OK, for those still interested in this subject, I am trying to figure out a few things, and as usual having some difficulty.
The fstab entry for /tmpfs apparently determines the MAX size the temp can be.
When used with Defaults in the fstab line that means half of the recognised memory in the system.
You can also manually determine the size of the temp fs by replacing 'defaults' with a size ..... size=256m .... for instance.
Your temp is now limited to 256MB!
What I was trying to achieve is that my temp fs would use that 256MB until filled, and then begin to use the Swap space available for anything extra.
That does not happen automatically, so obviously some more must be done ...... but what?
One answer would appear to be to make the temp fs entry in fstab equal to half of the fitted RAM, plus a large proportion of the Swap space.
So if I have 4GB Swap, and 4GB RAM, I could make the temp fs size=3g ..... that should now ensure that if /tmp runs out of RAM it will use Swap in addition.
Of course what I would like to do is to allocate 256MB of RAM only, and make the max size of the temp fs 1256m
So now I look at the other entries in fstab, and notice this 'none' entry.
What does that do?
Is that the entry that limits the RAM that can be used?
I have not yet found sufficient information to determine what exactly this is doing ....... so if anyone has ideas please post, thanks.