iothread option not working?

[Waschbüsch]

Hi all, I just tried to enable the 'iothread' flag for a disk on a test VM:

The disk is configured like this (from /etc/pve/qemu-server/100.conf):
scsi0: disks:vm-100-disk-1,cache=writeback,discard=on,size=4G

The scsi-backend is virtio.

The popup allows me to select the checkbox, but clicking 'OK' does not change the hard disk config. (Neither does it give me an error).

My thoughts are that some requirement to enabling the option is not met (in which case it should not be selectable?)

Can someone let me know under which circumstances I can enable the option?

Thanks,

Martin

 

[dietmar]

That option only works with virtio drives (But yes, it should not be selectable)

 

[Waschbüsch]

Thanks for clearing that up, Dietmar!

 

[dietmar]

I opened a bug here: https://bugzilla.proxmox.com/show_bug.cgi?id=973

 

[vkhera]

Does it also depend on the storage being local or does it work for network storage as well?

 

[dietmar]

Does it also depend on the storage being local

AFAIK this does not matter.

 

[spirit]

It's also working with virtio-scsi (using virtio-scsi-single controller)

 

[mir]

Someone made some performance test with or without iothreads (virtio and virtio-scsi)?

 

[spirit]

Someone made some performance test with or without iothreads (virtio and virtio-scsi)?

I have made benchmark with ceph/rbd, which is cpu intensive.

with virtio+ iothread : 1 iothread - 1 disk: 70000 iops
2 iothread - 2 disk: 140000 iops
4 iothread - 4 disk: 380000 iops


with virtio without iothread : 1 disk: 70000 iops
2 disk: 70000 iops
4 disk: 70000 iops

with other storage (iscsi/nfs), I think you can already do more iops without iothread.


The plan for qemu 2.7/2.8 , is to be able to use multiple iothread for 1 disk.

 

[vkhera]

It's also working with virtio-scsi (using virtio-scsi-single controller)

I am unable to make the checkbox "stick" like the OP, even with a virtio-scsi device. The disk is stored on a gluster FS, which is why I asked about network based vs. local.