Tuning suggestions for high-core-count Linux servers

[Ray Bellis]

On 01/06/2017 23:26, Mathew Ian Eis wrote:

> … and for one last really crazy idea, you could try running a pair of
> named instances on the machine and fronting them with nginx’s
> supposedly scalable UDP load balancer. (As long as you don’t get a
> performance hit, it also opens up other interesting possibilities
> like being able to shift production load for maintenance on the named
> backends).

It's relatively trivial to patch the BIND source to enable SO_REUSEPORT
on the more recent Linux kernels that support it (3.8+, ISTR?) so that
you can just start two BIND instances listening on the exact same ports
and the kernel will do the load balancing for you.

For a NUMA system, make sure each instance is locked to one die, but
beware of NUMA bus transfers caused by incoming packet buffers being
handled by a kernel task running on one die but then delivered to a BIND
instance running on another.

In the meantime we're also looking at SO_REUSEPORT even for single
instance installations because it appears to offer an advantage over
letting multiple threads all fight over one shared file descriptor.

Ray