Awful FreeBSD 9 block IO performance in KVM

[Richard Yao]

On 07/20/2012 03:44 PM, Adrian Chadd wrote:
> On 19 July 2012 11:27, Richard Yao <ryao at gentoo.org> wrote:
>> Dear Everyone,
>>
>> FreeBSD 9 has awful block IO performance in KVM. I have experienced it
>> and others have experienced it. Someone posted slides to slideshare with
>> benchmarks documenting it:
>>
>> http://www.slideshare.net/TakeshiHasegawa1/runningfreebsdonlinuxkvm
>>
>> Slides 13 and 20 are particular eye openers. Does anyone know what is wrong?
> 
> For those watching at home - this is bad performance _with_ the virtio
> drivers themselves, not just with SCSI emulation.
> 
> Slide 17 is very telling - the operation latency is quite high.
> 
> Richard, are you able to easily test out things on FreeBSD-HEAD guest
> in a Linux KVM? If so, some of the storage/block/GEOM driver people
> may be able to step up and start offering some ideas.
> 
> Thanks,
> 
> 
> 
> Adrian

Dear Adrian,

I am in the process of setting up a VM instance specifically for this.
While installing it, I noticed that qemu-kvm printed 'lsi_scsi: error:
ORDERED queue not implemented', which might be a clue as to why the
block device performance is bad.

Also, I will try testing raw disk IO for Ivan after I have it setup.

Yours truly,
Richard Yao

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