opengl=1?

opengl=1?

[Jun Koi]

Hi,

I found that we have an option named opengl. What is that for? So if I
put "opengl=1" in my VM configuration file, what advantage my VM will
get??

Thanks,
Jun

Re: opengl=1?

[Stefano Stabellini]

Jun Koi wrote:

> Hi,
> 
> I found that we have an option named opengl. What is that for? So if I
> put "opengl=1" in my VM configuration file, what advantage my VM will
> get??
> 

opengl=1 is the default and makes qemu render the guest framebuffer
using opengl.
Otherwise if you set opengl=0 qemu will use the sdl library.
opengl=1 makes sense if you don't use vnc and you have good drivers for
your graphic card in dom0.

Re: opengl=1?

[Jun Koi]

On Thu, Dec 11, 2008 at 7:33 PM, Stefano Stabellini
<stefano.stabellini@eu.citrix.com> wrote:
> Jun Koi wrote:
>
>> Hi,
>>
>> I found that we have an option named opengl. What is that for? So if I
>> put "opengl=1" in my VM configuration file, what advantage my VM will
>> get??
>>
>
> opengl=1 is the default and makes qemu render the guest framebuffer
> using opengl.

OK, so the patch you posted on QEMU mailing list is to enable this
function on QEMU.

> Otherwise if you set opengl=0 qemu will use the sdl library.
> opengl=1 makes sense if you don't use vnc

So this means "opengl=1" (default) and "vnc=0" will give a better
performance than "vnc=1, sdl=0", right?

>and you have good drivers for
> your graphic card in dom0.

I am using Ubuntu 8.10 with chipset Intel 945GM, so certainly I have
"good driver", right?

Many thanks,
Jun

Re: opengl=1?

[Stefano Stabellini]

Jun Koi wrote:

> On Thu, Dec 11, 2008 at 7:33 PM, Stefano Stabellini
> <stefano.stabellini@eu.citrix.com> wrote:
>> Jun Koi wrote:
>>
>>> Hi,
>>>
>>> I found that we have an option named opengl. What is that for? So if I
>>> put "opengl=1" in my VM configuration file, what advantage my VM will
>>> get??
>>>
>> opengl=1 is the default and makes qemu render the guest framebuffer
>> using opengl.
> 
> OK, so the patch you posted on QEMU mailing list is to enable this
> function on QEMU.

Yes.

>> Otherwise if you set opengl=0 qemu will use the sdl library.
>> opengl=1 makes sense if you don't use vnc
> 
> So this means "opengl=1" (default) and "vnc=0" will give a better
> performance than "vnc=1, sdl=0", right?


Just to be clear opengl is used only together with sdl: sdl is still
needed to create the window.
So the three possibilities are:

/* window on the host screen, opengl acceleration */
sdl=1 opengl=1 vnc=0

/* window on the host screen, no opengl acceleration */
sdl=1 opengl=0 vnc=0

/* no window on the host screen just a vnc server */
sdl=0 (opengl does not matter) vnc=0

 
>> and you have good drivers for
>> your graphic card in dom0.
> 
> I am using Ubuntu 8.10 with chipset Intel 945GM, so certainly I have
> "good driver", right?
> 

If you are using the intel driver (intel, i815, i915, etc.) in xorg,
yes; if you are using the vesa driver, no.

If you are using opengl=1 and the vesa driver in xorg, you'll notice
because it is really slow.

Re: opengl=1?

[Jun Koi]

On Thu, Dec 11, 2008 at 8:11 PM, Stefano Stabellini
<stefano.stabellini@eu.citrix.com> wrote:
> Jun Koi wrote:
>
>> On Thu, Dec 11, 2008 at 7:33 PM, Stefano Stabellini
>> <stefano.stabellini@eu.citrix.com> wrote:
>>> Jun Koi wrote:
>>>
>>>> Hi,
>>>>
>>>> I found that we have an option named opengl. What is that for? So if I
>>>> put "opengl=1" in my VM configuration file, what advantage my VM will
>>>> get??
>>>>
>>> opengl=1 is the default and makes qemu render the guest framebuffer
>>> using opengl.
>>
>> OK, so the patch you posted on QEMU mailing list is to enable this
>> function on QEMU.
>
> Yes.
>
>>> Otherwise if you set opengl=0 qemu will use the sdl library.
>>> opengl=1 makes sense if you don't use vnc
>>
>> So this means "opengl=1" (default) and "vnc=0" will give a better
>> performance than "vnc=1, sdl=0", right?
>
>
> Just to be clear opengl is used only together with sdl: sdl is still
> needed to create the window.
> So the three possibilities are:
>
> /* window on the host screen, opengl acceleration */
> sdl=1 opengl=1 vnc=0
>

OK, and this gives us the best performance.

> /* window on the host screen, no opengl acceleration */
> sdl=1 opengl=0 vnc=0
>
> /* no window on the host screen just a vnc server */
> sdl=0 (opengl does not matter) vnc=0
>
>
>>> and you have good drivers for
>>> your graphic card in dom0.
>>
>> I am using Ubuntu 8.10 with chipset Intel 945GM, so certainly I have
>> "good driver", right?
>>
>
> If you are using the intel driver (intel, i815, i915, etc.) in xorg,
> yes; if you are using the vesa driver, no.
>
> If you are using opengl=1 and the vesa driver in xorg, you'll notice
> because it is really slow.

So I understand that if your patches to QEMU are merged, QEMU/KVM
would get much better graphical performance. Excellent! Did you
benchmark to see how much it is better? Any number?

Thanks,
Jun

Re: opengl=1?

[Stefano Stabellini]

Jun Koi wrote:

>> /* window on the host screen, opengl acceleration */
>> sdl=1 opengl=1 vnc=0
>>
> 
> OK, and this gives us the best performance.

Yes.

> 
> So I understand that if your patches to QEMU are merged, QEMU/KVM
> would get much better graphical performance. Excellent! Did you
> benchmark to see how much it is better? Any number?
> 


Yes, but don't hold your breath, qemu people didn't seem very interested
in this.
It is difficult to get any significant number, but I can tell you that
at least you can get window resizing for free, not to mention many
possible further improvements.