[vfio-users] Looking for performance tips, qemu machine type and pci/pcie-root questionning?

Will Marler will at wmarler.com
Tue Apr 19 21:08:54 UTC 2016

I'm glad you shared your process & experience, good job getting it working,
and interesting 3dmark benchmark. How do you feel about game performance?
I'm guessing 3% isn't noticeable.


On Tue, Apr 19, 2016 at 3:01 PM, thibaut noah <thibaut.noah at gmail.com>

> So, i switch my vm container to bare metal in order to do some bench with
> native windows install.
> Seems the difference between vm and native in 3dmark firestrike is about
> 3%, just so you know.
> 2016-04-15 8:17 GMT+02:00 Blank Field <ihatethisfield at gmail.com>:
>> On Apr 15, 2016 9:01 AM, "thibaut noah" <thibaut.noah at gmail.com> wrote:
>> > Speaking of drives, it seems from what i read that it is possible for
>> qemu/kvm to read a native (non virtualize) install of windows from a
>> passthrough drive.
>> > If so is there something special to do? Might go to the hassle of
>> reinstalling my all windows system by i prefer to be sure before touching
>> anything (though i might just backup the image, boot my vm from it and
>> clone windows, much easier than reinstalling).
>> There is a problem, that i've promised to git bisect, but trashed my
>> fedora instead.
>> The thing is, you give the whole drive (or just the necessary partitions)
>> to the vm, and you can either boot the OS inside a VM, or run it bare-metal.
>> There are some culprits, for example:
>> If using UEFI, in order to properly mirror the install, you have to copy
>> the efivars. Windows relies on them to activate itself.
>> If using not virtio-scsi, you don't send the scsi commands. The most
>> noteworthy are SMART and TRIM.
>> And the final one, since some version of OVMF, GPT formatted drive gets
>> checked for valid MBR and it fails to boot.
>> But the performance is closest i could get to native, my HDD gets around
>> 150-180MBps, just as it does baremetal.
>> Not sure about IOPS though.
>> This kind of setup is useful for AB testing.
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