| 1 | swapinfo |
| 2 | ======== |
| 3 | |
| 4 | Swapinfo is designed to provide some information to the user about the |
| 5 | state of the swap space on the system. I've written it based on a |
| 6 | brief (!) perusal of the VM code in 386BSD. I could be pretty confused |
| 7 | about how it all fits together, and perhaps this is totally bogus. |
| 8 | It seems to work for me, though. |
| 9 | |
| 10 | How it works: |
| 11 | |
| 12 | During startup, the system traverses the list of configured swap partitions, |
| 13 | and determines the size of the various partitions. As each new partition |
| 14 | is added for swapping (via swapon), the free space on that disk is added |
| 15 | to a linked list of free space. Adjacent areas are coalesced to form |
| 16 | larger areas. The swapping algorithm seems to take the first free section |
| 17 | that it finds [?]. |
| 18 | |
| 19 | Swapinfo reads in the list of configured swap partitions from the /dev/kmem, |
| 20 | to determine the size of the partitions. It then traverses the list |
| 21 | of free space, figuring up how much is still available and how much |
| 22 | has therefore been used. Things get a little hairy in that the swap space |
| 23 | is divided amongst the configured swap partitions so that the first |
| 24 | 4096 blocks of swap go on the first swap partition, the second 4096 on |
| 25 | the second swap partition, and so on. This works out to be a fairly |
| 26 | simple bit of code, though. |
| 27 | |
| 28 | More caveats: |
| 29 | |
| 30 | This works on my system. Your milage may vary. Since I'm reading /dev/kmem |
| 31 | to follow a linked list, the program could easily get lost looking for |
| 32 | some free space if anything got changed between reads of /dev/kmem. |
| 33 | If you get occasional inconsistant results, ignore 'em. |
| 34 | |
| 35 | Feel free to send bug reports, flames, etc., to: |
| 36 | |
| 37 | Kevin Lahey |
| 38 | kml@rokkaku.atl.ga.us |