freebsd stable - Apr 2020 - CFT: if_bridge performance improvements

??, 14 ???. 2020 ?., 12:51 Kristof Provost <kp at freebsd.org>:
> Hi,
>
> Thanks to support from The FreeBSD Foundation I?ve been able to work
> on improving the throughput of if_bridge.
> It changes the (data path) locking to use the NET_EPOCH infrastructure.
> Benchmarking shows substantial improvements (x5 in test setups).
>
> This work is ready for wider testing now.
>
> It?s under review here: https://reviews.freebsd.org/D24250
>
> Patch for CURRENT: https://reviews.freebsd.org/D24250?download=true
> Patches for stable/12:
> https://people.freebsd.org/~kp/if_bridge/stable_12/
>
> I?m not currently aware of any panics or issues resulting from these
> patches.
>
> Do note that if you run a Bhyve + tap on bridges setup the tap code
> suffers from a similar bottleneck and you will likely not see major
> improvements in single VM to host throughput. I would expect, but have
> not tested, improvements in overall throughput (i.e. when multiple VMs
> send traffic at the same time).
>
> Best regards,
> Kristof
>
Hi!
Thank you for your work!
Do you know if epair suffers from the same issue as tap?
>

On 16 Apr 2020, at 8:34, Pavel Timofeev wrote:
> Hi!
> Thank you for your work!
> Do you know if epair suffers from the same issue as tap?
>
I?ve not tested it, but I believe that epair scales significantly 
better than tap.
It has a per-cpu mutex (or more accurately, a mutex in each of its 
per-cpu structures), so I?d expect much better throughput from epair 
than you?d see from tap.

Best regards,
Kristof