How does multiqueue really work?

mgiammarco

Active Member
Feb 18, 2010
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Hello,
I would like to add multiqueue support.
I read:
- number of queues must be the same of number of cpus: false, in proxmox I can put 8 multiqueues and not more
- in linux vm I must give the command ethtool -L ens1 combined X.... but unfortunately I am using windows VM

Can someone explain me the truth?
Thanks,
Mario
 

spirit

Famous Member
Apr 2, 2010
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multiqueue is for splitting rx packets (incoming), to different queues/cpu in the vm.
I'm not sure about the 8 queue limit, maybe it's a proxmox gui limit. (can you try to change the value in vm config file directly ?).
But I think it could be increase.

It's only usefull if you receive a lot of small packets (like a synflood ddos for example). 1 queue is able to reach around 250-500 kpps. (Then you should see 1 core saturated)

I last linux kernels (> 4.15 If I remember correctly), you don't need to use ethtool anymore, the driver is able to setup queue correctly from value defined at proxmox side.

For windows, I don't remember it need special tuning. (if it need tuning, it should be in the nic options )
 

mgiammarco

Active Member
Feb 18, 2010
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Thanks for reply, I have checked in nic options and there is nothing specific to multiqueue.
 

mgiammarco

Active Member
Feb 18, 2010
93
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28
I would like to underline that proxmox official documentation says that you must put mulitqueue=number of threads BUT then proxmox gui behaviour is different from official documentation
 

mgiammarco

Active Member
Feb 18, 2010
93
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28
Anyway I have tried enabling multiqueue=8 in some test windows VM and freenas VM and I obtained total damage: network up and down, packet loss and so on
 

spirit

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Apr 2, 2010
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I also tried to config mulltiqueue but maximum limit at 8. How i config more?
I think it's a limitation of the gui only.

you can try to edit the vm config file in /etc/pve/qemu-server/<vmid>.conf, and increase the queue=.. value on the netX: interface.

you should be able to use as maximum the total number of cores of your vms.
 
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t.natakorn

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Nov 22, 2019
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I think it's a limitation of the gui only.

you can try to edit the vm config file in /etc/pve/qemu-server/<vmid>.conf, and increase the queue=.. value on the netX: interface.

you should be able to use as maximum the total number of cores of your vms.

Thank you, now it can reach my total no of cores.
 

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