Disk write/read speed degration when configuring PCI passthrough on PVE4.0

[Hiroki Wakabayashi]

Hello Experts,

Just upgraded PVE 3.4 to 4.0 few days ago.
One of my guest VM machine is using PCIe passthrough, and it was okay when on PVE 3.4.
Right after upgraded to 4.0, I am experiencing severe Disk RW speed degrades..
I had followed procedure on wiki in order to configure PCIe passthrough on PVE4.0.

Disk write speed decreased to 3-7MB/s, when configuring PCIe passthrough.
IF I remove PCIe passthrough setting, Disk write speed is nearly around 500MB/s.

My guest VM is Centos6.7, and using default kernel image provided on Centos (2.6.32)
Has anyone see this issue?

Thanks,
Hiroki

 

[wolfgang]

Hi,
How do you passthrough the disk or do you paasthrough the entire controller?

 

[Hiroki Wakabayashi]

Hi,
Thanks for your quick response.

I am passing through PCIe digital TV card, and not the disk nor disk controller.
Issue I am facing is somehow virtual SATA/SCSI disk on Guest VM drops off speed dramatically by configuring PCIe passthrough on guest VM. (around 3-7MB/s)
If I omit configuring PCIe passthrough, Disk speed goes back to normal speed.

---pci information on host---
# lspci -v | grep -A 10 07:00
07:00.0 Multimedia controller: Altera Corporation Device 4c15 (rev 01) <<-- this is my TV card I am willing to passthrough
Subsystem: Device ee8d:0368
Flags: fast devsel, IRQ 18
Memory at 383ff2101000 (64-bit, prefetchable) [disabled] [size=4K]
Memory at 383ff2100000 (64-bit, prefetchable) [disabled] [size=4K]
Capabilities: [50] MSI: Enable- Count=1/1 Maskable- 64bit+
Capabilities: [78] Power Management version 3
Capabilities: [80] Express Endpoint, MSI 01
Capabilities: [100] Virtual Channel
Kernel driver in use: vfio-pci

--config for VM guest
boot: cn
bootdisk: virtio0
cores: 4
hostpci0: 07:00.0,pcie=1,driver=vfio <<<<<<< PCIe passthrough setting based on Wiki
machine: q35
memory: 16384
--snip--
ostype: l26
scsihw: virtio-scsi-pci
--snip--
virtio0: raid5array:100/vm-100-disk-1.qcow2,format=qcow2,cache=writeback,iothread=on,size=2000G


Thanks,
Hiroki

Hi,
How do you passthrough the disk or do you paasthrough the entire controller?