Ridiculous idea: Cache as ramdisk?

[ibotty]

> On solaris and now linux, tmpfs is just that. If it starts to compete with
> applications for memory, it will push writes out to swap. So it only uses
> as much memory/swap space as what you put in swap.

as far as i understood the original poster, he wants two things:

a) he (and me too) wants a huge buffer cache per filesystem, that has the
criterias, that kip macy illustrates for tmpfs.

i guess it is important for this scheme to have (one buffer cache)
filesystem, because you may treat /usr differently  than 
/my_big_fat_static_data_partition, but i am not sure if with more than one
cache overhead is an issue.

b) he wants a possibility to retain a specific file in the cache.
this can be generalized to the idea, that each file has different
buffer-cache priority.

this surely would be nice i fear, it would be, but overhead comes into play
again.

apart from this, i like this approach very much.

~ibotty