This seems to be a different machine.
The mount default for a tmpfs file system is 50%
The first machine had a pup_rw (writable layer) of 501M
This pup_rw is about 1G
The size is just an arbitrary number.
The size of the tmpfs depends on the space taken by the files.
With no files, the tmpfs takes almost no space.
The tmpfs is supposed to expand and contract to fit the space taken by the files.
On a machine with 1G, a tmpfs of 500M max
leaves 500M of ram free even with the tmpfs completely full.
nearly 1G of ram free for an almost empty tmpfs.
du shows pup_rw (the save layer in ram)
is using about 51M and /tmp/ is using about 8M
These are perfectly normal values for Puppy.
Why the discrepancy with df I'm not sure.
If a file that is being used is deleted,
the name of the file is removed from the file system,
but all the rest of the file stays in the FS (inodes,data,etc)
That part will be deleted if and when the file is released.
Until the file is completely deleted, it will continue to take space in the FS.
That space will not be visible to du
Not sure about Precise, my Pup copies the sfs files to the tmpfs.
That uses 500M or so of ram space.
I don't think the sfs files were copied to the tmpfs.
WARNING: RAM working space only 1MB
That sounds like a message from Puppy.
It specifically refers to ram working space.
So, it doesn't seem to be running out of inodes.
Do you run servers, like html or ftp or even Samba?
Servers often need the numbers of files allowed, to be tweaked.
Samba logs may periodically need deleting.
Should show up by du
Viruses can cause strange things to happen.