KVM performance issues

[syadnom]

v5.1-41

as a cheap benchmark, I'm compiling asterisk on centos7
kvm cpu type = host, numa=on
specs for KVM and LXC vm/container same

In VM, this takes 25 Minutes,
in LXC, this takes 7 Minutes.

Any idea where to start to identify this performance gap?

I'm actually running asterisk on centos7/kvm in production on this box and I'm having performance issues that seem to be this KVM performance problem.

Thanks.

 

[Rares]

Did you configure the VirtIO drivers in KVM? In my case I got a double R/W disk speed improvement.

https://pve.proxmox.com/wiki/Windows_VirtIO_Drivers

 

[syadnom]

No, but I found something peculiar.

running `sysbench --test=memory run`

in LXC I get 277.65MB/s
in KVM I get 41.10MB/s

I did the same tests with CPU and they are nearly identical.

Is there something in KVM that would be limiting memory rates?

 

[NewDude]

As a data point: on a Dell T30 pve I've got a mostly idle kvm web server that I just installed sysbench on.

It gave me the following:



Nothing fancy on that server at all, also running Centos 7.

 

[ssaki]

No, but I found something peculiar.

running `sysbench --test=memory run`

in LXC I get 277.65MB/s
in KVM I get 41.10MB/s

I did the same tests with CPU and they are nearly identical.

Is there something in KVM that would be limiting memory rates?

Just to note that even your LXC result looks very slow, most modern SSDs will give you double that in sequential reads.
On a Xeon 5600/DDR3 I'm getting ~2400 MB/s on the host and ~2100 MB/s inside a KVM guest (pve 4.3) and that's already aging platform.

Your CPU may lack some of the hardware virtualization features necessary. If the CPU is not that old then double check the BIOS and ensure that there is no option to disable hardware virtualization that is turned on

 

[syadnom]

yeah, I'm seeing that. one of my other prox hosts gives 3465MB/s in KVM and 3922MB/s on the host. I'm only getting 267MB/s on LXC and the Host here, I think my LXC results before were not accurate. ECC Ram in this server so I suspect I have a bad chip and ECC is masking that with slow performance. Thanks for the numbers.