[OpenAFS] broken callbacks

[Benjamin Kaduk]

On Wed, 20 Apr 2016, Andreas Hirczy wrote:

>
>    I'd rather prefer not to increase -cb, since this seems to be not our
>    usual usage pattern.

Increasing -cb is pretty cheap; IIRC it's about 32 bytes of memory per
callback, and the runtime overhead only comes into play at shutdown.

My draft change to auto-tune fileserver parameters for a target memory
footprint at https://gerrit.openafs.org/#/c/11629/ just uses all the
remaining memory footprint after the other parameters are tuned for
callbacks.  The openafs servers are very bad at making full use of the
hardware resources available; increasing callbacks is one way to make a
more effective use of resources.

-Ben

P.S. if anyone wants to review and/or test that gerrit change, that would
be great!