GPU Passthrough Recommened CPU

Software & Operating Systems Linux
1

What should I buy?

Title basically says it all. I have been chasing the GPU passthrough dream for about a year. I have been dissapointed with the performance I have had with my current build and am trying to find out if different/more hardware would solve my issues. So, to give some back-story I will tell you my journey thus far.

Initially/Currently I had/have it set up as follows:

PC Specs

GPUS

Nvidia 970 Host - KDE Neon
Sapphire Fury Guest - Windows 10

CPU

Xeon E3 1230 V5

Mobo

ASUS E3 Pro V5

This setup worked, sort of. However, while I was getting very good fps, I was getting micro-stuttering every 5/10 seconds. The fps wouldnā€™t drop according to the logs, but you could see a stutter and could hear ever so slight fan revving as well. This made it quite unenjoyable to game with. I tried multiple distros to solve the problems, I tried WINE and all the normalish things to try and solve the problem, but no real luck. I came to two conclusions which I have no real way of testing because I donā€™t have a plethora of hardware to test with.

A) The ASUS E3 Pro V5 does not support 16x sli/crossfire. When in dual GPU mode the 2nd slot defaults to 4x. I wonder if I was having some kind of bottlenecking here.

B) The Xeon is only a 4 core 8 Hyperthread CPU. When passing 6 threads to the VM it ran much better than with 4 threads, but not perfect, especially in MMO games (specifically GW2) where CPU speed was critical. GW2 was basically unplayable even with 6 threads and a Fury GPU, which seems insane.

Fast forward to today. I have kind of given up on the passthrough. I sold my 2nd gpu and my fury and purchased a 1080. I only run Windows on the machine and only play games on that computer. I use my laptop (an old Lenovo y510p) for linux and use a KVM switch to switch between the machines. This is okay, but I really want to use my desktop horsepower on Linux as I do a fair bit of video editing for my work situations.

So, with that all in mind (I hope someone reads this far, sorry for the life story.) what CPU would you recommend? I have settled with AMD because I really believe that my issue was needing more cpu cores and dual x16 pcie slots. Should I go with a Ryzen 1700/1700x or go whole hog with a TR4 build with a 1920x or 1950x(is that overkill?).

Any and all advice is appreciated. I am currently running Fedora 27 on my laptop, but Iā€™m open to other distros as well. (Also the ā€œduelā€ booting option sounds interesting.)

Thanks in advance,

Uziah

2

So, the X299 Intel platform is as close to ā€œperfectā€ as we can expect at the moment for passthrough. The major barrier to entry there is definitely going to be the price. Itā€™s not cheap.

Iā€™m not sure what sort of budget youā€™re looking at, but if you have the money, X299 is your go-to.

Ryzen isnā€™t a bad second choice. Youā€™ll want to watch the Level1Linux videos on Ryzen passthrough to understand the quirks with it though.

Also, keep in mind that now is an exciting time for passthrough because a lot of things are happening to make passthrough less complicated and more user friendly.

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3

You could go X79 if you could find the motherboards for cheap. Server/workstation surplus with dual socket 2011 Xeons could work too. Iā€™m working with X79 at the moment and the platform itself is currently perfect for passthrough. Only issue you may have depends on the USB 3.0 controller cards on the motherboards themselves. Fresco Logic has a reset issue like RX Vega, so the system has to be fully shut down before it will work again. VIA Controllers are no dice when IOMMU is turned on. They just simply stop working when the grub switch for IOMMU is turned on.

Best part about this: X79 had no arbitrary PCI lane segmentation across the product line. That only started with X99. You get a full 40 lanes worth of bandwith to the CPU, albeit only PCI-E 2.0, but that makes Blackmagic cards play nicer.

4

Thank you both for your great advice.

I donā€™t think I want to go x79. I live in Australia, so finding cheap used stuff is a lot harder than in the USA. Also, it feels like a step forward in one way but backward in others.

If threadripper is miles ahead of Ryzen 7, I will save for it. I was just kinda wondering if it was more power than I really needed. Just after my experience with the quad core Xeon, I am feeling a bit burned by the process and want to make sure that my next purchase has the overhead to really do what I want and expect it to.

Just re-reading your post @SgtAwesomesauce, X299 not X399? So intel being the way to go and not AMD? That kinda makes me sad :stuck_out_tongue:

5

Threadripper is broken-ish for passthrough, iirc with Vega its doable. I could not get it to work with nvidia cards for the guest when I tried in september.
Check wendells videos on the subject. X299 does work good, albeit very expensive.
AM4 works with some quirks (npt bug is fixed so compile a new kernel, and some smt things with qemu iirc) check the /r/vfio and/or their discord for specific motherboards.

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6

Well, if talking about threadripper, that is also quite pricey, so cost isnā€™t the main factor. I thought x299 had a whole host of other problems with disabling this and that (I donā€™t know, I only really saw Linusā€™ rant on one of his videos about it.) I will definitely look for Wendellā€™s video and check those redit threads. Thank you!

7

Threadripper would probably be excellent when its fixed, 60 pcie lanes - nvme not stuck on the dmi etc

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8

Yeah, if it is ā€œgoing to beā€ fixed in under a year I feel like Iā€™d get more use out of it in the long-term. It is a similar price here for the TR 1950x and the i9 7900x. So, 16 cores, vs 10. I feel like 10 is probably enough but 6 extra seemsā€¦cool. Lol!

9

Okay, so used equipment is not possible. In that case, Iā€™d wait for Threadripper to be sorted. The PCI-E errors has to be related to the microcode so wait for the AGESA update that fixes Threadripper.

10

Thought Iā€™d post a brief recap to where I am with things, sort of a TL;DR version -

I started off building a 1950X / Gigabyte X399 Aorus 7 system - it let me validate some aspects of TR, enough so that it gave me some confidence to go ā€˜all outā€™ on building a second box, with the Asus Zenith Extreme.

My goal was to have the Zenith box as a desktop and use the ā€œotherā€ 1950X system as my virtualisation server - however, I started to run into some issues - mainly painpoints by not being on Intel. Given that ECC wasnā€™t a major concern, Iā€™ve since returned the 1950X CPU back to Amazon for a full refund of $879.99 - especially when Amazon is NOW reselling the same CPU for 799.99 (haha!).

During the same time, I ended up ordering a second Zenith Extreme board, which Amazon will let me hang onto till 1st Feb 2018; so if I want to return it, Iā€™ll have to do it thenā€¦ BUT instead, Iā€™ve decided to keep the mobo towards TR once all these issues are sorted or Threadripper 2. Who knows, I may be able to snag a 1950X for $750 in January? That wouldnā€™t be too bad.

TL;DR I now have an i9-7920X on the way for $1,099/- (Amazon) and a Strix X299 mobo. Will pickup a Vega 64 and have a play with GPU pass through then :wink:

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11

For ease of use, Intel is the way to go. AMD requires a bit more work and the patches for native performance are not currently available. Iā€™m just going off Wendellā€™s recommendation that Intel is the best ā€œplug and playā€ solution, but AMD will require a bit of work.

I wholeheartedly support AMD and would love for people to use it. Iā€™m actually currently building an R7 system for this purpose exactly. Iā€™m just not really happy with the software support for AMD at the moment. That said, it should change with 4.16 release.

On a side note: Whoever at AMD decided to pre-empt Intel on their naming scheme should be fired. It was a good meme, but aside from that, itā€™s completely unprofessional and annoying.

Ryzen 7 is mature now, Iā€™d say that TR is going to take a bit longer to mature because of the smaller user base.

@bsodmike has a lot of experience in the field. If youā€™ve got questions about TR, heā€™s your guy.

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12

Ty for that insight @bsodmike. So threadripper isnā€™t quite there for this scenario, whereas x299 is dead easy. I will definitely keep that in mind. Thank you!

Okay, so if you @SgtAwesomesauce are making an R7 build, that would suggest to me that 8 cores and 16 threads is plenty for gpu passthrough without any bottlenecks to the windows vm. Would that be correct? Because that would lower the barrier to entry quite significantly and let me buy more cooling/storage/ram.

Remember, for me the only thing windows vm will do is play games like PUBG, WoW, GW2, CS:Go, etc. The linux host is where I will be doing my video editing etc.

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14

It really depends on your use case. If games will be your most resource intensive operation, 8/16 is plenty for almost all games.

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@SgtAwesomesauce, yes. Games are the ONLY thing the windows vm will do. All video editing, photo editing, rendering, etc will be done under linux.

16

In that case, youā€™ll be very happy with an R7 build.

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17

Thank you very much. you just saved me 1.5k dollars :wink:

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18

Can you send some of that my way? ā€œfinders feeā€ :smiley:

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19

sorry, your message is breaking upā€¦((##&!@&!..tunnel@#()(@(ā€¦canā€™tā€¦hearā€¦youā€¦

dial tone endsā€¦

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20

typicalā€¦ LOL.

21

If you know, were your issues with nVidia something thatā€™s been fixed with patches, or is it still the case that GPU passthrough requires Vega? And is this limited to threadripper? Iā€™m curious as I was thinking about building a 1950X with KVM passing through an nVidia 1070/1080.