IPv6 BGP & kernel 4.19

[Oliver]

Hello,

after upgrading to debian buster with kernel 4.19 we also had problems.

By adjusting net.ipv6.route.max_size we have fixed the following messages:
watchdog: BUG: soft lockup - CPU#X stuck for 22s! 
and
ixgbe 0000:02:00.0 ens2fX: initiating reset due to tx timeout

But we still had a lot of jitter on the line. Downgrading to 4.9.0 fixed the
problem, but this is not a permanent solution.

What else did we tried:
* Increasing gc_threshX
net.ipv6.neigh.default.gc_thresh1 = 2048
net.ipv6.neigh.default.gc_thresh2 = 4096
net.ipv6.neigh.default.gc_thresh3 = 8192
=> Did not help

* Going to a backports kernel (5.7.0)
=> Did not help

@Frederik Kriewitz: What did you do fix that problem?

Oliver