[Qemu-devel] Enabling vhost-net cause insane high memory usage.

[Qemu-devel] Enabling vhost-net cause insane high memory usage.

[Piotr Karbowski]

Hello,

kernel 3.12.5, qemu-1.7.0.

With vhost=on, qemu shortly after start uses all its assigned memory (2G 
for example), without vhost-net enabled it does not go to more than 200 
MB on my idling test virtual machine. 100% reproducable. I think its not 
how it should be.

Full command:
/usr/bin/qemu-system-x86_64 -machine accel=kvm -name _debian -usb 
-machine accel=kvm -cpu host,level=9 -smp cpus=2 -vga std -monitor 
unix://home/piotr/src/vmninja/sockets/_debian.monitor.socket,server,nowait 
-vnc unix://home/piotr/src/vmninja/sockets/_debian.vnc.socket -m 2048 
-boot order=d,menu=on -drive if=ide,index=2,media=cdrom,id=virtcd 
-netdev tap,id=if0,helper=/usr/libexec/qemu-bridge-helper --br=lebridge0 
-device virtio-net-pci,netdev=if0,mac=de:ee:b3:9e:a3:d5,romfile= -drive 
file=/home/piotr/virt/kvm/_debian.raw,if=virtio,cache=writeback

-- Piotr.

Re: [Qemu-devel] Enabling vhost-net cause insane high memory usage.

[Stefan Hajnoczi]

On Fri, Jan 10, 2014 at 12:00:31AM +0100, Piotr Karbowski wrote:
> kernel 3.12.5, qemu-1.7.0.
> 
> With vhost=on, qemu shortly after start uses all its assigned memory
> (2G for example), without vhost-net enabled it does not go to more
> than 200 MB on my idling test virtual machine. 100% reproducable. I
> think its not how it should be.
> 
> Full command:
> /usr/bin/qemu-system-x86_64 -machine accel=kvm -name _debian -usb
> -machine accel=kvm -cpu host,level=9 -smp cpus=2 -vga std -monitor unix://home/piotr/src/vmninja/sockets/_debian.monitor.socket,server,nowait
> -vnc unix://home/piotr/src/vmninja/sockets/_debian.vnc.socket -m
> 2048 -boot order=d,menu=on -drive
> if=ide,index=2,media=cdrom,id=virtcd -netdev
> tap,id=if0,helper=/usr/libexec/qemu-bridge-helper --br=lebridge0
> -device virtio-net-pci,netdev=if0,mac=de:ee:b3:9e:a3:d5,romfile=
> -drive
> file=/home/piotr/virt/kvm/_debian.raw,if=virtio,cache=writeback

How are you measuring memory usage?  Please post the output of the
command.

Did previous kernel/qemu versions work better?

Maybe Michael or Jason can give you hints on debugging this.

Stefan

Re: [Qemu-devel] Enabling vhost-net cause insane high memory usage.

[Michael S. Tsirkin]

On Fri, Jan 10, 2014 at 12:00:31AM +0100, Piotr Karbowski wrote:
> Hello,
> 
> kernel 3.12.5, qemu-1.7.0.
> 
> With vhost=on, qemu shortly after start uses all its assigned memory
> (2G for example), without vhost-net enabled it does not go to more
> than 200 MB on my idling test virtual machine.

Could you explain how you measure that exactly?

> 100% reproducable. I
> think its not how it should be.
> 
> Full command:
> /usr/bin/qemu-system-x86_64 -machine accel=kvm -name _debian -usb
> -machine accel=kvm -cpu host,level=9 -smp cpus=2 -vga std -monitor unix://home/piotr/src/vmninja/sockets/_debian.monitor.socket,server,nowait
> -vnc unix://home/piotr/src/vmninja/sockets/_debian.vnc.socket -m
> 2048 -boot order=d,menu=on -drive
> if=ide,index=2,media=cdrom,id=virtcd -netdev
> tap,id=if0,helper=/usr/libexec/qemu-bridge-helper --br=lebridge0
> -device virtio-net-pci,netdev=if0,mac=de:ee:b3:9e:a3:d5,romfile=
> -drive
> file=/home/piotr/virt/kvm/_debian.raw,if=virtio,cache=writeback
> 
> -- Piotr.

Yes, this should not happen.
One interesting thing to try would be switching device type from
virtio-net to e1000.

This means vhost will be initialized but not started.

-- 
MST

Re: [Qemu-devel] Enabling vhost-net cause insane high memory usage.

[Piotr Karbowski]

Hello,

On 01/15/2014 11:03 AM, Michael S. Tsirkin wrote:
>
> Could you explain how you measure that exactly?
>

I check the resident memory (RES) of qemu-system-x86_64 proces.


> Yes, this should not happen.
> One interesting thing to try would be switching device type from
> virtio-net to e1000.
>
> This means vhost will be initialized but not started.
>

So with virtio-net-pci + vhost=on I have VM process on 580-590 MB of RES 
memory, if I disable vhost OR set e1000 NIC and leave vhost enabled, its 
take just 109-120 MB of resident memory.

The memory usage check is done after few minutes after VM start, and the 
vm have minimal debian7 system without even single additional service.

-- Piotr.

Re: [Qemu-devel] Enabling vhost-net cause insane high memory usage.

[Piotr Karbowski]

On 01/15/2014 10:36 PM, Piotr Karbowski wrote:
> Hello,
>
> On 01/15/2014 11:03 AM, Michael S. Tsirkin wrote:
>>
>> Could you explain how you measure that exactly?
>>
>
> I check the resident memory (RES) of qemu-system-x86_64 proces.
>
>
>> Yes, this should not happen.
>> One interesting thing to try would be switching device type from
>> virtio-net to e1000.
>>
>> This means vhost will be initialized but not started.
>>
>
> So with virtio-net-pci + vhost=on I have VM process on 580-590 MB of RES
> memory, if I disable vhost OR set e1000 NIC and leave vhost enabled, its
> take just 109-120 MB of resident memory.
>
> The memory usage check is done after few minutes after VM start, and the
> vm have minimal debian7 system without even single additional service.

Quick note, the test was done on VM with 512 MB memory set, if I test it 
on the 2 GB one, RES with vhost-enabled virtio-net-pci goes a bit above 
2 GB shortly after start.

-- Piotr.