bhyve performance problem with SQL server

Allan Jude allanjude at
Sun Oct 7 18:46:57 UTC 2018

On 2018-10-07 11:31, Andrea Venturoli wrote:
> Hello.
> I've got a FreeBSD 11.2 box running vm-bhyve with two Windows virtual
> machines, each with an instance of MS SQL server.
> Everything works fine normally, but there's a specific operation which
> will impose an high CPU load on the machine and last several minutes,
> when it's expected to get the results in a few seconds.
> I think I have to pass this trouble to the "programming" people, but
> before I do that, I'd like to double-check this is not a system problem.
> Some notes:
> _ that specific operation will put the two VMs in touch with each other,
> as one will contact the DBMS on the other and import data; however,
> that's not the only procedure which does such a thing and the others are
> working fine;
> _ during the execution of such procedure, the load on the host rises, as
> both VMs show high CPU usage (in Task Manager), top shows both bhyve
> processes in kqread (but this happens all the time), disk activity
> doesn't seem so high;
> _ the box has a Quad-Core CPU and I assigned two cores to each VM (I
> have hw.vmm.topology.cores_per_package=4 in /boot/loader.conf);
> _ both VMs use virtio-net, with both tap interfaces connected to the
> same "virtual switch";
> _ both VMs use a zvol for their HD.
> Before I sentence this is an application level problem, is there some
> improvment I could do to the above? Any check or test I should run?
>  bye & Thanks
>     av.
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What is the 'volblocksize' of your zvol? What block size are you using
for the bhyve virtual device? is it virtio-blk or ahci?

Can you tell if the problem is related to disk IO?

Allan Jude

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