Xen users - Jun 2007 - Does faster 2D Host video card help HVM guest?

In the next week I hope to install Xen 3.10 on a ASUS
M2V-MX - AMD Athlon 64 X2 based system.  The board has
onboard S3 video. I will be running HVM type guests
(2D graphics only).

How important is the performance of the host video
card to guest video performance?

Will a medium performance video card like the ATI
X1600 improve guest video over that of the onboard
video?

What host video spec are important?

Will a 3D card help HVM guest 2D performance?

thanks


       
____________________________________________________________________________________
Boardwalk for $500? In 2007? Ha! Play Monopoly Here and Now (it''s
updated for today''s economy) at Yahoo! Games.
http://get.games.yahoo.com/proddesc?gamekey=monopolyherenow  

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Because of how the qemu-dm graphics card emulation works, I believe host
graphics card speed has pretty much no impact whatsoever with the current
device model. The important factors are host CPU & RAM speed.

/Trolle

On 6/3/07, ecs user <user_ecs@yahoo.com> wrote:
>
> r.
> In the next week I hope to install Xen 3.10 on a ASUS
> M2V-MX - AMD Athlon 64 X2 based system.  The board has
> onboard S3 video. I will be running HVM type guests
> (2D graphics only).
>
> How important is the performance of the host video
> card to guest video performance?
>
> Will a medium performance video card like the ATI
> X1600 improve guest video over that of the onboard
> video?
>
> What host video spec are important?
>
> Will a 3D card help HVM guest 2D performance?
>
> thanks
>
>
>
>
>
____________________________________________________________________________________
> Boardwalk for $500? In 2007? Ha! Play Monopoly Here and Now (it''s
updated
> for today''s economy) at Yahoo! Games.
> http://get.games.yahoo.com/proddesc?gamekey=monopolyherenow
>
> _______________________________________________
> Xen-users mailing list
> Xen-users@lists.xensource.com
> http://lists.xensource.com/xen-users
>

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> Because of how the qemu-dm graphics card emulation works, I believe host
> graphics card speed has pretty much no impact whatsoever with the current
> device model. The important factors are host CPU & RAM speed.
Right now, the guest''s graphics performance is going to be fairly slow 
whatever you''re running in the host.  It''s not worth trying to
upgrade the
host graphics card, because it''s not really going to make any
difference to
the guest.

Guest display improvements will probably come from future optimisations in 
future releases of Xen.

Cheers,
Mark

-- 
Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
Mark: To answer a question with a question: What use is a skateboard?
Dave: Skateboards have wheels.
Mark: My wheel has a wheel!

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I recently measured graphics performance on an OS/2 guest (which is as
"unaccellerated" as it can get) and discovered, much to my surprise,
that
graphics performance is nowhere near as bad as one might assume, and in fact
pretty good. I believe the explanation to be that though unacellerated, the
virtual graphics card is sitting on a "bus" that actually has the full
speed
of RAM, which on a fast dual channel DDR2 system is actually faster than
even PCIe 16x. Moroever, due to the fact that the cirrus device model uses
buffered mmio, in a multi-core system, a certain amount of the "work"
can
get handed off to dom0 and the other CPU core.
It would seems to me that the main reason 2D & gui ops feel "slow"
in guests
right now is the fact that even with SDL, the guest VM''s screen is only
updated  at 30 Hz.

/Trolle

On 6/4/07, Mark Williamson <mark.williamson@cl.cam.ac.uk>
wrote:
>
> > Because of how the qemu-dm graphics card emulation works, I believe
host
> > graphics card speed has pretty much no impact whatsoever with the
> current
> > device model. The important factors are host CPU & RAM speed.
>
> Right now, the guest''s graphics performance is going to be fairly
slow
> whatever you''re running in the host.  It''s not worth
trying to upgrade the
> host graphics card, because it''s not really going to make any
difference
> to
> the guest.
>
> Guest display improvements will probably come from future optimisations in
> future releases of Xen.
>
> Cheers,
> Mark
>
> --
> Dave: Just a question. What use is a unicyle with no seat?  And no pedals!
> Mark: To answer a question with a question: What use is a skateboard?
> Dave: Skateboards have wheels.
> Mark: My wheel has a wheel!
>

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> -----Original Message-----
> From: xen-users-bounces@lists.xensource.com 
> [mailto:xen-users-bounces@lists.xensource.com] On Behalf Of 
> Trolle Selander
> Sent: 04 June 2007 10:58
> To: xen-users@lists.xensource.com
> Subject: Re: [Xen-users] Does faster 2D Host video card help 
> HVM guest?
> 
> I recently measured graphics performance on an OS/2 guest 
> (which is as "unaccellerated" as it can get) and discovered, 
> much to my surprise, that graphics performance is nowhere 
> near as bad as one might assume, and in fact pretty good. I 
> believe the explanation to be that though unacellerated, the 
> virtual graphics card is sitting on a "bus" that actually has 
> the full speed of RAM, which on a fast dual channel DDR2 
> system is actually faster than even PCIe 16x. Moroever, due 
> to the fact that the cirrus device model uses buffered mmio, 
> in a multi-core system, a certain amount of the "work" can 
> get handed off to dom0 and the other CPU core. 
> It would seems to me that the main reason 2D & gui ops feel 
> "slow" in guests right now is the fact that even with SDL, 
> the guest VM''s screen is only updated  at 30 Hz.
Yes, the "slowness" in graphics is more about update frequency than to
do with the actual "read/write" performance of the "graphics
adapter".
The way it works (for those inclined to wanting to know these things) is
that the frame-buffer is shared between qemu-dm and the guest. So data
can be read/written with normal RAM-speed, as Trolle says. To preserve
CPU-performance on qemu-dm, updates are rate-limited, because the method
to update the screen is that we read the frame-buffer, and compare it
with an "old" frame buffer [I believe it''s actually a
check-sum, rather
than byte by byte compare (ok, technically, it''s also using SSE
instructions to get as good a throughput as possible)]. Doing this at
50-100Hz would consume a lot more than the current CPU consumption of
qemu-dm. 

--
Mats
> 
> /Trolle
> 
> 
> On 6/4/07, Mark Williamson <mark.williamson@cl.cam.ac.uk> wrote:
> 
> 	> Because of how the qemu-dm graphics card emulation 
> works, I believe host
> 	> graphics card speed has pretty much no impact 
> whatsoever with the current
> 	> device model. The important factors are host CPU & RAM speed. 
> 	
> 	Right now, the guest''s graphics performance is going to 
> be fairly slow
> 	whatever you''re running in the host.  It''s not worth 
> trying to upgrade the
> 	host graphics card, because it''s not really going to 
> make any difference to 
> 	the guest.
> 	
> 	Guest display improvements will probably come from 
> future optimisations in
> 	future releases of Xen.
> 	
> 	Cheers,
> 	Mark
> 	
> 	--
> 	Dave: Just a question. What use is a unicyle with no 
> seat?  And no pedals! 
> 	Mark: To answer a question with a question: What use is 
> a skateboard?
> 	Dave: Skateboards have wheels.
> 	Mark: My wheel has a wheel!
> 	
> 
> 
> 


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