[OpenAFS] Tuning openafs write speed

[Harald Barth]

> memcache is much faster than the disk cache.  memcache will not get any
> better if no one ever uses it so the openafs developers can get some
> bug reports.

When we got out last system, the group at PDC decided that
non-swappable/pageable memory was a too expensive resource to be used
for file cache. If calc users buy a machine with 32GB of RAM they
expect that _at_least_ 32GB of RAM can be used for caculations. Yeah,
they are that way ;-). So for example taking 3GB (10%) is not
acceptable if it can not be swapped out.

If the memcache would be swappable (I'm talking about Linux, because
calc users use Linux), that would be a completely other matter.

Harald.