> The only thing missing is an option that you could claim a swap space as designated for only allowing tmpfs spillover.
You have this option — use a separate ext3 partition. :)
> we do often generate lots of temporary files (for sorting or graphing) and some might actually be rather large.
Why do you use tmpfs then? You can just use regular disk. Have you noticed some speedup because of using tmpfs?
> Tmpfs really is the most sane option for /tmp. Why bother doing cleanups at boot?
Why bother about tmpfs size? Why bother about adding more swap. Why bother about system slowed down because of heavy swap usage? On-disk /tmp don't have these problems. And it's cleaned on boot automatically anyway, no need to bother.
> Why bother guaranteeing on disk-consistency or doing disk flushes on sync/fsync/fdatasync.
Nobody does fsync in /tmp, so nobody bothers. :)
> The only sane alternative would be a ext2 filesystem with all data guarantees turned off and recreating it every time you boot.
That's why ext3 is better. Replaying ext3 journal is faster than creating a new filesystem.