Sorry for being slow to respond, but it took some reading, re-reading, and digesting of your excellent post to get to this point.
I appreciate your clearing up at least some of the mystery about RAM, swap files, and their interaction, and while I'm not certain that I've reached the "
By George…" stage, I
do think I've got it, and that these lines sum the issue up:
Depending on the needs of the individual application additional Virtual addresses will be mapped to … Swapfiles on the hard drive (whether they are actually used or not) (Emphasis added)
How much address space is mapped to the swapfile(s) depends on the memory management algorithms in the OS, and the actual requirements of the programs.
…the OS may elect to map a portion of the virtual address space requested by an application to the swapfile to speed up the initial page out when required. How much of this virtual address space is mapped to the swapfiles is dependent on the memory allocation algorithms in the OS and to how the application code is written.
Or, to put it in terms of my experience,
- swapfile0…created at boot is OS X's default anticipation that swap space may be required and that xMB is a reasonable starting point.
- What was happening in my examples is that OS X/the programs in question/both anticipated a greater need than swapfile0 allowed for and created swapfile1 against the possibility.
- Since I've maxed out my RAM, the additional real memory has negated at least part of the potential need for virtual memory, so swapfile1 is no longer created.
I think, i.e. hope, that-all's more or less on the mark.
I'm wondering, though, whether your
It does appear from practical experience, later versions of OS X are being more frugal with swapfiles and mapping less swapfile space until it is actually required.
is contradicted by tacit's
Right now, I have one swap file that's 1 GB in size….
because
swapfile0 in OS X 10.6.8 is only 67.1MB. (I'm assuming that tacit's file is
swapfile0 in OS X 10.9.x.)?
