> No. The big difference is that regular filesystems try to do I/O to their backing device - heck that is their point, and what they do the vast majority of the time. tmpfs does not do any I/O. However I/O will happen when there is memory pressure by the swapper, but that is going to be rarer.
Yes and no - aren't they just two ways of looking at the same decision? Regular filesystems will buffer, and when the system is low on memory it will flush buffers, using similar criteria to deciding whether to swap.
> Swap can also be used for actual swap on the occasions it is helpful.
Swap enables actual swap, sure. My experience is that it usually hurts more than it helps though.
> ... Regular filesystems will buffer, and when the system is low on memory it will flush buffers ...
That is the bit you are missing. Unwritten filesystem data is regularly flushed. The flush interval is often around 5 seconds. Lookup "pdflush" to get the gist, although things have changed since then. Same with laptop mode.
Quite simply if a file is created and lives for at least N seconds then there will be disk activity irrespective of memory pressure. N is 5, perhaps up to 30 seconds in normal use.
Even if the file contents aren't fully flushed, metadata is.
Yes and no - aren't they just two ways of looking at the same decision? Regular filesystems will buffer, and when the system is low on memory it will flush buffers, using similar criteria to deciding whether to swap.
> Swap can also be used for actual swap on the occasions it is helpful.
Swap enables actual swap, sure. My experience is that it usually hurts more than it helps though.