Re: NFS in bhyve VM mounted via bridge interface

From: Paul Procacci <>
Date: Mon, 31 Oct 2022 06:02:22 UTC
On Mon, Oct 31, 2022 at 12:00 AM John Doherty <> wrote:

> I have a machine running FreeBSD 12.3-RELEASE with a zpool that consists
> of 12 mirrored pairs of 14 TB disks.  I'll call this the "storage
> server." On that machine, I can write to ZFS file systems at around 950
> MB/s and read from them at around 1450 MB/s. I'm happy with that.
> I have another machine running Alma linux 8.6 that mounts file systems
> from the storage server via NFS over a 10 GbE network. On this machine,
> I can write to and read from an NFS file system at around 450 MB/s. I
> wish that this were better but it's OK.
> I created a bhyve VM on the storage server that also runs Alma linux
> 8.6. It has a vNIC that is bridged with the 10 GbE physical NIC and a
> tap interface:
> [root@ss3] # ifconfig vm-storage
> vm-storage: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0
> mtu 1500
>         ether 82:d3:46:17:4e:ee
>         id 00:00:00:00:00:00 priority 32768 hellotime 2 fwddelay 15
>         maxage 20 holdcnt 6 proto rstp maxaddr 2000 timeout 1200
>         root id 00:00:00:00:00:00 priority 32768 ifcost 0 port 0
>         member: tap1 flags=143<LEARNING,DISCOVER,AUTOEDGE,AUTOPTP>
>                 ifmaxaddr 0 port 10 priority 128 path cost 2000000
>         member: ixl0 flags=143<LEARNING,DISCOVER,AUTOEDGE,AUTOPTP>
>                 ifmaxaddr 0 port 5 priority 128 path cost 2000
>         groups: bridge vm-switch viid-ddece@
>         nd6 options=1<PERFORMNUD>
> I mount file systems from the storage server on this VM via NFS. I can
> write to those file systems at around 250 MB/s and read from them at
> around 280 MB/s. This surprised me a little: I thought that this might
> perform better than or at least as well as the physical 10 GbE network
> but find that it performs significantly worse.
> All my read and write tests here are stupidly simple, using dd to read
> from /dev/zero and write to a file or to read from a file and write to
> /dev/null.
> Is anyone else either surprised or unsurprised by these results?
> I have not yet tried passing a physical interface on the storage server
> through to the VM with PCI passthrough, but the machine does have
> another 10 GbE interface I could use for this. This stuff is all about
> 3,200 miles away from me so I need to get someone to plug a cable in for
> me. I'll be interested to see how that works out, though.
> Any comments much appreciated. Thanks.
I was getting geared up to help you with this and then this happened:

# dd if=17-04-27.mp4 of=/dev/null bs=4096
216616+1 records in
216616+1 records out
887263074 bytes transferred in 76.830892 secs (11548259 bytes/sec)

dd if=17-04-27.mp4 of=/dev/null bs=4096
216616+1 records in
216616+1 records out
887263074 bytes transferred in 7.430017 secs (119416016 bytes/sec)

I'm totally flabbergasted.  These results are consistent and not at all
what I expected to see.
I even ran the tests on the VM first and the host second.  Call me confused.

Anyways, that's a problem for me to figure out.

Back to your problem, I had something typed out concerning checking rxsum's
and txsum's are turned off on
the interfaces, or at least see if that makes a difference, trying to use a
disk type of nvme, and trying ng_bridge
w/ netgraph interfaces but now I'm concluding my house is made of glass --
Hah! -- so until I get my house in
order I'm going to refrain from providing details.

Sorry and thanks!