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Re: [Xen-users] Xen linux and gaming box

On Fri, Sep 28, 2012 at 2:09 PM, Karim Sanjabi <karim@xxxxxxxxxxxxxxxxx> wrote:
My first post, so please let me know if this is the wrong place for this newbie stuff. Been reading Xen ideas, docs, post for a couple months and decided to give this a shot.

Goal: Run any Ubuntu derivative off an intel i5 video card and play Windows 7 games on an Nvidia gtx 570 through vga pass through.  Use a simple dvi toggle switch on the monitor (2 inputs) to go between them.

Hardware: 16g ram, i5 (non K), vt-d ASRock motherboard, Intel ssd 120 gig, and lots of other slower drives.

So my few questions are:

1) Is there any dis-advantage between Dom0 Mint/Ubuntu/Debian/Fedora ? Performance, stability? Was assuming to compile in the latest xen unstable for the best shot at nvidia support.

1. Go with what you feel most comfortable with, which sounds like Ubuntu.  I had successfully used Debian, tried Mint but didn't like it as much so I went back to Debian.  The biggest disadvantage will be forcing yourself to configure an operating system you are not familiar with.

2) What is the best disk performance I can get with a windows 7 DomU? Pass a controller though or just share it with dom0 and maybe another domU.

2. You said SSD for your host, are you planning to use LVM on the SSD or on a regular HDD?  I use an OCZ Vertex 3 with LVM, and a logical volume for Windows.  Windows Experience Index was 6.6, but after installing GPLPV drivers jumped to 7.7 and performs at near-native speeds.  I would imagine similar results from HDD performance. 

3) Seems like the recommendation is to not have an GUI on Dom0.  is there any reason for this? Ideally would like to run XFCE for Ubuntu. I don't understand the pros/cons of running XFCE on an ubuntu dom0 vs running it on a DomU
3. Assuming best practices, you normally would install as little as possible on Dom0 and only use it as a control OS.  However, as a home use I did just the opposite and use Gnome3 with Debian and Intel's on-die GPU.  From what I read XFCE is a light-weight GUI, so that should probably work great. 

4) Is it required to pass through a usb bus with a 2nd keyboard/mouse or kvm switch? Or Can I just share the keyboard mouse?  If I do need a kvm switch, will any of them work or is there an approved list (couldn't find any). Little unclear on how to switch between DomU instances (that what cntrl-] does?)
4. Supposedly you can pass individual USB devices, but they perform at USB 1.1 speeds.  For best results and reliability, pass a controller.  You could use VNC to pass input from Dom0 to DomU, but that'd probably be difficult.  If by switching DomU instances you mean using the KVM to switch controls then that might work well with passed USB controllers. 
5) For allocating ram and cpu. How much do I need to leave for dom0? Guessing 2 cores for win 7, 2 cores for ubuntu, 8 gigs each may not work since I get the impression I must leave some resources for dom0.  Can the dom0 and ubuntu domU be shared with say 2 cores 8 gigs?

5. I will try to answer this, but someone else will probably have better or more accurate advice.

Dom0 will take all the RAM by default, and assign as many vcores as available (eg. Core i7 Hyperthreading 4 cores, 8vcores, i5 will probably get 4 vcores).

By default Xen uses ballooning which when you attempt to launch an HVM it will free up as much RAM as necessary from Dom0.  I encountered problems with the speed at which it was able to free up RAM, and had to set a limit at boot time.  I did not turn off ballooning because when Windows is not running Dom0 can ask for more RAM from Xen.

I run Windows with 4 vcores, when I turn it on Dom0 still retains 8 vcores.  I don't limit Dom0 vcores because as mentioned when I turn off Windows I use Dom0.  The vcores are shared, and not subject to the same limitations as strict cpu assignment; I have never needed strict assignment for performance, so I would try 2 or 4 vcores and if that doesn't work maybe someone will give you a run through on strict cpu assignment.

Thanks ahead of time. These answers have been very hard to find and understand.


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