AMD-Vi and Intel VT-d, difference in VMs?

[Obsoleet]

For those of you who have used VMs before the advent of AMD-Vi and Intel VT-d, did you notice a significant difference in your VMs speed?

I'm considering updating my CPU just for this feature, but want to know if it removes lagginess in VMs. I'm happy with the VM performance on my Q9450 for what I do, but if it's a native experience using an updated processor I might do that earlier than I 'need' to.

Currently looking at going for an AMD A10 on the desktop, and was pretty set on an i3 for laptop but the i3s lack VT-d and the i5s are out of the price range I'm looking at. So likely looking at an AMD A8 for mobile. Same price as the i3's I'm looking at, but has AMD-Vi.

If there's any disparity between running VMs in VB between an i5 and Ax CPU please let me know. I'd be interested in knowing, from what I've read though they seem generally on-par at this point.

 

[BrightCandle]

Vt-d is all about IO CPU usage. In theory it wont actually improve performance unless you are fully utilising the CPU and then start to do some IO. Its also meant to make quite a big difference when there are multiple VM's running and sharing the same devices.

I could run some CrystalDiskMark tests etc to see if it makes any real difference for a single SSD in terms of CPU usage or actual benchmark performance but according to Intel its only going to make a difference at threshold levels of performance.

 

[Obsoleet]

Thanks for that. I think you may be right.

I was doing some searching and it sounds like for quite some time now with AMD processors you get every virtualization feature. While with Intel they segment it off, as I discovered with the i3s.

http://www.semiaccurate.com/forums/showthread.php?t=2141

That, sucks. While I couldn't give a crap less about the Intel advantage in CPU performance, I do want AMD's superior GPU and having the same performance in VM's as Intels 'full VM platform', the i5 across all it's CPU lineup is a great addition.

Unless some of you have some experience and insights with AMD and Intel VMs, before and after vt-d/AMD-Vi and so forth, I'll probably just stick with AMD going forward. No reason not to, and I use VMs all the time.

 

[itsmydamnation]

it makes a difference on anything that is I/O latency senseitive, like real time media/IPTV streaming etc.

 

[Obsoleet]

I'd love to see it in action vs my current rig.. I didn't think about it but I do have an Ivy Bridge i5 laptop.. I'll fire up a simple Ubuntu VM and report back what I find vs my old Q9450. At least that will definitively answer if a newer CPU with all these features does indeed run a VM better.

I'm going to to replace my desktop and laptop with Kaveri if possible.
If either breaks before then I'll probably go for Trinity, an A8 laptop and A10 mobile.

 

[ShintaiDK]

Rememebr AMD-Vi/VT-D requies not only the CPU, but also the BIOS and chipset to support it as well.

For AMD-V/VT-X, then Intels solution got lower overhead.
Example, just with Intel tho:
http://images.anandtech.com/reviews/cpu/intel/Haswell/Architecture/VT.jpg

 

[Insert_Nickname]

I was doing some searching and it sounds like for quite some time now with AMD processors you get every virtualization feature. While with Intel they segment it off, as I discovered with the i3s.

Ironically enough, the K-series does not support VT-d. But as Shintai pointed out you STILL need chipset/BIOS support.

 

[Abwx]

Example, just with Intel tho:
http://images.anandtech.com/reviews/cpu/intel/Haswell/Architecture/VT.jpg

A slide of Broadwell should exhibit even better caracteristics....

 

[nehalem256]

http://en.wikipedia.org/wiki/VT-d#I.2FO_MMU_virtualization_.28AMD-Vi_and_VT-d.29

An input/output memory management unit (IOMMU) enables guest virtual machines to directly use peripheral devices, such as Ethernet, accelerated graphics cards, and hard-drive controllers, through DMA and interrupt remapping. This is sometimes called PCI passthrough.[31] Both AMD and Intel have released specifications

Isn't VT-d just for PCI passthrough?

So unless you started assigning device in your PC to just your VM you won't enjoy any benefit of VT-d.

 

[Insert_Nickname]

Isn't VT-d just for PCI passthrough?

So unless you started assigning device in your PC to just your VM you won't enjoy any benefit of VT-d.

More or less. But the OP wrote that he wanted EVERY virtualization feature...

I don't know if FM2 supports IOMMU though. AM3+ does if there is CPU/chipset/BIOS support...

 

[ShintaiDK]

More or less. But the OP wrote that he wanted EVERY virtualization feature...

I don't know if FM2 supports IOMMU though. AM3+ does if there is CPU/chipset/BIOS support...

AM3+ needs 890FX or 9 series plus actual BIOS support.

 

[Abwx]

The Input/Output Memory Management Unit (IOMMU) now also allows IO/dGPU shaders to operate directly in the main memory.

http://www.hitechlegion.com/reviews/processors/30951-amd-a10-5800k?start=1

 

[holden j caufield]

I noticed almost no speed difference in my vms going from vt-x to vt-x/d compatible processor, relative to the processor (core 2 duo t9300 ran my vms just about as good as my i5 520m, 520m ran it probably a little better mostly because it was a better cpu). The difference is that with amd-vi and intel vt-d is I could passthrough devices such as raid controllers, straight to my vm. So in that sense my storage is faster. I think the main advantage is that you can passthrough a video card so it's native, raid controller, network controller etc. Else I've found esx 5, hyper-v and vmware workstation to perform similar with vt-d enabled or disabled on my laptop. Though I didn't benchmark it.

I have a 1045t and 990fxa that passthrough works well on. You need to check ark intel because a number of intel chips have vt-d disabled. I've heard of past quad core 2 duo chips with the right motherboard doing vt-d (when memory management was on the motherboard) now with the i series it's on the cpu so ark intel needs to be checked.

I found intel ept more useful as you can run nested vms.

 

[Piotrsama]

I found this, don't know if it's complete.
http://en.wikipedia.org/wiki/IOMMU_hardware_list

edit: (the list of compatible mobos, I meant)

I was going to buy the Asus M5A99FX pro R2.0... but can't really find if it supports IOMMU, so probably will end up going with the Sabertooth.

 

[Fox5]

The VM extensions make a big difference, provided you have hardware with an integrated memory controller. (older hardware sucked)

I can't speak for VMware, but in Virtualbox, multicore cpu performance sucks without them, and you can't use the faster device hardware (ICH9 chipset etc) without them.
The iommu VM extensions don't work under Windows afaik, you need Linux.

 

[Obsoleet]

Ironically enough, the K-series does not support VT-d. But as Shintai pointed out you STILL need chipset/BIOS support.

So if the K series doesn't, I'm guessing the M series doesn't either? And I'm guessing it's more difficult to find if a laptop supports it than a desktop.

The VM extensions make a big difference, provided you have hardware with an integrated memory controller. (older hardware sucked)

I can't speak for VMware, but in Virtualbox, multicore cpu performance sucks without them, and you can't use the faster device hardware (ICH9 chipset etc) without them.
The iommu VM extensions don't work under Windows afaik, you need Linux.

So with a new rig, and I better off running Linux native and Windows in a VM? The only thing I use Windows for is gaming, and if gaming under a VM is sufficient I'd be happy to do that.

 

[ShintaiDK]

So if the K series doesn't, I'm guessing the M series doesn't either? And I'm guessing it's more difficult to find if a laptop supports it than a desktop.



So with a new rig, and I better off running Linux native and Windows in a VM? The only thing I use Windows for is gaming, and if gaming under a VM is sufficient I'd be happy to do that.

http://ark.intel.com/

Just check here, plenty of M series support it. K series are just overclocking CPUs.

And a graphics card is covered under VT-D/AMD-V if I recall right. And network cards are covered under VT-C and not sure if AMD got any equalent.

 

[Piotrsama]

Hm... according to this list only 2 VM software use VT-d and no one uses AMD-Vi.
http://en.wikipedia.org/wiki/Comparison_of_platform_virtual_machines

 

[PingSpike]

Has anyone actually used a 3D card under a windows guest VM with this feature? I was reading about it yesterday and it seemed like only PCI cards and a handful of PCI-e cards even worked for most platforms. The exception being Xen which runs on the bare metal as the host. But the articles I was reading were a little bit old so the picture may well have changed.

 

[holden j caufield]

Hm... according to this list only 2 VM software use VT-d and no one uses AMD-Vi.
http://en.wikipedia.org/wiki/Comparison_of_platform_virtual_machines

I've been using amd 1045t and 990fxa-ud3 iommu to passthrough devices on esx 5

 

[Fox5]

So if the K series doesn't, I'm guessing the M series doesn't either? And I'm guessing it's more difficult to find if a laptop supports it than a desktop.



So with a new rig, and I better off running Linux native and Windows in a VM? The only thing I use Windows for is gaming, and if gaming under a VM is sufficient I'd be happy to do that.

You can game in a VM...using the pass through feature to dedicate a video card to the Windows guest. It's a fair amount of effort to set up though and still not perfect. Xen can do it (and Linux KVM too). I think Virtualbox may have support now too under Linux.

BTW, most Asus AM3+ boards (maybe all?) have support the virtualization features and ECC (unbuffered) memory.