> 
À: "Dietmar Maurer" <dietmar at proxmox.com> 
Cc: pve-devel at pve.proxmox.com 
Envoyé: Lundi 18 Février 2013 05:20:02 
Objet: Re: [pve-devel] qemu 1.4 and usb-tablet 

I had tried to connect usb-tablet on ehci, 

with 2003/2008 && debian guests, I have around 2% lower cpu on my old xeon. 

Which is good, with a lot of vms, that can be an huge benefit. 

I have also tried live migration of ehci, it's works perfectly now. 
So maybe can we switch to full usb2 ? (I think all os support usb2 natively since at least 10years, like win2003) 


Another thing we could do to use less cpu with usb-tablet, is to plug-in it dynamically 
when we launch console (device_add). 
But I don't know to detect when to remove it. (how to detect session/console close ?). 

Without tablet I have 4% more less cpu on this same xeon. 

----- Mail original ----- 

De: "Alexandre DERUMIER" <aderumier at odiso.com> 
À: "Dietmar Maurer" <dietmar at proxmox.com> 
Cc: pve-devel at pve.proxmox.com 
Envoyé: Dimanche 17 Février 2013 16:19:07 
Objet: Re: [pve-devel] qemu 1.4 and usb-tablet 

>>Any idea who we can use that? 

Simply connect the usb-tablet to ehci controller ? 

Maybe is it time to use ehci by default ? (It's migratable now). 
And seem that is use lower cpu (maybe less interrupts ?) 

the qemu git commit is here : 

http://git.qemu.org/?p=qemu.git;a=commit;h=427e3aa151c749225364d0c30640e2e3c1756d9d 

" 
usb-tablet: Allow connecting to ehci 



Our ehci code has is capable of significantly lowering the wakeup rate 

for the hcd emulation while the device is idle. It is possible to add 

similar code ot the uhci emulation, but that simply is not there atm, 

and there is no reason why a (virtual) usb-tablet can not be a USB-2 device. 



Making usb-hid devices connect to the emulated ehci controller instead 

of the emulated uhci controller on vms which have both lowers the cpuload 

for a fully idle vm from 20% to 2-3% (on my laptop). 



An alternative implementation to using a property to select the tablet 

type, would be simply making it a new device type, ie usb-tablet2, but the 

downside of that is that this will require libvirt changes to be available 

through libvirt at all, and then management tools changes to become the 

default for new vms, where as using a property will automatically get 

any pc-1.3 type vms the lower cpuload." 


----- Mail original ----- 

De: "Dietmar Maurer" <dietmar at proxmox.com> 
À: pve-devel at pve.proxmox.com 
Envoyé: Dimanche 17 Février 2013 15:44:01 
Objet: [pve-devel] qemu 1.4 and usb-tablet 

I already updated our git to include the new qemu 1.4 code. 

>From the changelog: 
> * usb: usb-tablet can be connected as an USB 2.0 device, lowering the CPU 
> usage substantially 

Any idea who we can use that? 


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