Re: vtnet is still slow

Reply: void : "Re: vtnet is still slow"
In reply to: void : "vtnet is still slow"
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From: Cheng Cui <cc_at_freebsd.org>
Date: Wed, 22 Oct 2025 18:27:33 UTC
Interesting, my Bhyve host node "n1" and my MacbookProM1 laptop are wired to the same 1Gbps home switch.

The "n1" runs FreeBSD stable/14-9e40b536cb58 and Bhyve, with ethernet port re0. The "n1fbsd15x" VM runing FreeBSD stable/15-01a653205313 is a guest in "n1" with vtnet0 port. All sysctl values in default.

The iperf3 "iperf3 -c laptop -i1 -t10" traffic sent from the "n1fbsd15x" VM to my laptop:
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[  5]   0.00-1.08   sec  89.5 MBytes   695 Mbits/sec   37    501 KBytes       
[  5]   1.08-2.08   sec   112 MBytes   946 Mbits/sec    0    759 KBytes       
[  5]   2.08-3.08   sec   113 MBytes   946 Mbits/sec    0    949 KBytes       
[  5]   3.08-4.07   sec   111 MBytes   943 Mbits/sec    6   5.66 KBytes       
[  5]   4.07-5.07   sec   112 MBytes   941 Mbits/sec    0    705 KBytes       
[  5]   5.07-6.01   sec   106 MBytes   941 Mbits/sec    0    817 KBytes       
[  5]   6.01-7.07   sec   119 MBytes   942 Mbits/sec    0    915 KBytes       
[  5]   7.07-8.07   sec   112 MBytes   942 Mbits/sec    0    984 KBytes       
[  5]   8.07-9.07   sec   112 MBytes   942 Mbits/sec    0   1.01 MBytes       
[  5]   9.07-10.07  sec   113 MBytes   941 Mbits/sec    0   1.04 MBytes       
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.07  sec  1.07 GBytes   916 Mbits/sec   43            sender
[  5]   0.00-10.08  sec  1.07 GBytes   914 Mbits/sec                  receiver

iperf Done.

My Bhyve setup: https://wiki.freebsd.org/chengcui/install_FreeBSD13_VM_via_bhyve

> On Oct 22, 2025, at 10:03, void <void@f-m.fm> wrote:
> 
> Hi,
> 
> I wondered if any work was happening to address the long-standing issue
> of slow vtnet? (in my case, this leads to slow freebsd guest performance
> in bhyve compared with every linux guest tested and OpenBSD).
> 
> I thought maybe the recent bridge work may have ameliorated the problem some, but testing, after configuring a (recent) stable/15 server to use the ip-configured-on-bridge-method, showed no improvement using
> a (recent) stable/14 guest
> 
> [ ID] Interval           Transfer     Bitrate         Retr
> [  5]   0.00-60.03  sec  3.17 GBytes   454 Mbits/sec    0     sender
> [  5]   0.00-60.03  sec  3.17 GBytes   454 Mbits/sec          receiver
> 
> for comparison, an ubuntu 25.04 guest:
> 
> [ ID] Interval           Transfer     Bitrate         Retr
> [  5]   0.00-60.00  sec  6.42 GBytes   919 Mbits/sec  5427    sender
> [  5]   0.00-60.00  sec  6.42 GBytes   919 Mbits/sec          receiver
> 
> the baremetal host
> 
> [ ID] Interval           Transfer     Bitrate         Retr
> [  5]   0.00-60.01  sec  6.58 GBytes   941 Mbits/sec    0     sender
> [  5]   0.00-60.01  sec  6.58 GBytes   941 Mbits/sec          receiver
> 
> Tests done a year and a half ago on similar hardware showing
> the same patterns http://void.f-m.fm.user.fm/bhyve-virtio-testing.html
> -- 
> 

Best Regards,
Cheng Cui