On 22 Apr 2020, at 18:15, Xin Li wrote:
On 4/22/20 01:45, Kristof Provost wrote:
On 22 Apr 2020, at 10:20, Xin Li wrote:
Hi,

On 4/14/20 02:51, Kristof Provost wrote:
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.

I have observed the following panic with latest stable/12 after applying the stable_12 patchset, it appears like a race condition related NULL
pointer deference, but I haven't took a deeper look yet.

The box have 7 igb(4) NICs, with several bridge and VLAN configured
acting as a router.  Please let me know if you need additional
information; I can try -CURRENT as well, but it would take some time as the box is relatively slow (it's a ZFS based system so I can create a separate boot environment for -CURRENT if needed, but that would take some time as I might have to upgrade the packages, should there be any
ABI breakages).

Thanks for the report. I don’t immediately see how this could happen.

Are you running an L2 firewall on that bridge by any chance? An earlier version of the patch had issues with a stray unlock in that code path.

I don't think I have a L2 firewall (I assume means filtering based on
MAC address like what can be done with e.g. ipfw?  The bridges were
created on vlan interfaces though, do they count as L2 firewall?), the
system is using pf with a few NAT rules:


That backtrace looks identical to the one Peter reported, up to and including the offset in the bridge_input() function. Given that there’s no likely way to end up with a NULL mutex either I have to assume that it’s a case of trying to unlock a locked mutex, and the most likely reason is that you ran into the same problem Peter ran into.

The current version of the patch should resolve it.

Best regards,
Kristof
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