Kvm poor cpu performance

Kvm poor cpu performance

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It only takes a minute to sign up. I use Ubuntu I run Windows 7 in KVM and it's extremely slow. My co-worker use Debian on the same PC configuration and can run Windows 7 extremely fast!

Where can be my problem? I've successfully installed VirtIO drivers, and it gave me a few of performance, but, for example, when I open Firefox in Windows, even mouse moves very slowly, and GUI is very slow too. Try changing it to a SATA bus. Better yet, install the virtio drivers in Windows 7, and change it to a virtio bus.

One other thing worth checking is: is your co-worker using a disk-image for the VM, same as you are, or are they using a raw disk partition or an LVM volume or similar? I also had incredibly slow performance with my virtual HDD. The following setting on new HDD corrected everything:. To anyone who installed on IDE and now wishes to switch to virtIO: A convenient way to do it is to create a secondary non-boot virtIO disk, boot the VM -- at which point Windows will ask for the virtIO drivers, which it somehow refuses to install otherwise -- and subsequently switch the boot partition to virtIO.

HDD configuration like Sergey said. When creating the VM with virt-manager, don't create the disk immediately unclick "enable storage You should install VirtIO drivers under Windows. You can download drivers built by Fedora or build your own from source, see the KVM documentation for information. Sign up to join this community. The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered.

Asked 7 years, 7 months ago. Active 5 years, 3 months ago. Viewed 79k times.

KVM Performance Limits for virtual CPU cores

Changes to this xml configuration should be made using: virsh edit windows or other application using the libvirt API. Braiam Guy Fawkes Guy Fawkes 1 1 gold badge 2 2 silver badges 10 10 bronze badges.

Thx - the - Storage format: raw - Cache mode: none not default! Normally I'd expect a performance gain from writeback caching?

What is the name of this application? Active Oldest Votes. Similarly, you will get improved network performance if you change the NIC type to virtio. What version of KVM and kernel are you running on ubuntu? And what version of same on debian? Can you describe how to install VirtIO drivers? IIRC it was something clumsy like mount the CD image and hunt for the installer program in one of the subdirectories and click on it.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

The dark mode beta is finally here. Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. When using a LXC guest as router, everything is fine.

I get Mbits max. This has been so since over a year now, since I started using KVM. If I do not solve this problem, I will have to dump libvirt because such performance is unacceptable. It is pretty hard to diagnose these sort of problems with such limited information. Definitely don't use e or any other NIC model - virtio-net will offer the best performance of any virtualized NIC. If you want to use a guest as a high performance network routing appliance though, there's quite a few ways to tune it the VM in general.

Pinning the guest vCPUs to specific host physical CPUs, and keeping other guests off these CPUs ensures the guest won't get its cache trashed by being pre-empted by other processes. Learn more. Asked 3 years, 3 months ago.

Active 3 years, 3 months ago. Viewed times. I have an Arch Linux host which runs virtualised router. Hardware polling is disabled. Stack Overflow is a site for programming and development questions.

This question appears to be off-topic because it is not about programming or development. See What topics can I ask about here in the Help Center. Also see Where do I post questions about Dev Ops? I see. Thank you for pointers.

It looks like it's more of a libvirt problem than pfSense problem, because I have another VM with Arch linux in it which runs hostapd AP, and it exhibits the same problem. Active Oldest Votes. DanielB DanielB 1, 6 6 silver badges 10 10 bronze badges. Thanks for the ideas. I read somewhere that this is optimal for AMD Kabini host.

The rest of what you wrote goes a bit over my head, I'm afraid. But from what you wrote I gather, those are secondary potential offenders. Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password. Post as a guest Name.

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kvm poor cpu performance

Featured on Meta. Community and Moderator guidelines for escalating issues via new responseā€¦.I spent the last two days trying and troubleshooting but it seems like I cannot get to the bottom of this one. On boot no signal is coming from the which is expected, I can see the Unraid boot sequence plugging the mobo VGA output into the monitor.

The VM boots and there is output to the display from the but the performance is shockingly slow. The VM is laggy and choppy and opening task manager it looks like the GPU is over-utilised even in idle?!? It also seems like the PhysX feature is missing when virtualised compared to bare metal.

GPU works as expected and I get normal behaviour and performance. Same problem as described above when virtualised with very poor GPU performance, even just moving a window on the desktop looks slow and laggy.

Am I missing something so silly that I am over-complicating my troubleshooting? I tried some search and could not find anyone with a similar problem that was not related to poor array performance in my case no problem here, vdisks are on the cache SSD and I also tried with an unassigned drive passed through to the VM. It looks like Windows is not interfacing directly with the GPU even though it should and there is some bottleneck somewhere in the virtualisation layer.

Windows Do you know what process is causing the GPU load? I ran a gtx ti on my VM for quite a while before selling it when I parted out my gaming rig and replacing it with my and didn't have problems like that. I had a for a while that did have issues with that just due to how weak of a card it was. The GPU tends to work if you get it passed through unless its overheating and throttling although your GPU-Z screen shows its running pretty normally. Also, you said you changed the power settings for the GPU in the nvidia control panel.

Did you change the power plan to High Performance for windows too? Anyways, I hope you get some more suggestions from other users and you can figure out this issue.

Thanks for your reply, as per my previous post, the two processes I can see smashing the GPU even though it doesn't look like running at its best anyway are System and Desktop Window Manager and I can see both running as 3D and Copy. I had high performance set in Windows on the old VM, haven't tried with the new one I created, I'll give it a go.

Should I also try an older driver for the GPU just in case? It's like it's passing a lot of load on the GPU. When in the VM, 3DMark doesn't even load the test and hangs while loading system info. Edit: I updated Unraid to 6. Here is the link to the. Strangely enough, updating to 6. I'd say 6. I also followed all your suggestions, applied the msi fix and changed few settings here and there to optimize the VM.

You can post now and register later. If you have an account, sign in now to post with your account. Note: Your post will require moderator approval before it will be visible.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service. Ask Ubuntu is a question and answer site for Ubuntu users and developers. It only takes a minute to sign up.

However, if the CPUs are overallocated, then performance will suffer. Ubuntu Community Ask! Sign up to join this community. The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered. Asked 3 years, 4 months ago. Active 3 years, 1 month ago. Viewed 1k times. Thank you. Active Oldest Votes. JohnP JohnP 5 5 silver badges 5 5 bronze badges.

6 Gamers, 1 GPU? VMWare Makes It Possible!

Like latency etc. If you don't over-commit RAM, it is a non-issue. Sign up or log in Sign up using Google. Sign up using Facebook.

kvm poor cpu performance

Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. The Overflow How many jobs can be done at home? Featured on Meta. Community and Moderator guidelines for escalating issues via new responseā€¦. Feedback on Q2 Community Roadmap. Related 4. Hot Network Questions.Open-Source Routing and Network Simulation. I need to determine the maximum number of KVM virtual machines that can run on an average laptop computer.

Unfortunately, I cannot find authoritative information about the maximum number of KVM virtual machines that can run on a host computer. Most information I could find about KVM limits does not publish absolute limits but, instead, recommends best practices. In this post, I will synthesize the information available from multiple sources into a single recommendation for the maximum number of KVM-based nodes that can run in an open-source network simulator running on a single host computer.

KVM allows the user to set the number of virtual cores used by each virtual machine. The best practices for virtual cores on each virtual machine are:. Most laptop and desktop PC processors offer hardware support for virtualization. But there is a limit to how many virtual machines can run using hardware support. Hardware support varies depending on the processor; some processors provide better performance than others.

As a best-practice guideline, when using normal consumer-grade computers or laptops, you should assume hardware support for KVM virtualization is limited to 8 virtual cores for each real processor core on the host computer. For example, a dual-core laptop computer can support 16 virtual machines or 8 virtual machines with 2 virtual cores, each. However, this assumes that not all guests use all their allocated memory at the same time.

If you run applications that use up all this memory on every virtual machine when overbooking memory, expect poor performance.

Good information about other KVM limitations for memory, network interfaces, and other resources are described at the Fedora project and the OpenSUSE project web sites. See the comments posted below by a Red Hat developer who disagrees with this description. How exactly did you reach that conclusion? Thanks for your comment. When experimenting with the Cloonix network emulator, which uses KVM, I noticed a significant increase in the time it took for nodes to initialize after I had more than 16 VMs starting.

When looking for some sort of authoritative information about how many KVM VMs I could run at the same time, I found the links to which I refer in this post. So, based on my observations and the information available to me, I created my conclusion. I would be happy to look at any documentation that would shed a brighter light on this issue.Hey guys, long time lurker here and i've finally given up and need your help.

I have very poor VM performance with win 10 I have also tried win8 and ubuntu, both no good. I have been searching around the forums and haven't found a solution that works. Fullscreen video in chrome is extremely laggy. In games I am usually around fps with very low settings.

One thing I did to try and narrow it down was I disabled cool n quiet in bios to keep the cpu at 4ghz, but it didn't change the performance at all. I am thinking GPU? Any thoughts?

I'd recommend trying the 6. AMD FX is the problem, atleast i think The OP has almost the same hardware config as you. It seems unraid, libtvirt, vfio, kvm, qemu doesnt like the amd fx series. Its not that i dont believe you, but im a little skeptic.

Maby its just an bad config, but im going to try an intel based cpu with the same GPU to see if maby this causes the problem. Add virtual machines to the mix and "prefer" changes to "strongly recommend.

I don't think AMD tests nearly as much as Intel does when it comes to virtualization technology on consumer-class chipsets. Certainly not for their GPUs. I updated to the latest 6. Games now typically run around 50fps on medium settings. I'm just glad they are playable now, not a hardcore gamer but more of a weekend warrior, so I'm not too picky.

Thanks for your help. I dont think your amd cpu does hyperthreading and it is just 8 plain cores, so you dont have to worry about making sure the thread pairs are from the same cpu core. Now in your vm manager pin the cores you just isolated to the vm do not pin any additional cores. The only downside to doing this is the isocpu cores are not available to the host unraid. But for nas operations unraid is very efficient so 2 cores would be fine for it. Running dockers doing transcoding etc obviously will use more resources.

However you can pin these isolated cores to dockers aswell even though they have been isolated. If you do pin to a core to a docker aswell then make sure the docker isnt running when you are using the vm or else it will effect the vm performance.

You can post now and register later. If you have an account, sign in now to post with your account. Note: Your post will require moderator approval before it will be visible. Restore formatting. Only 75 emoji are allowed. Display as a link instead. Clear editor.Modern processors come with a wide variety of performance enhancing features such as streaming instructions sets sse and other performance-enhancing instructions.

These features vary from processor to processor. QEMU and KVM default to a compatible subset of cpu features, so that if you change your host processor, or perform a live migration, the guest will see its cpu features unchanged.

This is great for compatibility but comes at a performance cost. If all your hosts have these features, compatibility is retained:. To see the difference between the capabilities of the host CPU versus the guest, just compare the output of the following commands on each system:. For example, the default setting on a 64 bit host machine is "-cpu qemu64". This includes the following flags:. QEMU defaults to user-mode networking slirpwhich is available without prior setup and without administrative privileges on the host.

It is also unfortunately very slow. To get high performance networking, switch to a bridged setup via the -net tap command line switches. Again this card is compatible with most guests, but does not offer the best performance. If your guest supports it, switch to the virtio model:. QEMU supports a wide variety for storage formats and back-ends. Easiest to use are the raw and qcow2 formats, but for the best performance it is best to use a raw partition.

You can create either a logical volume or a partition and assign it to the guest:. QEMU also supports a wide variety of caching modes. If you're using raw volumes or partitions, it is best to avoid the cache completely, which reduces data copies and bus traffic:.

As with networking, QEMU supports several storage interfaces. The default, IDE, is highly supported by guests but may be slow, especially with disk arrays.

kvm poor cpu performance

If your guest supports it, use the virtio interface:. Don't use the linux filesystem btrfs on the host for the image files. It will result in low IO performance. The kvm guest may even freeze when high IO traffic is done on the guest. Create account Log in. Toggle navigation.

Discussion View source History. Jump to: navigationsearch. CPU Performance Modern processors come with a wide variety of performance enhancing features such as streaming instructions sets sse and other performance-enhancing instructions. To pass all available host processor features to the guest, use the command line switch qemu -cpu host if you wish to retain compatibility, you can expose selected features to your guest. This includes the following flags: fpu de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 syscall nx lm up pni hypervisor The host itself might support other flags like cx16, mmxext, and so on.

Networking QEMU defaults to user-mode networking slirpwhich is available without prior setup and without administrative privileges on the host. Storage QEMU supports a wide variety for storage formats and back-ends.


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