Re: [Xen-devel] opengl=1?

["Jun Koi" <junkoi2004@xxxxxxxxx>]

On Thu, Dec 11, 2008 at 8:11 PM, Stefano Stabellini
<stefano.stabellini@xxxxxxxxxxxxx> wrote:
> Jun Koi wrote:
>
>> On Thu, Dec 11, 2008 at 7:33 PM, Stefano Stabellini
>> <stefano.stabellini@xxxxxxxxxxxxx> 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

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